Developmental psychology

Developmental psychology

1. Dynamic epigenetic

   • Development is a dynamic process shaped by the interactions between genes and environments.  Within the field of developmental biology, the complex interactions between genes and their products that create the foundation for cellular differentiation and the formation of the nervous system have been well described.
   • Advances in molecular biology have permitted increasing precision in the characterization of the cascade of molecular changes that link genes to specific developmental endpoints.
   •  However, beyond addressing questions regarding the processes linking a gene to a phenotypic outcome, description of these molecular changes has also provided insight into the ways in which the environment induces lasting biological effects
   • Though environments – particularly characteristics of the social world around us – are typically viewed as a separate and distinct influence from genes, there is increasing understanding of the interplay between genes and environments.
   • Brain development
     • The prenatal period is a time of rapid brain development and sets the stage for later emerging outcomes in infancy and beyond.
     • Prenatal maternal exposure to toxins, variation in nutritional environments, and stress can impact the developing fetal brain either through direct exposure to the environmental agent or indirectly via dysregulation of placental function or maternal physiology
     • These pathways are not mutually exclusive and it is likely the case that disruption to fetal development and infant outcomes is the product of additive and interactive direct and indirect exposure effects
     • prenatal nutrition, drugs/toxins, maternal stress
     • Demonstrations of epigenetic inheritance may also be restricted to these artificial contexts – or modulated by genetic and environmental factors under more naturalistic conditions
     • Epigenetics
       • These modifications have implications for the expression of genes that shape neurodevelopment, health, and behavior, and have been hypothesized to be the mediators between the environment and phenotypic outcomes
       • The malleability of epigenetic mechanisms in early development, coupled with the knowledge of early life sensitive periods, has resulted in increasing integration of epigenetics in the study of infancy.
       • The broad application of epigenetics within developmental biology, environmental sciences, psychology, and psychiatry has highlighted the converging biological pathways through which experiences, particularly those occurring early in development, can exert a lasting impact 
       • direct effects and lasting generational effects of environment
       • there are currently three general types of molecular changes that impact gene regulation and are malleable in response to environmental experiences: DNA methylation, histone modifications, and noncoding RNA
       • epigenetic plasticity in response to interventions is being increasingly demonstrated. For example, prenatal effects of smoking on DNA methylation and asthma risk can be significantly ameliorated using vitamin C supplementation during pregnancy
       • Gene-environment interactions
         • The concept of gene–environment interactions has become ingrained within the developmental sciences and more broadly in the biological and social sciences.
         • The general principle of a gene–environment interaction is that genes may predict phenotypic outcomes – such as behavior, growth, or health – but the predictive utility of genes is moderated by the types of environments to which an individual is exposed
         • Gene–environment interactions also provide insights into the conditions under which an environment would impact phenotypic outcomes
         • The simple theoretical conclusion of studies indicating a gene–environment interaction is that the prediction of phenotypic outcomes is likely to be enhanced by knowing about both the genetic and environmental characteristics of an individual
         •  However, the study of gene–environment interactions is methodologically far from simple and can yield effects that are challenging to replicate due in part to the broad definitions of gene (e.g., twin studies, candidate genes, genome-wide DNA sequencing) and environment (e.g., socioeconomic status, exposure to trauma, nutrition) and the occurrence of correlations between genes and environmental exposures
         • he role of contextual variables for the transmission of environmentally induced epigenetic changes across generations also requires careful consideration. Though experimental studies in rodents allow us to control genetic and environmental conditions as a strategy for creating optimal conditions for characterizing cause–effect relationships, these manipulations also create an artificial context for development and reproduction
         • Social environment
           • The social context of development can have enduring effects on a child. Initial observations of the association between parent–offspring separation, infant distress, and impairments in the parent–offspring social relationship have been coupled with decades of work in humans, primates, and rodents illustrating the impact of mother–infant social interactions on brain development and behavior.
           • Mammalian development during postnatal development is shaped by variation in the quality and frequency of caregiver contact. In humans, deprivation of postnatal parental care through institutionalization results in increased rates of symptoms of ASD, poorer social engagement, attentional deficits, and hyperactivity 
           • Brain changes associated with institutional rearing include significant reductions in prefrontal cortex and hippocampal volume, increased positive coupling of activity between the ventral striatum and prefrontal cortex , and broad changes in connectivity within brain networks critical for cognitive functioning 
           •  Comparison of children who remain institutionalized and those who are placed in nurturing foster homes indicates that deficits in social and cognitive functioning can be ameliorated
           • Disruptions to the early child–parent relationship in the form of abuse and neglect increase risk of psychopathology, alter immune and neuroendocrine function, and impact brain structure and function
           • Environmental conditions that impact these contexts of early development are well poised to exert lasting epigenetic effects in offspring. Studies in rodents suggest that these maternal effects can also be propagated to the next generation
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             • The interplay between genes and environments is a fundamental feature of development and advances in our understanding of epigenetic mechanisms and their malleability have promoted a more integrated perspective on this interplay
             • In humans, evidence for epigenetic effects of prenatal and postnatal environments and their association with infant outcomes is continuing to grow, extending to global epigenomic outcomes and multigenerational effects
             • Though epigenetic analyses in humans are not typically conducted in the brain, the value of epigenetic biomarkers in peripheral tissues for predicting neurodevelopmental outcomes is evident
             • Future directions of this work include bridging the mechanistic gap between the occurrence of peripheral epigenetic changes and brain structure/function, expanding our understanding of the epigenetic consequences of nurturing/healthy environments, and integrating sociocultural/contextual factors into the analyses of environmentally induced epigenetic changes emerging during infancy and childhood.
     • DNA methylation
       • Among the nucleotides that create the DNA sequence, cytosines can become chemically modified through the addition of a methyl group This process is referred to as DNA methylation and serves a critical role in cellular differentiation
       • The methylation of cytosines within DNA can lead to long-term gene silencing, though the location of the methylated DNA and other contextual factors may determine the ultimate impact that DNA methylation has on gene expression
       • in addition to DNA methylation, epigenetic regulation of genes can be achieved through chemical modification of histone proteins and altered expression of noncoding RNAs
       • In the case of noncoding RNAs, the epigenetic regulation of gene function can occur both at the level of transcription (DNA to mRNA) and translation (mRNA to protein)
       • Among 3–5-year-olds, childhood maltreatment (abuse/neglect) is associated with altered DNA methylation of the FK506 binding protein 5 (FKBP5) gene – which plays a critical role in the neuroendocrine response to stress – and these effects interact with degree of contextual stressors such as separation from a caregiver, housing instability, and neighborhood violence
     • Maternal stress
       • There is an expansive literature on the effects of maternal stress during pregnancy on offspring development in animals and humans, with outcomes being observed prenatally and persisting across the life span
       •  Similarly, human studies of prenatal stress include measures of self-report perceived stress, elevated glucocorticoids, exposure to trauma, exposure to famine, and maternal psychopathology (primarily anxiety and depression). 
       • There are likely unique effects on offspring development specific to exposure type and diverse pathways through which each of these exposures lead to biological change in offspring
       • Preterm birth is a risk factor for poorer neurodevelopmental outcomes, including a heightened risk of autism spectrum disorder (ASD), attention deficits, and cognitive impairment  These deficits may be the consequence of altered connectivity between brain regions and a delayed maturation of white matter tracts
       • Epigenetic changes within the placenta, fetus, and infant as a consequence of both prenatal stress and preterm birth have been observed
       • moreover, mediation analyses indicate that stress-associated placenta epigenetic changes statistically mediate the effects of maternal stress on offspring brain development
       • intriguing evidence – drawn primarily from rodent studies – that the preconception experiences of fathers can exert intergenerational and transgenerational effects on offspring development through epigenetic transmission
       • BDNF
         • The BDNF gene plays a critical role in neural plasticity and facilitates emotional and cognitive development. This epigenetic effect of in utero BPA on BDNF is only observed in males – an indication of sex differences in the epigenetic effects of exposures – and may explain the particular vulnerability of males to BPA-associated behavioral changes in childhood
         • including increased emotionally reactive and aggressive behaviors
         • Maternal levels of the endocrine disrupting chemical bisphenol A (BPA) are associated with altered DNA methylation levels within the brain-derived neurotrophic factor (BDNF) gene in cord blood samples taken at the time of birth, such that high levels of maternal BPA are associated with increased BDNF DNA methylation
         • During infancy, outcomes associated with prenatal stress can include poorer sleep quality, increased anxiety, and reduced cognitive ability. One of the challenges posed by this literature is the very broad definition of stress

2. Development During Infancy in Children Later Diagnosed ASD

   • Autism spectrum disorder (ASD) is a heritable, heterogeneous, and common neurodevelopmental condition defined by impairments in social communication alongside restricted and repetitive behaviors
   • ASD is a moving target; its definition has changed dramatically over the years
   • The first comprehensive clinical descriptions of the condition were given by Leo Kanner and Hans Asperger more than 70 years ago  but it was not before 1980, with the publication of the third edition of the Diagnostic and Statistical Manual (DSM) of the American Psychiatric Association that the term autism was introduced as a formal category
   • At that time, only one criterion related to social interaction was listed (pervasive lack of responsiveness to other people).
   • ASD
     • Clinically, another outstanding and blurring factor is the high rates of co-occurring conditions (e.g., with intellectual disability, attention-deficit hyperactivity disorder [ADHD], language disorder, motor problems). 
     • ASD is also etiologically diverse, with a primary role for a range of genetic factors but also potential interactions with environmental exposures.
     • Further, because ASD is very likely to reflect atypicalities in to the early development of the brain, longitudinal studies of infants are required to fully understand its emergence
     •  The sharp increase in research focusing on early development during the last 15 years is largely due to the demonstration that it is feasible and fruitful to study infant siblings of children with the condition in prospective longitudinal studies
     • sensory hypersensitivity (intolerance to touch etc), motor development (correlate high symptoms), language, executive function
     • Infant sibling design
       • The primary strength of the infant sibling design is that it allows for systematic, longitudinal and (relatively) unbiased assessment of specific constructs putatively related to ASD
       • Such data are needed to inform our theories of neurodevelopmental trajectories “leading to” the diagnosis and to identify the developmental periods with maximal endo-phenotypic homogeneity
       • which may enable us to develop screening tools or biological markers with improved sensitivity and specificity
       •  Typically, a sib study recruits infants with an older sibling with ASD, with a first assessment before the infant’s first birthday
       • Categorical diagnostic judgments made by experienced clinicians based on gold-standard instruments like the Autism Diagnostic Observation Schedule and the Autism Diagnostic Interview – Revised are typically complemented by continuous measure
       • In the categorical analysis, the researcher typically compares three main outcome groups: (1) high-risk siblings with ASD diagnosis at follow-up, (2) low-risk infants (without ASD diagnosis), and (3) high-risk infants without ASD diagnosis
       • Neurodevelopmental processes
         • Parental reports of perceptual sensitivity (a temperamental measure) at 6 months and early parent concerns about sensory problems
         • Although relatively little is known about the neural correlates of altered sensory processing in infancy, brain atypicalities emerging early in development are likely to reflect or cause atypicalities in sensory processing, as the sensory networks are formed during this period and depend on the integrity of the underlying neural systems
         • Social attention
           • Social attention refers to the general tendency to prioritize social information over nonsocial information
           • According to one hypothesis, early problems with social attention – due to atypical development of subcortical neural pathways – cause infants with later ASD to orient less to faces and therefore get less learning opportunities in the social domain early in life 
           • social interaction appears relatively intact in the first few months for infants with later ASD. For example, perturbations of social interaction as studied in the “still face” paradigm appear to have the same effects on interaction in infants with and without later ASD
           • In contrast, there seems to be more clear evidence for impaired tendency to initiate joint attention between 8 and 18 months as a predictor of later ASD
           • Such work indicates that infants with later ASD show relatively typical interactions with their parents at 6 months, but by 12 months show reduced levels of mutuality in the interaction, positive affect, and attentiveness
           • Executive function
             • finding that slower developmental change in the duration of individual looks to faces was apparent in high-risk relative to low-risk infants, and predicted poorer later executive functioning
             • So far, there is very little available research on emerging executive function (EF) in infants at risk for ASD. One exception is St. John et al. (Reference St. John, Estes, Dager, Kostopoulos, Wolff, Pandey and Botteron2016) who studied the A-not-B task in infants at risk for ASD; this task reflects – at least in part – individual differences in simple inhibition. It was found that performance improved less in the high-risk group compared to the low-risk group between 12 and 24 months of age, but this effect was not linked to later diagnostic status
             •  Indeed, problems with visual disengagement are among the most replicated infant markers of ASD. Still, the findings are not entirely consistent when it comes to the onset of this putative atypicality in ASD and how the dependent variables are defined
             • biological motion - may be considered consistent with reduced attention engagement to faces during infancy in ASD.
         • Language
           • Several prospective studies of high-risk infants have identified delays in understanding language by 12 months of age in infants later diagnosed with ASD 
           • Several prospective studies of high-risk infants have identified delays in understanding language by 12 months of age in infants later diagnosed with ASD 
           • In parallel with poor language comprehension, language production is also atypical in infants that develop ASD
           • Specifically, high-risk infants later diagnosed with ASD or who had other sociocommunicative delays produced fewer “middle” consonant types at 6 months, fewer “late” consonant types at 9 months, and a lower total number of different consonant types at 12 months than high-risk infants with typical outcomes
           •  these findings may suggest difficulty with each new stage of language production in infants with later ASD, although the specificity to ASD is unclear
           • An important future direction for this area is to understand the neural mechanisms that may underpin early language delays within autism, and whether these are the same or distinct from those observed in infants with other language delays
         • Brain development
           • First, one study has delineated patterns of early overgrowth of gray matter regions that are somewhat consistent with earlier reports of accelerated head growth from circumference measures in infancy
           • Regions with a particularly large expansion in surface area included primary visual areas, and frontal and temporal areas of the “social brain.” Individual differences in the degree of overgrowth were linked to the emergence and severity of social difficulties related to ASD.
           • Another measure that could contribute to early increased head circumference is an excess of cerebrospinal fluid (CSF) in the subarachnoid space. Two recent studies have shown that infants with later ASD had significantly greater extra-axial CSF volume at 6 months that persisted through development - The accumulation seemed most pronounced in the frontal cortex
           • The result suggests that in addition to the structural atypicalities observed in the same cohort , alterations in how brain regions communicate with each other could underpin the later emergence of behavioral challenges associated with ASD
           • Replicability
             • One key challenge facing the field as it matures is to begin to complement exploratory studies that generate new leads with robust replications in large samples with preregistered analytic plans
             • Braukmann et al. (Reference Braukmann, Lloyd-Fox, Blasi, Johnson, Bekkering, Buitelaar and Hunnius2018) replicated earlier reports of reduced specialization for social stimuli in the temporal lobe in a new cohort of 5-month-old high-risk infants (Lloyd-Fox et al., Reference Lloyd-Fox, Blasi, Elwell, Charman, Murphy and Johnson2013); and Haartsen, Jones, Orekhova, Charman, and Johnson (Reference Haartsen, Jones, Orekhova, Charman and Johnson2019) have recently replicated the observation that increased connectivity at 12 months 
             • Increased efforts to replicate results in other samples will be an important step towards refining our understanding of early ASD
             • Given the heterogeneity of ASD, building large samples is essential to enabling better powered analyses that allow the potential stratification (identification of subgroups) of different developmental paths 
             • To date, the majority of studies in the field focus on examining group-level effects that relate to ASD as a single category. However, it is becoming increasingly recognized that group-level insights do not necessarily apply at the level of the individual.
             • While the heterogeneity within the ASD population is likely to have a strong biological basis, sociocultural factors may influence how the core symptoms are expressed and their consequences for psychological well-being and participation in society
             • Future research
               • We now know that early signs of ASD are first rather subtle, and barely noticeable for the naked eye (even a trained clinician’s eye), but that underneath the surface, at the level of brain structure and function, atypical processes unfold that predict the later development of core ASD symptoms or a full clinical diagnosis.
               • Distributed atypicalities in more general aspects of brain development appear to be more suitable to explain the pattern of results.
               • comparing sibling studies to other measures, types of studies, Increasing Robustness and Replicability Through Large-Scale Multisite Studies
               • Toward Causation: Embedding Intervention in the Sibling Design -  Ethical, Sociocultural, and Policy Perspectives
               • As our understanding of the early mechanisms leading to ASD deepens, the field must move to develop new therapeutic and support strategies for families. The hope is that one can develop interventions that boost adaptive skills and prevent the emergence of longer-term cascading difficulties
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                 • Given that longitudinal studies of infants at risk are very resource demanding, a justified question is: is it worth the effort?
                 • Being the devil’s advocate, one may point out that some of the general conclusions we adhere to today, such as the fact that onset patterns of ASD are heterogeneous and involve multiple domains (including but not restricted to social function), were the exact main conclusions of the retrospective report described at the outset of our chapter
                 • This study was published more than 30 years ago, before anyone had come up with the idea of studying infant siblings. At the same time, we clearly have a much more detailed picture of the most relevant developmental processes now than one had at that time
                 • Arguably, the single most important advance is the demonstration of atypical structural and functional brain development during infancy in individuals with ASD
                 • If coupled with other informative designs and approaches, the infant sibling design will be an increasingly valuable source of information about ASD, related conditions, and the large variability in human development more generally.

3. Visual development

   • Nevertheless, missing visual input near birth because of dense cataracts in one or both eyes alters the developmental trajectory, even when treatment occurs within the first few months of life. 
   • Thus, the early visual input, despite its limitations, is critical for setting up the neural architecture for later refinement.
   • Variations in diet affect the postnatal development of the retina and hence lead to cross-cultural variations in the quality of visual input
   • The initially poor vision of the newborn arises largely from an immature retina. In adults, the perception of fine detail and low contrast is mediated by the fovea, the central region of the retina that is densely packed with cones that efficiently transmit light. In newborns, the transmission is estimated to be 350 times less efficient than in adults
   • On the other hand, extra-visual experience because of premature birth does not lead to any advantage: Acuity and binocular vision develop based on gestational age,
   • Newborns visual perception
     • low level vision: acuity,  To measure newborns’ vision, the test is adapted to take advantage of infants’ preference to look at something patterned over something plain
     • Contrast Sensitivity  Newborns’ sensitivity to contrast has been tested with a method similar to the acuity test, but now, during each block, the stripes remain the same size over trials, but their contrast is systematically reduced.
     • Peripheral Vision and Stereopsis sensitivity to smaller and dimmer stimuli continues to improve into middle childhood. Moreover, throughout infancy, babies respond to peripheral stimuli much less frequently if the stimulus is static rather than flickering
     • Despite these limitations, early visual experience is critical for later visual development. The clearest evidence comes from children who were born with cataracts in both eyes that blocked all patterned visual input until the cataracts were removed surgically and the eyes fit with compensatory contact lenses
     • On the other hand, extra-visual experience because of premature birth does not lead to any advantage
     • Cultural variations
       • Cultural variations in diet may influence the baby’s visual development because of the influence of long-chain polyunsaturated fatty acids in the mother’s diet during pregnancy, in the mother’s breast milk, or included as an additive to the baby’s formula
       • The levels of ARA and DHA in breast milk vary cross-culturally over a 4-fold and 18-fold range, respectively -  Levels are higher in societies where fish is a regular part of the diet
       • Together, the evidence on the effect of diet suggests that there may be considerable variation cross-culturally in retinal and visual cortical development and the fine visual resolution they come to mediate
       • Newborns are known to differ in the quality of the visual input they receive with which to build their cortical circuitry – the quality is lower for babies born preterm or with peripheral visual perturbations like cataracts
       • Although these differences are small and there is considerable overlap in acuity between groups, in animal (rodent) models the changes effected in neurotransmitters from inadequate diets are not reversible 
       • Higher-Level Vision
         • Newborns fail most tests of sensitivity to motion, whether tested for sensitivity to the direction of motion with visually evoked potentials or with preferential looking.
         •  For example, when shown a stimulus with uniformly moving dots versus a stimulus in which a form is defined by dots moving in a direction opposite the background, infants show no preference to look at the motion-defined form before 7 weeks of age and then do so only for a restricted range of velocities
         • The slow development of sensitivity to direction of motion contrasts with the earlier development of sensitivity to the orientation of stationary stimuli
         • The limitations in sensitivity to motion likely reflect immaturities in the primary visual cortex and the retinal input it receives since it is the first cortical way station where individual neurons are tuned to direction
         • Children who missed early visual input because of dense cataracts in one or both eyes later have only small deficits in processing the direction of motion in sine wave gratings when local cues are sufficient and no global integration is required
         • However, when global integration is required because only some dots are moving coherently in the same direction while the rest move randomly (e.g., in a random dot kinematogram testing sensitivity to the direction of global motion), adults treated for congenital cataract have significant deficits
         • This pattern supports the hypothesis that some aspects of sensitivity to global motion depend on postnatal experience, as does visual acuity, but that the timing of the needed experience varies
         • Biological motion
           • From birth, babies look longer at a pattern of dots moving like a biological organism (such as a walking hen) than a pattern with the same dots moving in random directions or inverted, or a pattern of rigid nonbiological motion
           • Both results suggest that the initial preference is based on some innate sensitivity to certain patterns of movement that are present in moving human organisms but that are not human-specific.
           • Faces
             • Within the first hour after birth, they look preferentially toward faces over other visual stimuli with the same amount of visible energy
             • especially if the face is oriented frontally with direct gaze . The preference is based only on very low spatial frequencies ) and may be mediated in part by peripheral vision
             • Newborns’ preference to look at face-like stimuli does not appear be an attraction specifically to faces but rather an attraction to stimulus properties like being top-heavy (having more elements in the top half), having congruent structure (the outer contour is widest where the internal features are also widest), and having positive polarity (black elements on a white background)
             • Regardless of the basis for the preference, however, it assures that the newborn infant is biased to attend to faces over other stimuli in the environment and will prefer to look at an upright human face rather than an inverted face because only the former has the requisite properties.
             • Newborns’ recognition of individual faces is likely to be based on scanning the external features of the face and noting something about very blurry internal features from peripheral vision
             • By 3 months, the baby has also developed the cognitive ability to average faces across presentations to form a prototype to which future encounters are compared
             • This difference for male and female faces emerges by 3 months of age but only for same-race faces, that is, faces of the type to which the baby has been exposed - biased cultural, female same race matured age
             • Perceptual narrowing
               •  babies’ face processing improves but at the same time becomes specialized for the categories of faces that are most commonly seen, namely, upright human faces matching the baby’s ethnicity.
               • perceptual narrowing – has been well documented for both species (human vs. nonhuman primate) and for ethnicity (matching that of the baby or not)
               •  end of the first year of life, biased exposure to human faces leads babies to improve their skill at individuating human faces while their skill at doing so for nonhuman faces is attenuated.
               • As with monkey faces, initially babies can discriminate as readily between other-race as own-race faces but by 9 months they fail the same tests with other-race faces
               • This happens for speech distinctions in the language the baby hears versus other languages; for human versus animal voices; and for matching talking faces to the accompanying sound track
               • The baby learns to recognize members of his/her own “tribe” and to treat members of other groups simply as “other.” In fact, by 6 months, babies match the sound of a nonnative language with an other-race face
               • Importance of Early Visual Experience for the Development of Face Processing
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       • Newborns’ vision is limited to large stimuli of high contrast in the central visual field. Nevertheless, that type of visual input is necessary for the system to be refined later for low-level visual sensitivity (acuity, contrast sensitivity, and peripheral vision), as well as for higher-level integrative perceptual processing (of global motion, global form, and facial identity)
       • In the absence of visual input, development, at least of acuity and of face processing, the only two tested longitudinally, appears to be in stasis and the input received after treatment is not sufficient to offset the delay. One reason may be the encroachment of input from other sensory modalities
       • When the deprivation is monocular rather than binocular, such encroachment may be prevented. When the perturbation is premature birth, the extra and early visual experience appears not to aid visual development
       • The implication of these findings is that any condition or treatment that blocks early visual input is to be avoided when possible
       • he evidence on perceptual narrowing indicates that early visual experience affects the tuning of every baby’s visual processing to match the characteristics of faces and speech most often experienced
       • there is reason to suspect that there are other cross-cultural differences in visual processing that arise from variations in the mother’s diet during the pregnancy and breastfeeding and in the composition of any formula
       • In summary, the newborn baby emerges from the womb able to see the stimuli right in from of him/her that are large and of high contrast: the mother’s face usually first and foremost. Her face continues to dominate the baby’s experience over the next few months, along with the faces of the father and
   • Visual attention
     • “Attention” is a broad term used to describe a complex set of processes that enables us to filter the information available to our senses, selecting some information while simultaneously ignoring or inhibiting competing information
     •  Selection enables cognitive resources to be focused on certain items or locations
     • Because of its role as a bottleneck for sensory input, attention is a candidate for targeted interventions that may mitigate the risk for adverse health outcomes and alter the trajectory of neurodevelopmental disorders. 
     • Visual attention processes are impaired in a variety of neurodevelopmental disorders including ASDs, fragile X, and attention-deficit hyperactivity disorder (ADHD)
     • Engaging visual attention may also benefit interventions designed to improve learning and memory in at-risk populations, perhaps as a result of low SES, and also relevant to education policy
     • Different forms of visual attention are differentially susceptible to environmental influence
     • Biased competition
       •  An accepted mechanistic framework for selective attention is biased competition , in which attention is a bias or a resource allocation to one of many competing stimuli
       • Common tasks
         • Stimuli that direct attention to a particular location in space are called spatial cues. The ability to overtly orient, or move the eyes, to peripheral cues develops rapidly from birth
         • Orienting to a target that subsequently appears in this cued location is facilitated, or faster, relative to a target presented in a different location. The facilitation of orienting to a previously cued location is evident by 3–4 months of age
         • he length of time between the cue and the target is critical. If the time interval is longer, on the order of 600–2000 ms, then orienting to the cued location becomes suppressed, or slower, as attention is now biased to the competing location
         • Visual search tasks, free viewing tasks, anti-saccade task, free play tasks
         • The infants visual world
           • The prowess of human vision is central to many domains of human intelligence  We discriminate thousands of individual faces, recognize thousands of object categories, and excel under challenging visual conditions
           • We can become visual experts in recognizing birds, mathematical equations, art, and more. The developmental path to these achievements is protracted with mature levels of competence not fully reached until adolescence
           • The evidence also shows marked changes in infancy in the domains of face processing and object recognition. The evidence makes clear that visual experience itself is a significant driver of these changes
           • A complete theory of learning in any domain requires an understanding of both the learning mechanisms and the experiences – the data – on which those mechanisms operate
           • Although much research is directed to determining the developing mechanisms, little has been directed to visual experience itself
           • Visual environment
             • Infant head-mounted cameras
             • Infant visual statistics
               • Visual attention
           • Infant face perception
             • Object perception
     • Posner and Petersen’s classic model
       • Posner and Petersen’s classic model  describes three attention systems: alerting, orienting, and executive attention
       •  Alerting refers to a state of heightened arousal or readiness in response to the abrupt onset of an external stimulus. 
       • Orienting refers to the shifting of attention to an item or location in the environment, either overtly (with an eye or head movement) or covertly (without a physical movement)
       • Executive attention refers to processes that resolve competition among multiple stimuli, and includes switching, inhibition, and control processes
       • Colombo (Reference Colombo2001) divided Posner and Petersen’s orienting process into two distinct functions: spatial attention and object-based attention.
       •  Spatial attention involves directing attention to a particular location in space and enhances processing of information presented at the attended location. Object-based attention involves directing attention to particular objects or features of objects 
       • Measuring Infant Attention
         • The speed with which an infant habituates to a particular stimulus is thought to reflect the efficiency of the infant’s information processing, as disengagement from the stimulus suggests that the infant has fully processed it and committed it to memory
         • Continuously sampled eye movements can be separated into two components: saccades and fixations
         • The duration of fixations is typically associated with cognitive processes such as attention, information processing, and memory encoding, similar to looking time. 
         • Looking-time measure
           • Looking-time measures: In the past, researchers were limited to measuring coarse aspects of infants’ looking behavior – evaluating the direction of the eyes (and head) to determine whether and when infants looked at a particular image, object, or person - habituation vs dehabituation
           • The speed with which an infant habituates to a particular stimulus is thought to reflect the efficiency of the infant’s information processing, as disengagement from the stimulus suggests that the infant has fully processed it and committed it to memory
           • Infants’ sensitivity to differences between visual events can also be measured using preferential looking (i.e., if infants prefer one display to another, then they have necessarily detected a difference between the two displays) and violation of expectation paradigms.
           •  The preferential looking method takes advantage of infants’ spontaneous preferences; it does not require training -
           • In violation of expectation paradigms, infants look longer at events that are impossible or inconsistent with their prior expectations (due to “core knowledge” about how the world works)
           • n sum, looking times have historically been used to consider attention development, but indeed reflect several processes in infancy.
         • Eye-tracking
           • Eye trackers are advanced physiological measuring systems that estimate the point of gaze and motion of the eye relative to the head, allowing researchers to record exactly where participants look on a stimulus display
           • First, it is noninvasive and simple to use with infant participants, and is able to tolerate head and body movements with minimal data loss.
           •  Second, eye tracking offers substantial increases in accuracy and precision over traditional video recording, as looking behavior is sampled at a faster rate with higher spatial resolution
           • . Third, eye tracking provides real-time gaze data, affording the experimenter greater control, and removes the need for offline human coding, which is time consuming and less precise
         • Heart rate
           • The development of sustained attention has been examined using heart-rate markers in young infants as a physiological index of attentional engagement during periods of looking
           • Specifically, periods of increased sustained attention (i.e., marked by resistance to distraction, slower and less accurate shifts away from the attended stimulus) are accompanied by decreased heart rate
           • Heart-rate deceleration during sustained attention increases from 3 to 6 months, along with some developing visual processing measures such as the time required for infants to acquire familiarity with stimulus characteristics
         • EEG
           • The introduction of novel neuroimaging tools and statistical methods has provided some precision to the study of the neural architecture underlying attention development. Electroencephalography (EEG) methods have been used to study the temporal dynamics of neural signals relevant to visual attention orienting. 
           • EEG is a noninvasive, painless method for recording the electrical activity of the human brain from the surface of the scalp
           • The main advantage of EEG is its high temporal resolution; changes in the brain’s neural activation can be measured with millisecond precision as they unfold over time. However, its spatial resolution is relatively poor
           • Event-related potentials (ERPs) can be obtained from continuous EEG recordings by averaging segments that are “time locked” to a discrete stimulus or event 
     • Interacts
       •  Vision and Eye-Movement Control -  first year of life, basic features of the visual system such as acuity, binocular disparity, and oculomotor control undergo significant development, meaning that an infant’s visual processing differs from an adult’s in a number of fundamental ways
       • Comparing infants’ spontaneous eye-movement patterns over the first few months of life reveals that fixations are initially longer and more concentrated, and become more distributed and controlled by 3–4 months
       • Body Kinematics and Posture - Overt attention, relies on the physical abilities involved in holding one’s head upright, making effortful and voluntary head turns, and voluntarily controlling eye movements
       • Attention and Learning/Memory - Studies of infant looking behavior indicate that the way infants distribute their attention to a stimulus can have critical consequences for learning  - Studies have shown that orienting attention with spatial cues may enhance infants’ processing and memory for events at the cued location
       •  Joint Attention, Social Development, and Decision Making - Human adults orient automatically to shifts in others’ eye gaze, and the ability to follow gaze is a critical component of many aspects of social interaction, such as joint attention, imitation, communication, and coordinated action
       • Culture
         • Infant visual attention development is an early and critical means of information gathering and learning with long-term impact on subsequent development.
         • maternal depression is associated with stronger alerting responses to external stimuli (e.g., a bell, rattle, or light) in newborns as well as higher levels of the adrenocorticotropic hormone (ACTH), which regulates the production of the stress hormone cortisol
         • Children of depressed mothers demonstrate attentional deficits and impaired cognitive performance
         • Are Infant Attention Mechanisms Culturally Specific or Universal? -  frequent experience with own-race faces may elicit increased selective attention engagement, which has been shown to enhance the quality of early vision, contrast sensitivity, acuity, and perceptual processing of selected information
         • Infant Attention and Socioeconomic Status - These data suggest that inhibitory attention may compensate for the impact of SES on memory.
         • Infant Attention and Preterm Birth - observed that infants born preterm with very low birth weight (<1750 g) had longer look durations, slower shift rates, more off-task behavior, and lower attention to novelty than infants born full term

4. Infant memory

   • The lack of memory for our infancy and early childhood is often referred to as childhood amnesia. Although the boundary of childhood amnesia is lower in children and adolescents than it is in adults
   • These age-related decreases in the requisite specificity of effective retrieval cues increases the probability that older infants will retrieve and express their memories in a wider range of situations. 
   • This age-related increase in representational flexibility allows older infants and young children to take their memories with them
   • Child amnesia
     • The phenomenon of childhood amnesia raises important questions about memory development in particular and cognitive development in general
     • In short, the phenomenon of childhood amnesia raises important questions about if and how infants and young children use their prior experiences to guide their future behavior during the period of early development and beyond.
     • Freud’s views of childhood amnesia were guided by his clinical practice and were retrospective in nature; he drew conclusions about the source and timing of childhood amnesia by asking adults to recall their early experiences in the context of therapy
     • In contrast to Freud, our approach, and that of many of our colleagues, has been prospective in nature, tracing changes in memory that unfold as a function of age and experience during the period of infancy and early childhood.
     • Empirical methods
       • despite the procedural differences in the VRM, mobile conjugate reinforcement, operant train, and deferred imitation paradigms, the data they yield are remarkably similar
       • VRM
         • Visual Recognition Memory -infants form internal representations of stimuli that they attend to; with repeated exposure to a particular stimulus, the internal representation becomes more complete and the infant then turns his or her attention to novel stimuli in the environment
         •  In the VRM paradigm, infants are given the opportunity to view a stimulus and, following a delay, they are presented with that original stimulus and a novel one. 
         • The infant’s visual behavior (looking time) toward the novel stimulus relative to the familiar stimulus is then compared
         • infer that the infant remembers the familiar stimulus if he or she looks significantly longer at the novel one during the test - Longer looking toward the familiar stimulus has also been used as an index of memory articularly if the participants are extremely young
         • Across the infancy period, longer looking times are also associated with incomplete or partial encoding of the stimulus in the first place 
       • Mobile conjugate reinforcement paradigm
         • mobile conjugate reinforcement paradigm, 2- to 6-month-old infants learn to kick their feet to produce movement in an overhead crib mobile. 
         • In a procedurally identical task, 6- to 18-month-old infants learn to push a lever to make a toy train move around a track
         • In both the mobile and the train task, researchers measure the infant’s baseline response rate during a period of nonreinforcement at the outset of the first session and they measure retention during a period of nonreinforcement at the outset of a test session conducted days, weeks, or months after the conclusion of training.
         • Because the learning and memory performance of 6-month-old infants is identical in the mobile and the train task, combining the findings from both have provided the opportunity to trace age-related changes in memory processing across the first 18 months of life
       • Deferred Imitation Paradigm
         • In the deferred imitation paradigm, an experimenter models a series of actions with objects and then tests the infant’s ability to reproduce those actions either immediately or after a delay of days, weeks, or months
       • Implications
         • The majority of studies examining early memory development assess infants in an ideal learning environment. 
         • Testing is typically scheduled at a time of day that the parent has identified as an alert/awake period, and the to-be-remembered information is presented with minimal distractions at encoding and test
         • Measuring performance in these ideal conditions provides the foundations for understanding the ways in which learning and memory occurs, or fails to occur, in more complex environments. 
         • A number of attentional, memory, language, and social factors undoubtedly contribute to this transfer deficit - translate research into early educational and health policy and practice
         • From a memory perspective, one of the key constraints on transferring knowledge from these information sources is the lack of representational flexibility during infancy and early childhood. 
         • The mismatch between a two-dimensional information source at encoding and a three-dimensional object at test, or vice versa, constrains learning from media sources during the first years of life
         •  if we apply the basic principles of memory development from Table 12.1 to situations when knowledge acquisition or retrieval appears to fail, we can scaffold children’s experiences so that they benefit from a wider range of learning resources
         • Future directions
           • despite the highly consistent pattern of results outlined in Table 12.1, it is important to acknowledge that much of the research on infant memory development has been derived from WEIRD) participants
           • As we begin to investigate cross-cultural differences in infant memory, we should be mindful that a cross-cultural approach to research could trip us up if we are not careful.
           • ensure that the stimuli (e.g., faces, puppets, unfamiliar objects) and the environment (e.g., home, unfamiliar lab) are designed with culture in mind, allowing us to capture an infant’s skills and interests irrespective of the experiences
           • confirm (or refute) the universality of the basic principles of memory development -, in our view, this approach runs the risk of creating deficit models by highlighting how well  one cultural group performs on a specific memory task relative to another without consideration for the specific mechanisms involve
           • work more closely with families who experience greater connections to their physical environment, or who provide children with extended and multigenerational social networks early in development.
   • Age
     • (1) older infants encode information faster than younger infants,
     •  (2) older infants remember information longer than younger infants, and 
     • (3) older infants exploit a wider range of retrieval cues than do younger infants
     •  infants mature and gain more experience, their ability to encode and retain information increases. 
     • These basic age-related changes in encoding and retention have been documented using each of the three major infant memory paradigms and reflect highly replicable developmental processes
     • age-related changes in representational flexibility, or the ability to retrieve and use memories in novel situations, also increases the probability that a given memory will be retrieved, used, strengthened, and retained
     • Despite the highly specific nature of memory retrieval by younger infants, older infants and young children gradually escape the shackles of encoding specificity, retrieving their memories in new contexts or when confronted with new stimuli
     • Memory reactivation
       • Although forgetting occurs rapidly during the infancy period, researchers have also shown that apparently forgotten memories can be retrieved and expressed given the appropriate circumstances
       • in the absence of the reminder treatment, infants exhibited no retention whatsoever after either delay. Infants who received the brief reminder, on the other hand, performed at a level that was equivalent to that seen at the conclusion of training 2 or 4 weeks earlier
       • In addition, the rate of forgetting of the reactivated memory was equivalent to the rate of forgetting of the original memory.
       • Finally, effective reminders must be virtually identical to stimuli or contexts that were part of the original learning episode
       • Language
         • n additional to physical cues, verbal cues also play a pervasive role in memory retrieval by human adults
         • once we can store and retrieve information through language we are no longer bound by the conditions under which the information was originally learned; 
         • instead, we can take our memories with us, augmenting them with new information that we encounter along the way
         • At all three ages, participants in the control condition exhibited no retention, looking equally at the novel and the familiar cartoon face during the test. 
         • In contrast, participants who received the verbal reminder exhibited excellent retention, looking longer at the novel cartoon face during the test
         • Taken together, both retrospective studies with adults and prospective studies with children suggest that language acquisition plays an important role in the decline of the dense amnesia we experience for events that occurred during infancy and early childhood.
         • a major developmental milestone, increasing the probability that a memory will be retrieved and expressed after a delay. In fact, several lines of evidence now suggest that the early dense amnesia that we experience for events that we experienced prior to the age of 2 or 3 is due, at least in part, to a difficulty in gaining verbal access to memories that were encoded largely without language
         • Brain Maturation
           • The first years of life mark a time of rapid growth in the overall size, structure, and complexity of the human brain  and brain maturation undoubtedly contributes to the age-related changes in infant memory performance
           • Surprisingly, perhaps, a direct link between brain maturation and memory development has yet to be established. 
           • Brain maturation is not a linear process and different areas of the brain mature at different rates, with motor and sensory areas maturing early, and higher-order association areas continuing to mature well into early adulthood
           • Research with nonhuman primates suggests that although the major structures of the hippocampus are present early, considerable changes occur to structure and function of the hippocampus in the first 2 years
           • Because the formation of new declarative memories in adults is dependent on the hippocampus and surrounding cortices, and that the hippocampus is thought to develop late in ontogeny, it has been argued that declarative memory should also develop late and should coincide with the maturation of the hippocampus
           • Given that infants cannot verbally declare whether they experience conscious recollection, it is difficult to directly investigate the emergence of two, separate memory systems during the infancy period
           • despite the potential to map age-related changes in memory processing to the maturation of specific brain structures that support memory processing in adults, research with infants has shown that there is not a sudden shift from one memory system to another
           • Individual differences
             • Individual differences in the experiences that infants encounter in their broader daily lives, such as the opportunity to sleep, also impact memory performance. 
             • A growing body of research shows that the opportunity for a well-timed nap plays a role in memory consolidation, supporting both retention and the generalization of memory
             •  in a test of deferred imitation, only 6- and 12-month-old infants who had a nap in the 4 hours after learning showed the ability to reproduce the demonstrated actions 4 or 24 hours later
             • The ability to remember and flexibly apply memory in new situations reflects, at least in part, the richness of the encoding situation that the infant experiences
             • Memory performance is further facilitated when the learning occurs in multiple contexts , when there are opportunities to practice the target actions during encoding
             • differences in the speed at which individual infants process information, but also where and how they direct their attention that will influence what information is later available for retrieva
             • Individual differences in the experiences that infants encounter in their broader daily lives, such as the opportunity to sleep, also impact memory performance. A growing body of research shows that the opportunity for a well-timed nap plays a role in memory consolidation
         • Culture
           • Infants who are growing up in a bilingual home also exhibit an advantage on tests of representational flexibility, 
           • which may reflect enhanced attentional skills or the richer networks of knowledge that may come from exposure to two languages
           • The chances of an event becoming part of our verbally accessible personal history increases if the original experience is better understood
           • cultural differences in the value placed on engaging with the past and in the richness of the narrative input that children receive has also been linked to individual differences in the age and content of early personal memories

5. Infant physical knowledge

   • Physical reasoning is the ability to go beyond the information in the immediate perceptual array. 
   • For example, if I were to dangle my keys in front of me with the intention of letting go of them, everyone would predict that the moment I let go of the keys, they will fall towards the ground
   • demonstrate that people share the same basic ideas about how objects behave and interact. 
   • These expectations may be universal across all humans, and they may even be shared by some other species
   • even though most people can effortlessly draw similar predictions about these events, we have yet to build a computer that can rival the physical reasoning abilities of a typically developing 1-year-old infant
   • one way to resolve some of the mysteries about physical reasoning is to look at the origins of the abilities and how they change over time
   • Infant physical knowledge
     • The first challenge to understanding the development of physical reasoning is to figure out a way to ask preverbal infants what they know. 
     • One method that has been developed over the past 30 years is looking-time tasks
     • The dependent measure is the duration of an infant’s looks at the events on stage across trials. To capture the looking duration there is a small video camera beneath the stage floor videotaping the infant’s face when the curtain is up.
     • research using looking-time paradigms has revealed that infants have sophisticated expectations about how objects behave and interact.
     • A full account of physical knowledge will need to consider the interaction between cognitive, cultural, and motoric influences.
     • Violation of expectation paradigm
       • Habituation
         • The decline in looking over repeated trials is called habituation.
         •  Habituation trials are designed to teach infants the contingency between their looking away and the trial ending, as well as to familiarize them to the objects in the events.
         • After the habituation trials, infants were shown two types of test trials that alternated. In the expected test trials, a second barrier wall was introduced to the middle of the display.
         • The unexpected test trial was identical except that, when the screen was removed, the ball was against the far barrier wall
         • The results showed that infants looked significantly longer at the unexpected outcome revealing that infants expected the ball to be stopped by the barrier and looked longer at events that violated this expectation.
     • Core knowledge
       • particular, core knowledge abilities are evident early in development and they are used continuously throughout life.
       • The abilities are universal across human cultures and shared among a variety of other species. 
       • A well-studied example of a core knowledge system is the ability to discriminate quantities. This system is called the approximate num- ber system - The ability does not require counting; it is dependent on the ratio between the compared amounts. It does not require formal schooling:
       • The findings from looking-time experiments are interpreted as evidence that infants have core knowledge about objects. 
       • More specifically, infants expect objects to be continuous (e.g., they do not blink in and out of existence) and solid (e.g., two objects cannot occupy the same space at the same time).
       •  continuity and solidity are primitive and leave many aspects of object knowledge undefined. What changes over the course of development is that, through an infant’s experience interacting with the environment, these initial concepts are elaborated and refined.
       • The picture that is emerg- ing is that infants have core principles for substances that are distinct from their expectations about objects.
       • Object knowledge
         • Situations where knowledge develops through experience, but without instruction, tend to involve a process of continuity and elaboration. 
         • Therefore, studies of the origins and early development of physi- cal reasoning abilities can lend insights to the mature ability
         • experience - Another factor that interacts with the development of object knowledge is individual differences in postural milestones like sitting, crawling, and walk- ing.
         • Together, these findings are important because they capture the interplay between two developmental trajectories.
         • One is the core knowledge of con tinuity and solidity that is evident early and does not rely on experience. 
         • The other is a more protracted, experience-based trajectory that is characterized by identifying variables that allow infants to elaborate the initial concepts and become more precise.
         • Together, looking-time paradigms provide considerable evidence that a 2-month-old and an adult perceive objects in fundamentally similar ways.
       • Support
         • A second example of how physical knowledge interacts with other cognitive systems comes from studies on how infants allocate their attention to specific aspects of their environment. 
         • For example, infants who saw a solidity or no-contact support violation (similar to those described earlier) attend to that object more closely in subsequent interactions and learned to associate a novel sound with the object.
         • In contrast, when the same teaching event was coupled with expected solidity or support events, infants failed to learn this new sound property
         • That is, infants who saw violations spent more time interacting with the object involved, compared to a distractor object.
         • Containment
           • Is it possible that language specifies the spatial category boundaries, or do infants have expectations about spatial categories prior to language?
           • Casasola and Cohen (2002) revealed that 10-month-old infants have expecta- tions about containment and support prior to language production.
           • indicate that the process that governs learning word meanings has a developmental trajectory where preverbal infants are sensitive to nonnative distinc- tions. 
           • Spatial language learning seems to develop by linking linguistic forms to universal, preexisting concepts.
           • Substances
             • These reactions to spills are the result of understanding that objects and liquids have different physical properties and therefore behave differently.
             • but when do we develop the expectation that liquids deform to fill the space? 
             • This ontological categorical distinction has captivated linguists who trace cross-linguistic differences in count/mass nouns
             • growing interest in looking at the origins and develop- ment of knowledge about substances and how it compares to the representa- tions that guide expectations about objects
             • Early evidence suggested that the answer was no: infants did not have principled expectations for substances
             • as evidence that infants have principled expectations for objects but not for substances
             • Together, these findings provide evidence that expectations about substances emerge early and these inferences are based on little or no experi- ence.
             • Implications
               • It would be fascinating to know whether there is converg- ing evidence for infants’ habituation at the neural level indicated by changes in blood flow due to functional activation or changes in electrophysiological response over time.
               • reasoning about objects and reasoning about substances, but neuroscience could offer clues into how distinct these processes are and whether they diverge over the course of development - brain regions
               • The lack of variance in physical reasoning abilities across ontogeny and phylogeny suggests that there may be little variance across culture in these abilities as well.
               • However, languages vary in how they describe space - developmental changes for a variety of languages and spatial categories.
               • argued that core concepts critical to early physical reasoning – such as object and substance knowledge – are likely a part of our evolutionary endowment.
               • language may capitalize on preexisting spatial concepts and change the way that adults perceive spatial events - postural milestones like the onset of sitting, crawling, and walking can influ- ence how infants interact with objects in their environment.
               • This example highlights how parents or older peers can scaffold infants’ interaction with objects, giving them the opportunity to consider new variables sooner.

6. Early Knowledge About Space and Quantity

   • Over the past decades, we have learned a great deal about what infants bring to the task of mastering space and quantity, and what they subsequently add to these starting points
   • The accumulating findings are richly descriptive, and they are beginning to illuminate long-standing questions concerning the origins of knowledge in these domains
   • Broadly speaking, there have been two contending theoretical approaches. 
   • The core knowledge view claims that infants are born with representationally specific processing modules tuned to picking up the geometry of space (the geometric module), forming representations of objects (continuity, cohesion, contact, tracking small sets), and assessing the number of objects
   • In this way of thinking, subsequent developmental change comes mainly from augmentation of the power and scope of these innate modules, as children acquire language and other forms of symbolic processing
   • Policy implications are thus unclear for typically developing babies at present.
   •  Given that children and adults eventually show important individual differences in all three domains, whether there are environments or types of interaction that could lift trajectories early needs a more careful look.
   • Infant spatial knowledge
     • Broadly speaking, there have been two contending theoretical approaches. 
     • The core knowledge view claims that infants are born with representationally specific processing modules tuned to picking up the geometry of space (the geometric module), forming repre- sentations of objects (continuity, cohesion, contact, tracking small sets), and assessing the number of objects
     • There are two psychologically and neurally separable ways of acting in space: navigation and object manipula- tion. They have different adaptive functions and evolutionary histories,
     • Crawling and (even more) walking are crucial transitions, because we know that infants who are passively transported experience very different statistics of optic flow and motion
     • Seeing distal landmarks and realizing that can aid in navigation is a vital part of constructing an allocentric spatial framework.
     • Navigation
       • wayfinding. Navigation typically occurs across environmental scale, i.e., spaces in which movement creates distinctively differ- ent views of each local area, and not all objects and landmarks are intervis- ible.
       • Inertial information, also called path integration, refers to information derived from kinesthetic, vestibu- lar, and visual flow information regarding direction and distance of motion.
       • It supports representation of the shape of a path and the location of points along it from the current position, e.g., pointing back to a starting point.
       • Allocentric information refers to information derived from encoding direction and distance of objects in the environment from stable environmental features, including boundaries and landmarks.
       • Encoding of inertial and allocentric information is the product of the work of a dizzying array of specialized cells, including place cells, head direction cells, grid cells, boundary cells, object vector cells and more
       • Head direction cells predate movement and even eye opening in baby rats, but they seem to require input from vision and motion to stabilize - place cells
       • Object manipulation
         • Object manipulation contrasts with navigation in species specificity and in scale of operation.
         • a distinctive skill of the human species is an ability to represent and transform the shapes of objects. We can grasp objects physically and manipulate them based on their shape, modifying that shape to our purposes.
         • purposes. In planning for tool use, we may generate mental images of two-dimensional shapes or three-dimensional objects, and transform them in various ways - helps prediction
         • Manual interactions with objects are built on a neural substrate involved with allowing effective actions in the world, which consists of two separate but related processing streams - what vs where ventral vs dorsal 
         • Infant looking-time studies to explore the early roots of MR are beginning to suggest that manual experience with objects that can be rotated lays the groundwork for mature MR as it appears in traditional judgment tasks.
         • In short, MR seems to leverage the systems involved in motor planning and execution, more strongly in children well into elementary school than in adults
     • Infant number knowledge
       • of evidence that nonhuman animals have impressive abilities to estimate the quantity of both small and large numbers of objects, as well as of other quantitative dimensions such as volume
       • indicated that infants were also sensitive to larger numbers that cannot be based on object tracking, and that must tap a separate system, called the approximate number system (ANS) by core knowledge theorists
       • The core knowledge view is that the object tracking system and the ANS jointly constitute the two innate modules that underlie the subsequent acquisition of formal mathematics, with the ANS influencing mathematical achievement
       • neoconstructivist -  infants’ early sensitivity is to magnitude of various kinds, including not only the number of discrete objects (i.e., the integer system), but also continuous quantitative dimensions such as size, area, contour length, volume, time, and
       • Importantly, number and the various quantitative dimensions are typically correlated with each other in the real world. For example, having more cookies generally implies having more volume of cookie, as well as more area,
       • made the point that infant number studies had not been well controlled for quantitative dimensions other than number.
       • Untangling correlated quantitative dimensions seems to be a special case of statistical learning, as studied in other domains but knowing the input statistics would be helpful for experi- mentation and modeling.
       • Neural basis
         • Research on the neural bases of quantity and number reveals that adults show substantial overlap in the brain areas engaged in pro- cessing nonsymbolic magnitude, nonsymbolic number, and symbolic number, suggesting commonality
         • although there are also some brain areas specific to nonsymbolic and symbolic number
         • this pattern of overlapping activation extends to mental rotation
         • the intraparietal sulcus (IPS) may be a “spatial hub,” helping the navigation system to encode spatial direc- tion and relate egocentric to allocentric coordinates
         • evidence that number-relevant input affects children’s mathematical development in the pre- school years, and even after formal schooling starts,
       • Core knowledge
         • core knowledge theorists (and some others) typi- cally see such data as revealing the basic design of the human mind, what babies would tell us if only they could speak.
         • The core-knowledge and the neoconstructivist views agree that spatial and mathematical development are far from complete by the end of infancy.
         • core knowledge approach, language and other symbols play a pivotal role - neo- constructivist theories, language and other symbols are important, but they are only one among several forces propelling development.
         • Geometric module
           • As in the standard model, inertial informa- tion is important, but the only kind of allocentric information comes from the shape of enclosing spaces, i.e., “geometry.”
           • This model of mature functioning is linked to the postulation of an innate geometric module, a central plank in the core knowledge position. 
           • Surprisingly, they used the geometry but failed to use the features in search, i.e., they went equally often to the target and to the diagonally opposite corner. This pattern led to the idea of an encapsulated geometric module
           • the shift occurred between the ages of 5 and 6 years, and argued that it was due to spatial language, based on a correlation between children’s accurate produc- tion of the words “left” and “right” and success in using features to search.
           • The failure of toddlers to use features is not always observed, however.
           • In sum, language is one of several candidate factors for explaining the developmental transition in a very par- ticular environment, namely the very small room.
           • Piaget
             • An older proposal regarding the mature spatial system came from Piaget, who wrote about it as “projective” and “Euclidean” 
             • and characterized infants as “topological” and “egocentric,” with a shift from egocentric to allocentric and from topological to projective Euclidean.
             • Research based on this model used techniques such as the A-not-B search error that Piaget originally used to investigate the development of the object concept, and studies in which investigators rotate babies by 180 degrees
             • In the rotation para- digm, it turned out that even babies of 6 months or so succeeded when there were very salient visual landmarks
             • Even 4-month-olds expect that objects will occur at allocentrically defined locations following rotation when given prior experience with passive motion
             • Piagetian tradition largely supports the emerging view, using the inertial-allocentric integration framework,
             •  that infants are moving towards a mature system in which various coexisting sys- tems are both used, in a fashion paced by growth and experience.
           • Culture
             • Although cultures differ in whether they swaddle infants, encourage early sitting and walking, or allow toddlers to roam widely, these differences likely affect the pace but not the outcome of development.
             • The requisite experience is inevitably encountered sooner or later, probably with no need for special enrichment.
             • considerable individual variation - we do not know how early individual differences arise and become stable.
             • In these cases, babies will likely benefit from adaptations that allow them as much free- dom to explore as possible
             • Cultures differ dramatically in their number systems, with some languages pro- viding only a rudimentary list of count words and no formal mathematical   instruction, 
             • other cultures offering more complex but still cumbersome sys- tems, and complex societies offering well-developed and culturally valued ways to calculate
             • Western   industrialized countries, and especially in middle- and high-socioeconomic sta- tus groups, adults may use number words and engage in number activities with infants, at least starting in the second year
   • Neoconstructivism
     • By contrast, a neoconstructivist view pro- poses that the newborn human mind is broadly prepared to acquire knowl- edge from interaction with the structure of the expectable environment
     • Representational preprogramming is not essential, because infants inevitably encounter crucial information in a world constrained by the laws of physics. 
     • The developmental unfolding of sensory, motor, and brain maturation creates a sequence of relevant experiences that lead to typical development.
     • neoconstructivist investiga- tors mostly regard looking time as reflecting weak and inchoate tendencies or perceptual biases, rather than knowledge that can support actions, judgments, and decisions
     • It considers evidence from looking-time studies as providing information regarding possible early starting points (rather than full-blown competencies).
     • Other factors are also vital, such as increasing integration of cue systems (adaptive combina- tion;) and environmental input, nonlinguis- tic as well as linguistic.

7. Action in development

   • Infant motor skill acquisition is so rapid and dramatic that a century of researchers – and eons of parents – have marveled at the scope of developmental change
   •  At birth, infants are essentially prisoners of gravity, unable to lift their heads from their caregivers’ chest. But by 2 years of age, infants can “pluck a pellet with fine pincer prehension”
   • This remarkable transformation in action characterizes the development of basic motor skills – posture for supporting the body against gravitational and inertial forces, manual skills for interacting with objects and surfaces
   • and locomotion for moving the body through the environment
   • Infant motor development
     • After birth, gravity poses a continual challenge as infants acquire increasingly erect postures over an increasingly small base of support. Generally, posture develops top down, from head to toe
     • Newborns struggle to hold their heads upright, new sitters work to control the segments of the spine, and new walkers cope with balance at the hip, knee, and ankle joints.
     • Keeping balance, however, is rarely an end unto itself. Rather, postural con- trol provides the foundation for other actions
     • posture must be sufficiently developed to anticipate  and control for the potential loss of equilibrium. Postural control must pre- cede the development of other motor actions and the opportunities they pro- vide
     • Manual actions appear long before birth. Fetuses flex and extend their arms, wiggle their fingers, and clench their fists; they grasp the umbilical cord, rub the wall of the uterus, and bring hand to mouth to suck their thumb
     • plasticity, variability in and among infants, and flexibility
     • intervention: Start early. More is better. Function over form. Adapt to change. And learn by doing.
     • Locomotion
       • Locomotor movements also begin before birth with fetal leg kicks
       • Leg movements continue after birth, but newborns’ kicking and stepping doesn’t take them anywhere because they cannot keep balance or support their body weight.
       • Locomotion – moving the whole body from one location to another – allows infants to move away from their caregivers or to move closer to them. 
       • They can engage with distant objects, visit familiar or new places, and interact with the structural layout of the environment (e.g., crawl up stairs or under chairs).
       • Whereas postural and manual actions facilitate visual and manual exploration of the surrounding environment and objects, locomotor actions involve whole- body exploration of surfaces and places
       • Infants’ locomotor skill is usually tested on a motorized treadmill or while infants crawl or walk along straight paths over open, uniform ground  But functional locomotion occurs in a cluttered environment with variations in the terrain.
       • Infant manual action
         • objects differ in orientation, shape, and size, infants must use visual information to prospectively modify their grip. Infants use visual information about object properties to appropriately orient their hands to grasp horizon- tal and vertical rods
     • Infant posture
       • With increased postural control and strength, true mobility generally progresses from more to fewer body parts on the ground 
       • – first pivoting and belly crawling with the abdomen on the ground, then crawling on hands and knees or bum shuffling in a sitting position, then cruising while holding furniture for support, and finally walking independently.
       • The general pattern is from less to more upright postures, but sitting, hands–knees crawling, pulling to stand, standing, and cruising sideways along furniture appear in a variety of orders across infants
       • Motor milestones
         • Milestones are the legacy of the early pioneers in infant motor development - Their selection of skills was largely arbitrary
         • The milestone charts in modern-day developmental textbooks, parenting guides, and the pediatrician’s office perpetuate the distorted legacy of the early pioneers.
         • Although their intention was to study the shape of behavior in real time and over development , the surviving charts emphasize age-related stages over developmental process.
         • too much “attention has been centered on determining when particular characteristics appear without proper analysis as to the process or the means whereby they are acquired”
         • data from most cultures are missing from the milestone charts. Babies from around the world are commonly compared to Western age-norms for items selected by Western researchers nearly a century ago
         • Indeed, infants with more motivation to move (as indexed by higher spontaneous activity levels, more persistence, and fewer requirements for social encouragement) achieve their milestones at earlier ages than less motivated
         • Plasticity
           • Rather than a universal, obliga- tory series of ages and stages, plasticity is intrinsic to motor skill acquisition. 
           •  The skills infants acquire, the ages they first appear, and their subsequent developmental trajectories are highly responsive to cultural and historical differences in childrearing practices and infants’ everyday experiences.
           • Rather than being rigid and fixed, flexibility is fundamental for motor behavior. Variety in motor actions is often a choice, not a by-product of poor motor control.
           • Motor actions must be flexible because infants’ bodies and environments are continually chang- ing. Thus, infants modify ongoing actions, select different actions
           • seemingly mundane activities such as how caregivers hold, carry, bathe, dress, and position their infants for sleeping affect the form and timing of motor development.
           • Deliberate exercise, restraint, and habitual practice do likewise, but the items and age bands on normative milestone charts such as the WHO standards do not reflect the global diversity
         • Individual differences
           • on years of habitual practice in childhood – the deep squat (used in many cultures to rest or defecate), deep kneel (prayer position), cross-legged sit,
           • Movements depend on biomechanics – muscle activations, body position, and the environment. Such intrinsic and extrinsic factors vary from moment to moment, so movements, like snowflakes, are never exactly the same
           • Moreover, infants’ neuromuscular system is highly vari- able. As a consequence of variable biomechanical factors and a noisy con- trol system, intraindividual variability is endemic in infant motor behavior
           • In situations where consistency is paramount, intraindividual variability typically decreases over development
           • Similarly, when the task is to reach repeatedly to a target at midline, intraindividual variability decreases and infants’ reaches become more predictable, accurate, and efficient.
           • But when analyzed up close and in detail, each infant’s developmental trajectory improves at its own rate, with its own messy progres- sions and regressions.
           • Cultural
             • Across cultures, caregivers have different expectations about the necessary input for healthy motor development. 
             •  In many cultures, caregivers handle young infants like a fragile carton of eggs by supporting infants’ heads and torsos against gravity.
             • But in some African and Caribbean cultures, caregivers expect infants to withstand gravity on their own. Caregivers pick up infants by an arm, suspend them by their ankles or head, and toss them in the air and catch them
             • Moving infants slowly and   gently is the norm in some cultures, but in others, intense vestibular stimula- tion is common.
             • Childrearing practices can also delay infants’ motor development by restrict- ing infants’ movements.
             • The result of all the shaking, jouncing, tossing, and exercise is that infants hold their heads up, sit, walk, and run at earlier ages than expected by the WHO standards
             • Within a culture, historical changes in childrearing practices can affect motor development.
             • Implications
               • Gesell and McGraw also viewed motor development as a window into neu- ral function. But the neural underpinnings of movement cannot be directly observed.
               • Like Gesell’s original schedules, modern-day researchers and clinicians continue to use develop- mental screening tests to diagnose developmental delay and disability
               • Cultural, historical, and experimental data show that motor development is remarkably plastic and dependent on childrearing practices - self-generated expe- rience, distribution of self training & developmental timing
               • Instead, what is needed are therapeutic approaches that emphasize function over form. For basic postural, manual, and locomotor skills, therapists should aim for the “Goldilocks” amount of intraindividual variability – the “just- right” amount that allows infants to explore the problem space while allow- ing for functional outcomes
               • The bidirectional processes between behavioral flexibility and neural con- nectivity have important implications for clinical practice  - children must learn to adapt to changing environment
               • interventions should seek to replicate the varied experiences generated by healthy infants in real-world settings. Therapists and caregivers can intervene by strategically adjusting the environment to target the perceptual-motor systems that support behavioral flexibility.
               • the most effective interventions for children with disabili- ties incorporate child-initiated movement and environmental modification
           • Flexibility
             • Infants acquire new postural, manual, and locomotor skills in a body and environment that are constantly in flux. Infants can grow nearly 2 cm in a single day
             • Variations in infants’ bod- ies and environments require behavioral flexibility – the ability to tailor motor actions to changing body–environment relations
             • By the time infants can sit independently, they show impressive behavioral flexibility. Sitting infants modify their postural sway to keep balance on var- ied ground surfaces such as foam surfaces varying in compliance
             • They respond to external perturbations by showing direc- tionally specific postural responses when the floor moves unexpectedly for- ward or backward
             • Behavioral flexibility enables infants to achieve the same functional outcome using a variety of means. When there is more than one way to solve a problem, infants use a range of strategies.
             • In many cases, infants discover alternative solutions in the midst of the task despite having previously displayed successful solutions already in their repertoires.
   • Mirror neuron system & social cognition
     • The ability to understand others’ actions and intentions is at the core of human social competence. 
     • Action understanding, what it means and how it develops, has received much attention in developmental research because it is viewed as one of the most fundamental abilities in early social-cognitive development.
     • For example, there is a growing body of evidence linking early action understanding with later theory of mind - and to the development of communicative skills
     •  Increasing evidence suggests that the mirror neuron system (MNS) is a key neural correlate of action understanding. In this chapter, we discuss the role the MNS is thought to play in the development of social cognitive skills in infancy. 
     • discuss the current challenges of measuring the MNS that are unique to work with infants, what such studies have found in both typical and atypical populations, and how this work can impact our understanding of development.
     • From this body of work, we can conclude that the MNS is malleable not only in infancy but in adulthood as well. This characteristic has been taken as evidence in favor of the associative accounts for the MNS
     • Mirror neuron system
       • The MNS is a network of brain regions that are active when perform- ing an action as well as when observing others perform the same or similar actions.
       • Originally described as single neurons in nonhuman primates in area F5 of the ventral premotor cortex, 
       • the MNS is now considered to be a more extensive net- work involving parietal and premotor areas - limbic structures involved in communication and emotion
       • human MNS is considered to be a broad network of brain regions that show a mirror-like pattern of activation involving the superior parietal lobe,
       •  the inferior parietal lobe/intraparietal sulcus (IPL), superior temporal sulcus (STS), posterior middle temporal gyrus, dorsal premotor, and ventral premotor/inferior frontal gyrus (IFG)
       • Since its discovery, the MNS has been thought to support social cognition -  implicating the MNS in several neuro- logical disorders
       • Given that the abilities to understand and execute actions emerge early in development and change considerably during infancy and early childhood, examining the early development of the MNS may provide important insight into the function and significance of this system
       • ASD
         • Because of its documented and putative role in typical social devel- opment, the MNS has been investigated in individuals with developmental disabilities including autism spectrum disorders 
         • characterized by impairments in social communication combined with restrictive/repetitive behaviors and preferences, ASDs are also associated with impairments in imita- tion
         • some studies show a lack of neu- ral mirroring during action observation in ASD alongside typical activation during action execution
         • In the search for a biomarker or neurocognitive mechanism for the social commu- nicative impairments for ASDs, enthusiasm for the MNS has therefore waned.
         • Additionally, investigations of the MNS in ASD have focused on older, higher-functioning participants with average IQs, making it difficult to generalize findings across either the spectrum of impairment or across the life
         • Infants at risk for autism show differences in motor development compared to infants with typical development within the first year of life, including impaired gross and fine motor development
         • possible that any group differences in the MNS in infants with ASD could be driven by differences in motor experiences alone.
       • +
         • activation in an infant’s sensorimotor cortex while they perform an action directly matches the activation that occurs while the infant observes that same action.
         • observer. This resonant activation of the motor system enables one to under- stand the observed actions and intentions behind those actions
         • This bottom-up hypothesis fits well with many cognitive theories of action understanding including Tomasello’s emphasis on intention understanding in social cognitive development
         • when an infant perceives another’s action, the infant understands that action in terms of the outcomes it is designed to achieve, that is, an understanding of the actor’s intentions
         • the EEG mu rhythm is the measure most com- monly utilized in studies of the MNS in infants.
       • Embodied cognition
         • The theory of embodied cognition also emphasizes the importance of sensorimotor experiences in development  
         • According to the theory of embodied cognition, learning and development are supported by, and in some cases impossible without, direct sensorimo- tor interaction with the environment
         • Further, the sensorimotor experience of observing others act becomes linked to the sensorimotor experience of an infant’s own actions and in this way, others’ actions become interpretable.
         • Infant social cognition
           • these findings suggests that while mirroring mechanisms are indeed present early in development, experience plays a role in refining the system,
           • if the infant MNS reflects processes of goal interpretation or prediction, the only condition in which they would see MNS activity would be when the typi- cal grasping hand reached behind an occluder, that is, when a goal could be  inferred.
           • 14-month-olds exhibit greater mu rhythm desynchronization during dyadic, back-and-forth interactions with an experimenter as compared to nondyadic interactions.
           • evidence for the direct-matching hypothesis of the MNS. Specifically, mirroring activity is seen early in develop- ment, in response to motor activity and actions that are sometimes outside of  
           • the infant’s own repertoire, and seems to be related to understanding the goals and intentions of others’ observed behaviors.
         • Culture & experience
           • evidence for a relation between action experience and motor system activity.
           • Examining this within adults, several studies have compared mu rhythm desynchronization during observation of actions in “experts” versus “novices” for a variety of tasks or activities.
           • Examining this within adults, several studies have compared mu rhythm desynchronization during observation of actions in “experts” versus “novices” for a variety of tasks or activities.
           • They found that participants who had physical experience with the tool exhibited greater mu desynchronization during observation of tool use
           • Crawling experience (i.e., how long they had been crawling) in 14- to 16-month-old infants was related to the strength of mu rhythm desyn- chronization
           • that first-hand experience is not necessary, but that obser- vational experience may also be related to the strength of motor system activity during observation of actions.
           • Further, based on the link between experience and strength of MNS activity, one might expect to see cultural differences in MNS specific to actions that are more or less prevalent in different cultures.
           • Implications
             • Understanding the neural bases of the emergence of social cognition may have important implications for understanding, preventing, and treating  a number of disorders and problems in social communication.
             • This is particularly the case given accumulating evidence for the role of early intervention in altering trajectories for infants and young children with and at risk for social communication disorders
             • Emerging evidence sug- gests that in typically developing infants, acquiring skills (e.g., motor and action representation skills) may alter how those infants interact with the world, potentially providing scaffolding for earlier acquisition of developmental milestones
             • enhancing motor expe- rience and learning in infants may be a window into interventions for deficits in social communication.
     • EEG mu rhythm
       • The mu rhythm is an EEG oscillation in the alpha frequency range recorded over scalp areas overlying the sensorimotor cortex. 
       • Mu rhythm is typically measured within ~8–13 Hz in adults and ~6–9 Hz in infants and young chil- dren
       • When a person is at rest, neurons in the sensorimotor cortex fire in synchrony, which produces rhythmic oscilla- tory activities in the mu frequency band.
       • when a person performs an action, the firing of neurons becomes desynchronized 
       • the desynchronized neural activity leads to attenuation or reduction of the ampli- tude of the signal, which is commonly known as mu desynchronization or mu suppression
       • Mu desynchro- nization is thus measured as changes of activity relative to a resting baseline time period, and is characteristic of an active brain state and considered as an electrophysiological correlate of sensorimotor cortex activation
       • Although there has been a rapid increase in developmental research utiliz- ing mu rhythm, methodological issues hinder integration of these findings into a comprehensive theory of mu rhythm development and MNS
       • fNIRS
         • EEG mu suppression has been the most frequently used method for investigation of neural mirroring in human infants, other neuroimaging techniques have demonstrated potential in clarifying underlying structural and func- tional properties of the developing system.
         • fNIRS, which relies on differential absorption of infrared light by oxygenated and deoxygenated - hemoglobin to probe neural activation, has been used with increasing frequency to investigate action, action observation, and imitation across development.
         • One advantage to fNIRS, particularly in comparison to EEG, is increased spa- tial resolution, which allows for measuring functional activity across distinct brain regions associated with the neural mirroring network.
         • Another advantage is that the fNIRS signal is less susceptible to motion artifacts compared to other neuroimaging methods - good to measure infants
         • fMRI studies in infants are generally restricted to presentation of auditory stimuli during an infant’s natural sleep.
         • structural MRI has been used to characterize anatomical changes in the brain over the first years of life, including changes in thickness and surface area of the cortex across regions associated with neural mirroring

8. Infant Object Manipulation and Play

   • Natural and manufactured objects saturate human culture. Infants need not do much or go far to find objects of different shapes, textures, sizes, and functions throughout their environments
   • And, as they manipulate and play with objects, they learn quite a lot along the way. From the time they can swipe and grab, infants spend most of their awake hours exploring objects – moving seamlessly from object to object in short bursts of activity distributed over time
   • these bouts of object interaction allow infants to practice and refine manual skills, learn about object features and functions, and test the fit between body and environment
   • Object interactions also allow infants to extend the limits of reality. Infants can pretend that objects exist when they do not, use objects to stand for other objects, and generate unique ways to use objects beyond their intended design.
   • Indeed, to fully engage human artifact culture, infants must become proficient at using objects in twin planes of action – the real and the imagined
   • Object manipulation and play follow similar developmental paths, reciprocally influ- ence one another throughout development, involve related neural pathways, and are embedded in sociocultural practice.
   • a key aim of play research is to document how infants progress from actions based on the functions of specific toys – such as pushing buttons on a busy box – to using toys to reenact experiences in pretend stories.
   • Infant object manipulation
     • Researchers of object manipulation primarily investigate infants’ development of manual skills, emphasizing perception–action feedback loops and object affordances, with less attention to how infants embark on the imagined “as if” world
     • Our goal is to dismantle this artificial divide by showing that object manip- ulation and play are more intertwined than traditionally thought.
     • The cognitive perspective on infant play has led researchers to leverage the play context to test infant cognitive development across a range of areas.
     •  Play has become a principal way to assess other things, as has also been the case with object manipulation.
     • researchers often observe infant and child play or act out pretend stories to test causal reasoning, perspective taking, theory of mind, generic knowledge about object categories, and understanding of others’ goals and intentions
     • for many years, object manipulation was not studied as a skill in its own right, but as a means to investigate some other cognitive capac- ity.
     • infants and young children who face motor challenges - The sticky-mitten manipulation mirrors a growing trend in the pediatric rehabilitation sciences
     • Piaget
       • Research on infant object manipulation and play share a theoretical basis in the writings of Piaget, who studied object manipulation to characterize infants’ nascent knowledge about the physical world, and symbolic play to character- ize infants’ abilities to mentally represent their worlds
       • For Piaget, object manipulation was of interest less as a topic in its own right than as a means to discover what infants understand about the physi- cal environment.
       • looked to the heterogeneity and quality of infants’ actions on objects to reveal whether infants understood that objects exist indepen- dently of the self, and more generally, whether infants had developed a capac- ity for representational thinking.
       • According to Piaget, up until sensorimotor stage 4 (roughly beginning at 8 months), infants typically deploy similar routines to manipulate objects, regardless of objects’ features or properties.
       • second year – stages 5 and 6 of the sensorimotor period – Piaget noted a qualitative shift in infants’ interactions with objects. Infants could now reason fully about objects and appreciate that objects exist independently
       • Across the first 2 years, play progresses from exploration, to concrete actions on objects, to extended bouts of symbolic play that contain elaborate storylines
       • early childhood, symbolic play develops into complex role play, in line with children’s gains in narrative skills
     • Gibson and Perception–Action Theory
       • Eleanor Gibson offered an alternative view to Piaget’s theory of infant object manipulation and play, focusing primarily on how infants use action to explore and gain information from the environment
       • In the Gibsonian account, perception and action are integrally intertwined. Humans and animals perceive opportunities for action or “affordances” in the environ- ment that are scaled to their own physical characteristics and capabilities
       • Like other features of the environment, the Gibsons considered objects to be rich in information about affordances.
       • infants already possess a suite of action systems, including looking, mouthing, and manipulating, which allow them to explore, register, and use this informa- tion
       • The developmental task for young perceivers then is not to supplement or construct information about objects from impoverished stimulation as Piaget suggested, but to recruit and integrate existing action systems to differentiate the relevant affordance information.
       • Humans possess an opposable thumb, which facilitates exploratory actions such as grasping, holding, and pressing. These actions may occur either against the surface of the palm, where a power grip might be involved, or against a surface
       • Infant object exploration
         • During the second half year, as infants gain more and more con- trol of their finger, hand, and arm movements, they increasingly tailor their manual actions to the properties of the object that they are handling
         • Contrary to accounts that suggest that object manipulation and play are undifferentiated during most of the first year - infants manipulate objects in a targeted manner, closely gearing their actions to an object’s physical characteristics.
         • the motor system acts as a rate-limiting factor vis-à- vis object exploration. As new manual capabilities  come online during the first year, new opportunities arise to apply previously unavailable types of action to objects.
         • developmental changes in the manual skills that underlie haptic exploration would largely predict when sensitivity to different kinds of material properties - the role of cognitive load or complexity in early forms of skilled action becomes apparent,
         • Prospective adjustments  help ensure that once an object is contacted, subsequent manipulation will be efficient and effective. Prospective adjustments of the hand are typically evoked by visual information about an object  and thus involve a form of visuomotor coordination.
         • when reaching, infants increasingly make appropriate anticipatory adjust- ments of the hand based on an object’s orientation before the middle part of the second half year
         • these findings highlight the specificity of infants’ manual actions: Infants combine objects with surfaces selectively, taking into account the material properties of each.
         • Infant play
           • Infants’ entry into play begins with exploration. Yet, unlike the rich characterization of object manipulation described by perception–action researchers, play researchers have largely ignored the nuanced behaviors that comprise infants’ exploratory actions,
           • The general lack of attention to exploratory play reflects the favoring of symbolic play as most cognitively advanced.
           • Toward the end of the first year, infants shift from primarily exploring objects visually, orally, and manually to engaging in nonsymbolic or functional play
           • Infants begin to discover the designed features of objects, as when they press buttons on phones or turn dials on busy boxes.
           • At first, infants pri- marily direct nonsymbolic play actions to single objects, but soon relate objects to one another, for example placing objects onto or into other objects.
           • remains a curious disconnect between studies of infant object manipulation, guided by a perception–action framework, and studies of infant play, guided by a cognitive-developmental framework.
           • “object manipulation” and “toy play” offer complementary perspectives to identifying the mechanisms that underlie how infants engage with their physical environ- ments.
           • Symbolic play
             • Around the start of the second year, object play grows in abstractness as infants move from sensorimotor exploration and functional, nonsymbolic actions to displaying their first acts of symbolic or pretend play.
             • For example, infants who pretend to feed teddy trans- form their prior experiences at mealtime into an “as if” scenario  reenacting the past in a nonliteral present context.
             • Again, however, studies on symbolic play emphasize intention, rather than outcome or process, in line with the dominant cognitive foundation.
             • Infants might be credited with “symbolic play” whether or not the teacup falls over during the pour or the stir - unsuccessful attempts remain undistinguished from successful outcomes, over- looking how motor skills might contribute to implementation.
             • In symbolic play, sequenced actions that follow a logical order indicate that toddlers are laying out a pretend story not yet evident in the context-dependent, single acts of pretense seen at the start of the second year.
             • Pretend play
               • Pretend play, therefore, is quite special. It reflects the child’s understanding that actions with objects can be based on made-up situations that are separate from reality
               • simple, fleeting bouts of early pretend play at the start of the second year evolve into lengthier, elaborated play scenes from the second through  
               • third years, as infants increasingly string actions together to create play scripts, extend their play from self-directed actions to other-directed actions
               • Pretend play likewise shifts from the use of objects as designed to using objects flexibly and imaginatively.
           • Object play
           • Self
             • animals. Distancing from the self extends to everyday object manipulation, tool use, and pretend play. Changes in motor and cognitive skills enable these developments.
             • Specifically, the perception– action demands involved in directing an action toward oneself differ from those required when acting toward others.
             • play’s progression from self-to-other directed pretense exemplifies theories of cognitive decentering or distancing
             • Infants direct their first pretend acts toward the self, often simulating their own activities, such as eating, drinking, and sleeping  But several months later, infants pretend toward others, whether a care- giver, pet, or doll, with play becoming increasingly abstract and distanced from the child’s own sensorimotor actions
             • essence, infants’ actions with objects must flexibly move beyond the conventional uses of objects to identify alternative possibilities. This takes time. At first, infants rigidly adhere to the common functions
             • With development, infants grow in planning and prospective control, thereby distancing their actions in time and space - infants’ growing abilities at visual and manual integration allow them to prospectively control their actions
         • Neural
           • Researchers have long recognized that advances in object manipula- tion and play are linked to the development of the nervous system - the pyramidal/extrapyramidal tracts and the ventral and dorsal streams.
           • Geselll tied the achieve- ment of various milestones in manual and adaptive behavior, some of which also involved play with objects - to the maturation of the central nervous system
           • EEG; functional mag- netic resonance imaging, fMRI) require infants to remain relatively station- ary to guard against motion artifacts in the data.
           • Object manipulation and play, however, are inherently about movement, and certain behaviors in par- ticular, such as object banging, can be quite vigorous.
           • Newer techniques, such as functional near-infrared spectroscopy (fNIRS), may be more forgiving of infant movement than EEG and fMRI,
           • much less is known about whether such corresponding phenomena occur for domains involving eye–hand coordination and associated experiences during human infancy. Nevertheless, this is a fundamental question for the pediatric rehabil- itation sciences, where issues about timing, dosage and delivery of experience are critical for outcome
           • suggests that advances in object manipulation and some forms of object play may be associated with growth in functional connectivity between the ventral and dorsal pathways.
           • Social
             • Thus, developments in object manipulation and play cannot be divorced from social life or the home environment in which children develop.
             •  In fact, Vygotsky observed that in the context of joint activity with a caregiver, young children begin to master skills that they would be unable to perform independently.
             • experienced members of the culture bridge or scaffold young children’s skills. Over time, children internalize what they’ve learned through their interactions with caregivers
             • Scaffolding of Infant Object Manipulation, Scaffolding of Infant Play - caregivers roles have been neglected for long
             • presence of an adult during play allows infants to embellish storylines in new ways,
             • The temporal attunement of mother–infant play in real time cuts across age. Over the course of infants’ second year of life, mothers shift to more advanced forms of symbolic play in line with their infants’ growing skills
             • mothers deploy a variety of behaviors to scaffold infants’ understanding that they are merely “pretending.”
             • Culture
               • the process by which skills are socially transmitted from more to less experienced individuals may vary from culture to culture and even within a culture. 
               • Cultural norms or beliefs about infant development shape how often, for example, parents jointly manipulate objects or participate
               • In some cultures, caregivers engage in overt pedagogy, whereas in others, caregivers expect infants and young children to learn through observa- tion
               • Parents vary considerably in their perceptions of play, the value they place on play, and how often they play with their infants
               • Ni-Van caregivers displayed less visual attention to their infants’ faces than did US mothers, but greater physical touch.
               • Finally, cultures differ in the physical materials available for infant play. Infants from different cultural communities encounter and interact with different types of objects, which then affects their learning and expectations
               • cultural differences are often conflated with differences in family socioeconomic status (SES), which might also influence the materials available to infants, caregivers’ time for play and views around play,
               • Implications
                 • Interactions with objects provide opportunities for infants to learn about themselves and the world – how objects work, what can be done with objects, how to create pretend stories,
                 • Still, parents, educators, and policy makers unaware of the benefits of object manipulation and play for learning. 
                 • interventions around object manipulation and play have long been shown to foster motor, language, and cognitive development in infants.
                 • interventions aimed at promoting playful interactions between parents and toddlers during block play resulted in greater vocabulary growth in children in a treatment compared to control group of toddlers
                 • interventions aimed at promoting playful interactions between parents and toddlers during block play resulted in greater vocabulary growth in children in a treatment compared to control group of toddlers
                 • insufficient to merely educate parents on the importance of infant object manipulation and play. Rather, parents must be aware of the ingredients to productive interactions, including the value of hands-on learning
                 • education settings: choose “learning” over play due to performance pressures, an orientation that is erroneously grounded in the idea that play and learning are incompatible

9. Infant speech perception

   • Infant vocal behavior changes dramatically over the course of the first year of life, and this is considered by many to be one of the defining features of our species. At birth, human infants produce only cries, vegetative sounds, and short, quiet initial precursors to speech.
   • By the end of the first year most children can produce long sequences that include a variety of speech sounds, can coordinate their vocalizations in turn-taking patterns with other humans,
   • It appears that this process of vocal learning is the product of endog- enous exploration influenced by social input from responsive caregivers. We are beginning to gain an understanding, aided by computational modeling studies and by neuroscientific research
   • In particu- lar, there is some evidence that spontaneous activity and reinforcement-driven learning in cortical regions play a major role.
   • some sociocultural and clinical differences in vocal learning and early speech production , many aspects of the prelinguistic vocal learning process are fairly robust.
   • Interventions to increase infant vocalization rates and language learning more generally tend to focus on increasing adult caregivers’ verbal input, particularly in the form of sensitive responding to infant vocalization and other behaviors.
   • At birth, perceptual biases are in place that predispose infants to listen more attentively when they hear speech and to look toward human faces – two core communicative sensitivities
   • Prelinguistic Vocalization Types
     • the neonatal preference for the unfiltered speech heard outside the womb is equal to presentations of the filtered speech mim- icking that heard in the womb, suggesting that this preference is not entirely dependent on experience
     • These early preferences suggest that experience in utero shapes infants’ expec- tations of the auditory environment, guiding early auditory attention.
     • At birth, most infant vocalizations are limited to cries, vegetative sounds (such as burps and sucking sounds, produced as byproducts of other processes), and short, quiet sounds where there is vibration of the vocal folds but the upper vocal tract
     • Early Meaningful Speech
       • Rich social experience interacts with intrinsic neurobiological systems to scaffold perceptual abilities that support language acquisition.
       • At birth – indeed, as early as 26 weeks gestation, prior to input from developing auditory pathways – the basic neural architecture is in place for processing language.
       • Arguably, the most engaging speech for infants comes from en face interaction, providing information not just about acoustics, but also visual speech.
       • The earliest and most robust evi- dence of audiovisual (AV) speech perception comes from studies of matching -  Just as auditory phonetic speech discrimination attunes to the repertoire of the native language, so too does AV detection of the match/mismatch.
       • First, whether infants use native phonetic categories to distinguish previously heard word forms versus mispronun- ciations, independent of tying them to meaning.
       • Second, meaningful word recog- nition: recognizing the match between known words and known objects, wherein the words can be either correctly pronounced or have a (native or nonnative) pho- netic feature change.
       • studies of meaningful word learning: do infants use native phonetic/phonological categories to guide the learning of new words.
       • Development of Conversational Turn-Taking
         • Well before word production or even canonical babbling occur, infants begin to exhibit conversational turn-taking skills. From as early as 2 months, infant–adult vocal interactions tend to occur in distinct turns
         • early ages, caregivers appear to drive more of the turn-taking than infants, but over the course of the first year of life, infants are increasingly able to contribute to minimizing overlap
         • The ability of an infant and an adult to exhibit such coordination in vocal- ization timing, particularly matching the timing of pauses between the other speaker’s vocalization offset and one’s own vocalization onset, at 4 months has  
         • been shown to be correlated with later infant attachment security and cog- nitive skills at 12 months
         • Interestingly, at least one study has found that infants have increased lags in their vocal responses to caregiver vocalizations at around 9 months, when infants are on the cusp of producing first words; 
         • this may be because of the increased cognitive and motor demands incurred by the process of formulat- ing verbal responses
         •  neural activations in Broca’s area during language processing mediated the relation between adult– child conversational turns at home and children’s language skills, revealing a neural mechanism for how language skills develop in response to social lan- guage experience.
         • Mechanisms of Vocal Learning and Speech Production
           • Still unknown is exactly what are the learning mechanisms that underlie perceptual attunement to native phonetic categories. 
           • In speech, babies hear noncontinuous variation in the acoustic-phonetic properties of the sounds and syllables used in their native language.
           • Intrinsically Motivated Play, Social Input, Adult Responses as Positive Reinforcers, Adult Input as Targets for Imitation
           • Sociocultural Perspectives
             • Many babies grow up learning two or more languages from birth. 
             • While there are differences in the trajectory of perceptual attunement and eventual language learning, the course of acquisition is similar between monolingual- learning and bilingual-learning infants
             • Prior to  perceptual attunement, young bilingual-learning infants are able, just as are  monolingual-learning infants, to discriminate both native and nonnative pho- netic distinctions.
             • some studies suggest bilingual-learning infants may   go through a period, around 8–10 months of age, where they temporarily stop discriminating an infrequent phonetic contrast used in only one of their two native languages
             • bilingual infants maintain sensitivity to nonnative distinctions – those not used in either native language – for a longer period of time than their monolingual-learning peers.
             • suggest it is not an age difference in establishment of native phono- logical categories, but rather the appropriateness of the stimuli that accounts for differences observed in bilingual and monolingual infants’ learning of word–object pairs.
             • it has not yet been determined whether there are sub- stantial cultural effects on infants’ prelinguistic vocalization frequency, types, and developmental timelines.
             • Clinical perspective
               • understanding of how early perceptual attunement to different aspects of the speech signal work together to support word learning in an interac- tive process, 
               • as well as the biological mechanisms regulating this attunement, will better position us to support language acquisition in premature infants,
               • In cases of severe or profound hearing loss without amplification, infants show both delays and differences in their prelinguistic vocal development.
               • particular, while they do eventually transition from noncanonical to canonical bab- bling, they typically do so at 10 months or older, which is a considerable delay
               • retrospectively analyzed home videos of infants later diagnosed with ASD and found that most of the infants produced less canonical babbling than typically developing infants. Interestingly, two of the infants with ASD produced more canonical babble than typically developing infants;
               • thus seems that differences in preverbal infants’ speech-related vocalizations may be potential early indicators of autism risk.
               • Policy perspective
                 • Early language experience is critical for speech acquisition.  the acquisition of a language from birth is an active process;
                 • rich language experience and genetically driven developmental programs interact over the first years of life to wire up the lan- guage systems in the brain during a number of early, cascading critical periods that support later language development.
                 • support access to a rich early language environment for infants. This includes parental leave policies that allow parents to be with their children during the first year of life, and provide support for mothers suffering from depression.
                 • Successful language acqui- sition requires more than just exposure to auditory streams of speech, it  requires interaction with the caregiver. Social interactions provide visual and tactile information that support
                 • Infants born to mothers who have been diagnosed with depression show delayed tuning to native-language contrasts, which may be due to reduced interactive language input and maternal sensitivity
                 • There are a number of cases where differ- ences in early environmental exposure affect language acquisition, including infants born prematurely.
                 • several aspects of speech perceptual development, including sensitivity to the native-language rhythm and phoneme category formation, are gated by critical periods - other aspects needs experience
                 • +
                   •  mentioned above the primary treatments are behavioral interventions that include educating the infant’s primary caregivers on methods for creating a physical and social environment that promotes language development.
                   • there has been a push for all families, regardless of clinical or socioeconomic status, to limit infants’ screen time, such as television view- ing and smartphone or tablet usage, experienced by infants - + caregivers use of devices
                   • even the presence of interactive toys (those that make an electronic sound or automatic movement in response to manipulation) as opposed to more traditional toys (such as nesting cups and balls) has been shown to be associated with reduced infant vocalizations and parent responses to infant vocalizations
                   • the controversies center around the perspective that members of groups consid- ered “at risk” should not be pressured to conform to a pattern of development that is typical with reference to some particular cultural standpoint.
                   • conduct research that is cultur ally sensitive and appreciates the multidimensionality of infant development and the trade-offs of risks and benefits of various perspectives and practices, 
                   • and to present research findings in a way that is descriptive and informative but not prescriptive or judgmental.
             • Brain/neural
               • Brain networks that support language processing in the adult are already present in the infant brain. 
               • Speech activates a language network that  includes primary and associative auditory regions, as well as frontal and pre- motor areas including the superior temporal gyrus (Wernicke’s area), the planum temporale, and the inferior frontal gyrus
               • Key regions in this network are already activated by speech stimuli in premature infants, suggesting that the foundations of the language network are driven by intrinsic rather than experiential factors
               • clear asymmetries in speech processing in adults, speech pro- cessing in newborns is more bilateral, although conflicting results have been found in the field that complicate the interpretation.
               • Lateralization of language processing in the adult brain has been hypothesized to arise from differences in how auditory association regions process the temporal features of the acoustic signal
               • asymmetrical timing model hypothesizes that the left and right hemispheres sample the incoming auditory signal at different rates – the left with a time window optimized to capture phonetic information, and the right with a time window optimized to capture syllabic information.
               • By 3 months of age, speech also engages prefrontal cortical areas that have been implicated in word recall, and may reflect a growing familiarity with speech input
               • +
                 • speech and prespeech vocal motor control relies heavily on the recruitment of neural circuitry that previously evolved for the production of reflexive vocal signals such as cries and laughs or other reflexive vocal tract movements,
                 • according to this theory, the fact that the onset of rhythmic babbling does not occur until about 7 months of age would be related to delay in maturation of the chewing jaw movement circuitry, 
                 • and possibly could be related to the time it takes for children to learn to combine phonation with jaw movement.
                 • Having robust direct motor cortex connections to the neurons that immediately affect vocal tract muscles suggests a greater role of motor cortex in the generation of vocalizations in humans.
                 • electrocorticography of the lateral sensorimotor cortex has revealed that when adult humans produce tongue and lip movements to make specific speech sounds, such as /b/, /d/, or /g/, there is a corresponding rise in activation of the primary motor cortex regions associated with the body part
                 • computational mod- eling studies (see the next section) have demonstrated how cortical learning mechanisms can readily account for some of the changes we see in vocal pro- ductions across the first year of life in typically developing infants,
                 • seems likely therefore that there is a route for cortical motor learning that does not rely on additional circuitry for generating patterns of vocal tract muscle activation for mastication or for reflexive vocalization.
             • +
               • higher socioeconomic status (SES), usually measured through parental, espe- cially maternal, educational attainment and sometimes including income, is associated with faster language acquisition by infants
               • higher SES was associated with increased infant volubility (i.e., infants vocal- ized more often) but did not detect any relationship between SES and the age of onset of canonical babbling
               • Early productive vocabulary development, on the other hand, is clearly pos- itively correlated with SES.
               • If there are indeed language-related differences in newborn cry, this could be due to infants’ subconsciously processing the acoustic patterns to which they have been exposed and modifying their reflexive vocalization acoustics to match.
               • alternative explanation could be that differences in caregiving practices across cultures lead to different intensities of cry and subsequently different average cry acoustics - controversial topic questionable
               • The controversy stems from the fact that the tran- scribers were knowledgeable about the infant’s home language, had access to the ambient language the infants heard during the naturalistic recordings, and spoke the same language as the home language of the infant whose babble they transcribed,
               • early word production, there do appear to be some consistencies that may be driven in part by language- universal constraints on motor control and cognition.
         • Computational Models
           • Distributional learning is not the only proposed mechanism for phonetic cat- egory learning. 
           • Indeed, computational models suggest that the distributional statistics alone may be insufficient in naturally heard language to support pho- netic category development
           • Computational modeling is used to formulate and test theories about how infants learn to produce both more mature-sounding vocalizations and meaningful speech.
           • earliest computational model is connectionist models - The coactivation of perceptual neurons and motor neurons allows for self- organized learning of the correspondences between motor commands and perceptual consequences.
           • One challenge for models of this type is that different individuals have dif- ferently shaped vocal tracts and therefore differences in the range of acoustic features they can produce.
       • Speech segmentation
         • This occurs both within and between words, leading to a con- tinuous auditory signal without clear breaks to demarcate word boundaries.
         • The auditory speech stream contains a number of cues demar- cating word boundaries, including statistical regularities, prosodic stress pat- terns, phonotactic regularities, and allophonic variations.
         • Prosody is one cue to word boundaries. Infants show sensitivity to the pros- ody of their native language by 6 months
         • Another cue to word boundaries is phonotactics, which constrain the possi- ble ordering of sound segments in a word.
         • however this ability is constrained by infants’ previous experience with speech sound combinations; 9-month-olds are able to identify word boundaries when they are delineated by commonly occurring phonotactic sequences
         • For infants to learn the stress patterns and phonotactics that signal word boundaries in their language, some initial speech segmentation must take place.
         • The word-form recognition studies overlap considerably with the word seg- mentation studies.
   • Infant Word Learning and Emerging Syntax
     • Remarkably, in spite of the diversity of infants’ language experiences across the globe, all children learn language.
     • They do so using a panoply of intersecting processes, including attention and statistical learning, together with principled assumptions such as the whole object bias, all within the con- text of socially communicative interactions.
     • Many additional biases including the shape bias are learned via experience, building on these existing processes.
     • Infants’ brains are prepared for language input, and their language experiences continually transform the structure and function of the brain.
     • sociocultural differences in infants’ language environments worldwide as well as socioeconomic differences within societies, 
     • language development is universally benefitted by speech that is directed toward the infant and that is of high quantity and quality.
     • Dual Language Exposure and Early Learning
       • Longitudinal research with larger and more diverse samples of children are needed to truly understand how variability in dual language learners’ envi- ronments contribute to language and cognitive development.
       • the theoretical framework for bilingualism has been used to study trilinguals, and most studies do not distinguish between bilinguals, trilinguals, or multilinguals
       • More research characterizing different children’s language experiences, and how they vary across social contexts, will illuminate how to approach inter- ventions and policies for infants from dual-language or minority-language families.
       • Studies that describe the ways in which parents from different eth- nolinguistic groups use language with their children and whether pedagogical interventions can significantly increase positive cross-linguistic influences are needed
       • The studies reviewed in this chapter suggest, with some exceptions, similar learning mechanisms employed by monolinguals to attend to and process a single language are also used to prepare the bilingual infant to attend to and process their two languages.
       • exposure to multiple languages should be encouraged,  because being able to communicate in another language opens up new literatures, traditions, and ideas to children - greater openness to other cultural groups  and nurture the human connections necessary for optimal neurocognitive development.
       • Bilingualism is common world- wide, but in the United States bilingualism is confounded with poverty, so that children from low-SES backgrounds have lower quality and lower quantity of experiences in both languages
       • Exposure and attention
         • being completely monolingual is quite rare as multilingualism is often the norm
         •  suggest  that simply perceiving and processing sounds from multiple native languages early in life may differentially affect specific attention and learning mecha- nisms, most likely due to neurocognitive adaptations to the early linguistic environment
         • examining the impact of dual-language exposure on early learn- ing during the infancy period provided an important step in understand- ing cognitive trajectories for monolingual and bilingual infants.
         • Infant studies using neuroimaging techniques may also provide support for the hypothesis that early exposure to multiple languages enhances early atten- tional processes.
         • although there was no evidence of a semantic processing delay or semantic processing advantage for bilingual infants, attention to unexpected stimuli seems to hamper semantic integration for monolinguals but boosts integration for bilinguals.
         • parents of bilingual children do not speak more to their children than parents of monolingual children. Therefore, bilingual children must acquire both lan- guages while experiencing reduced input
         • raised in a multilingual environment has the potential to enhance and promote the development of a flexible attention system – possibly triggering a cascade of ramifications for later language, cognitive, and social development.
         • Language
           • Like monolinguals, language tra- jectories of bilingual children are dependent on the quantity and quality of the input they hear in each of their languages
           • Longitudinal studies show that monolingual and bilingual children reach many milestones at similar time points during infancy and have comparable conceptual vocabularies
           • Behavioral studies have reported that phonetic processing and discrimination is somewhat similar for both bilingual and monolingual infants, with some dis- tinctions in timing
           • (fNIRS) paradigm - both monolinguals and bilinguals demonstrated activation in language- specific areas of the brain (left superior temporal gyrus and left inferior frontal cortex), with interesting developmental patterns.
           • One difference between language groups was that older bilingual infants remained sensitive to nonnative phonetic contrasts and the monolinguals did not
           • neural encoding of two languages may take more time and infants with exposure to multiple languages show neural sensitivity to both languages at 11 months of age - bilingual neural activity extended into the prefrontal and orbitofrontal cortex
           • tracking syllable probabilities in multiple languages requires the bilingual infant to segment syllables from two different linguistic codes, possibly requiring increased or distinct engagement of working mem- ory, inhibitory control, and attentional flexibility.
           • +
             • bilinguals and found that bilingual infants could not learn similar sounding words until 20 months of age. This result was puzzling
             • Bilingual children have been shown to be more likely to accept a novel/unusual name for an object than monolingual children, with the hypothesis that bilingual children may recognize that the connection between an object and its label is arbitrary
             • indicate that bilingual infants may begin to use phonetic detail later than their monolingual peers and may rely on the use of relevant language sounds to direct word learning.
             • As this delayed reliance on sounds does not seem to negatively impact overall word-learning capabilities, the authors speculated that bilingual infants may use this initial compensatory approach to deal with the demand of several languages
             • The results indicate that linguistic differences in experience may drive underlying neural activity to words and that there are qualitative differences in brain activity for bilingual versus monolingual children.
           • Memory
             • To learn two languages successfully, it is possible that children who routinely hear complex linguistic input may recruit other cognitive resources for processing.
             • Memory flexibility is vital to the learning process as it allows past experiences to be applied to a range of future scenarios that are not likely to be perceptually the same as the original learning episode.
             • bilingual infants are exposed to more varied speech patterns than monolinguals and are also presented with more opportunities to encode information in a variety of language contexts.
             • This variable linguistic experience may possibly contribute to the enhancement of memory flexibility.
             • suggest that the bilingual infants were able to flexibly recall the visual cues across the different puppets after a 30-minute delay.
             • why? changes in attentional processing and control may directly affect memory processing, age-dependent changes in mf could be due to an early inability to form relational representations, transition to a higher-level hippocampus-dependent memory system, activation of the prefrontal cortex.
             • possible that bilingual infants may organize their memories in a more hierarchical manner and selectively attend to the focal cue, whereas monolinguals attend to extraneous informa- tion such as the color or shape of the stimuli.
             • Social interaction
               • Social interaction is an important aspect of early language learn- ing and infants from monolingual or bilingual experiences may grow up in very different social environments, possibly leading bilingual children to distinct abilities needed in order to successfully facilitate communi- cation.
               • Early exposure to more than one language may pos- sibly enhance their social interaction or communication skills.
               • bilingual environments must track multiple linguistic systems while  encoding linguistic and pragmatic cues from each of their languages – often encountering barriers in communication as they figure out which speakers understand which language.
               • Bilingual children may be able to learn a speaker’s intention by efficientlnt  making use of communicative cues - growing up in linguistically different environments may impact attention to social interaction cues as a way to improve communication between speak- ers
               • A neurodevelopmental disorder that is linked with severe social impair- ments is autism spectrum disorder (ASD).
               • Results suggest that children (ages 24–52 months) with ASD who are exposed to more than one language do not experience additional delays in language development.
               • Sociocultural
                 • There is significant overlap between dual-language learners and children of immigrants
                 • and as ethnic and racial minorities tend to experience more economic and social hardship, studies examining samples of dual-language learners often conflate findings with immigration-related characteristics
                 • Research has demonstrated that most children from immigrant families score in the typical ranges on behavioral and psycho logical assessments
                 • and some studies have found that immigrant children have better social-emotional competence and fewer behavioral problems compared with nonimmigrants
                 • Children from dual-language homes receive reduced linguistic input to each of their languages already, so in theory, bilingual chil- dren from lower-SES households may be at a greater risk as they may not receive enough input in either language.
                 • differences by language group were found for memory flexibility, with both low- and high-SES bilingual groups outperforming monolingual groups.
                 • Implications
                   • As early language ability is a robust predictor of school readiness and later academic achievement
                   • Repeated exposure to words and phrases increases the opportunity to learn and remember the word, although there are no set criteria for the number of exposures needed
                   • important point should be made when comparing children from different linguistic backgrounds. Even though studies have reported that children who are learning two languages have lower levels of language ability in each of their languages compared to their monolingual peers
                   • measured bilingual toddlers’ language skills by combining across both of their languages illustrate that bilingual toddlers either equal or in some cases exceed monolingual toddlers in their rates of vocabulary and grammatical development
                   • bilingual frameworks may also be inappropriate for trilingual studies as well - 
                   • how to approach interventions and policies for infants from dual-language or minority-language families - exposure to multiple languages should be encouraged,
                   • Deviations in neurocognitive trajectories between dual-language learners and their monolingual peers may be a by-product of  adaptations to demanding learning conditions that infants in bilingual environ- ments face.
         • Perceptual narrowing
           • In the first 6 months of life, infants have a capacity to discriminate pho- nemic contrasts (native and nonnative) from most, if not all, of the world’s languages.
           •  By 10–12 months, infants are more highly sensitive to the phonetic contrasts found in their native language – indicating that early linguistic expe- rience shapes concurrent and future language development.
           • This pattern of “perceptual narrowing” also occurs for bilinguals in both of their native lan- guages
     • Problem of reference
       • It is told through research on how children navigate what has been called the problem of reference
       •  – how words map to world, and the problem of syntax or how little minds come to recognize that words are connected to reveal propositions about the world they live in.
       • Statistical learning is a domain-general process of tracking associations in input with- out relying on prior knowledge
       • Word Learning
         • Infants must prune their discrimination of phonemes to those contained in their native language and infants who are better at phonological segmentation have better word-learning skills later
         • garnering even a basic understanding of word meaning is far from a simple challenge that has been termed the mapping problem. 
         • many researchers argue that mere sounds (or gestures for signers) do not reach the status of a word until infants generalize the word to other members of the same category
         • Models of word learning once focused on single mechanisms, but it is now widely accepted that it is a product of several processes working interdepen- dently - social cues, grammatical cues
         • Associative word-learning theories (i.e., cross-situational models) posit that infants store associations between each word and multiple possible meanings of the word, tracking the statistical regularity
         • Hypothesis-testing accounts offer an alternative word-learning strategy, in which infants form a single hypothesis about a word’s meaning in any given ambiguous word-learning situation
         • Bayesian inference models of word learning incorporate aspects of both associative and hypothesis-testing models. Bayesian models posit that word learn- ers entertain multiple word-meaning hypotheses, and, given experience with particular word-learning situations and the use of principled inference proce- dures, the likelihood
         • Emerging Syntax
           • As infants become familiar with more and more words, they notice consistent patterns in the phonology and semantics of their native language that constrain word learning.
           • Among the earliest consistencies infants focus on are phono- logical regularities, including the predominant prosodic stress pattern and phonotactic patterns
           • Infants’ early word learning prioritizes mapping words whose prosodic stress and phonotactic patterns are most common in their native language
           • Infants growing up in bilingual environments simulta- neously learn the phonological regularities of two languages  and bilingual infants are as successful as monolingual infants at learning similar-sounding novel words
           • Importantly, the specific vocabulary items that infants have acquired determine the development of these semantic biases
           • infants’ word learning leads to the development of word-learning biases, which in turn facilitate word learning.
           • these studies suggest that infants gradually acquire grammar in their native language, with later learning (e.g.,  nonadjacent dependencies) building on earlier learning
           • Policy Perspectives: Addressing Socioeconomic Status
             • although there are strong pre- dictive relations between infant language measures and school-age outcomes, including IQ, working memory, language skills, and literacy there is some controversy about the extent of a word gap.
             • Key processes that foster language growth are available early, making the period from 0 to 3 years of age an opportune window of time for high-​impact policies.
             • Interventions that equip caregivers with language- learning techniques are effective at improving infants’ language environment and language skills
             • Interventions seem to be most effective when they start early, have high dos- age,  are sensitive to the home environment  and are continued over time
             • policies should also move towards recognizing that for many children, the language system is comprised of two languages rather than just one, and successful outcomes for bilingual children rely on high-​quality and high-​quantity experiences with both languages.
             • Teaching children two languages in early childhood programs and schools serving children who are English-language learners (ELL) could support the development of language, and ultimately could serve to mitigate the SES gap
             • policies that open the door to more language-​rich or “languagized” experiences throughout communities.  simple and inexpensive as signage in supermarkets, with prompts for adult–child conversation can significantly boost the quality and quan- tity of talk among low-SES families
           • Syntactic bootstrapping
             • Infants’ emerging syntax plays a particularly vital role in verb learning. Verbs are conceptually more difficult than nouns
             • Through a process called syntactic bootstrapping, children use familiar syntactic structures to disambiguate verb referents
             • For example, 2-year-olds hearing a novel verb in a transitive frame (“The duck is gorping the bunny!”) mapped the verb gorping onto a scene of a duck performing a novel action on a bunny, rather than mapping the verb onto a scene of the duck and bunny perform- ing novel actions independently,
             • suggesting that infants are sensitive to the Bayesian principle of “suspicious coincidences”:
             • The prosodic bootstrapping hypothesis proposes that infants take advantage of prosody in speech to identify syntactic boundaries and learn about syntac- tic structure
             • This is important, because much of   conversational speech, particularly IDS, involves back-and-forth communica- tion, in which sentence fragments rather than com- plete clauses are exchanged
             • Additionally, IDS prosody is used by infants as early as 6 months to detect syntactic units smaller than clauses, specifically phrasal units, such as noun phrases
           • Neural
             • precursors of the left-localized adult language system are present at birth, with newborns’ processing of linguistic stimuli – but not nonlinguistic auditory stimuli – lat- eralized primarily to the left hemisphere of the brain
             • However, regions of both hemispheres activate in response to language at birth, and connectivities within this neural network are initially immature
             • plasticity: Children who experienced left-hemispheric strokes within days of birth had normal language skills, with neuroimaging revealing complete reorganization of the language system to right-hemisphere brain areas homologous to the areas on the left that typically subserve language functions
             • First, the domain-general mechanisms with which infants are equipped for finding structure in language are reflected in neural mechanisms present at birth -  Neonates’ brains are sensitive to the statisticalstructure of language, as evidenced by their event-related brain responses toa statistical word segmentation task. 
             • neonates’ brains using near-infrared spec- troscopy (NIRS) further revealed that newborns could differentiate simple repetition-based grammars (e.g., ba-​ba-​mu vs. mu-​ba-​ba); the differential response to these grammars involved neural activity localized in the inferior frontal region
             • Second, language learning is “gated by the social brain” – that is, neural computations of input are largely restricted to signals from humans
             • 9-month-olds’ learning of phonemes from foreign language speech, as indicated by neural phonetic discrimination, was enhanced by the mere presence of a similarly aged peer, suggesting effects of social arousal on language learning.
             • Sociocultural
               • United States, Mexican and Dominican immigrant mothers use more nonver- bal strategies (i.e., gestures) when engaging infants with toys and books relative to African American mothers, who tend to use more verbal modes of com- munication
               • This sociocultural difference in the relative use of verbal and nonverbal communication is reflected in infants’ developing verbal and nonverbal skills
               • More globally, research from non-Western, nonurban sociocultural settings reveals greater diversity in communicative contexts that calls into question the universality of developmental patterns of language growth.
               • the idea of constructing a foundation of communication within a specific caregiver–infant dyad may not be applicable in these sociocultural contexts - sibling primary caregiver
               • In some cultural climates, as in rural Senegal, talking directly to children is even considered taboo, though an intervention suggests that language-learning techniques can be  introduced in culturally sensitive ways, helping caregivers scaffold early lan- guage
               • within the United States, socioeconomic status (SES) disparities in infants’ language skills are well documented by the second year of life and persist across development
               • overheard speech is not as effective as child-directed speech for word learning, and that differences in the quality and quantity of child- directed language, both across and within SES groups, are linked with differ- ences in children’s language skills.
         • Attention
           • To successfully map a word onto its referent in a given situation, infants must attend to the correct referent of the word rather than attending to incorrect alternatives.
           • First, infants’ selective and sustained attention toward objects that are of interest to them provides opportunities for adults to engage in joint atten- tion with the infant – which in turn extends infants’ selective attention
           • Second, word learning demands that infants learn to shift their attention when adults point out objects to them
           • Individual differences in this attention-shifting ability at 6 months predict vocabulary size up to 18 months later
       • IDS
         • Infant-directed speech (IDS) is spontaneously used by adults and children when interacting with infants
         • IDS is characterized by higher and more variable pitches, slower rates of speech, elongated vowels and pauses, phrase-final lengthening, shorter utterances, and greater positive affect
         • While some aspects of IDS, such as exaggerated pitch and emotional expression elicit infants’ attention and may therefore support adult–infant communication broadly
         • there is one feature of IDS that predicts infants’ vocabulary acquisition specifically: vowel hyperarticulation
         • Adults modulate their IDS in real time in response to infant feedback, and their use of vowel hyperarticulation is specifically responsive to infants’ language abilities
         • Furthermore, cross-linguistic differences in the content of IDS have impli- cations for word learning.
   • +
     • While newborn infants can discriminate languages from different rhythmical classes, the ability to discriminate the mother tongue
     • Young infants show broad-based phonetic discrimination.
     • Listening experience over the first year of life attunes phonetic perception such that infants become experts at discriminating the speech sound distinctions used in their native language, with sharpened discrimination of native distinctions
     • This is the dominant pattern reported for many speech sound distinctions including consonants, vowels, tones, and linguistic signs
     • Following experience with these pairings, 9-month-olds were better at discriminating the phonetic contrast than they were if the two words were paired interchangeably with the objects
     • infants begin to recognize not just word forms, but actual word–object pairings by as early as 6 months of age, many in the field have begun to speculate that this early word learning might simultaneously support native phonetic category learning.

10. Infant Attachment

    • The main tenet of attachment theory is that infants’ tendency to form relationships with their primary caregivers is an existential need.
    • The second main tenet of attachment theory is that the quality of the infant–caregiver attachment relationship varies depending on the caregiving environment and specifically on the caregivers’ sensitivity to the infants’ proximity seeking cues and communications
    • proximity and contact with a spe- cific caregiver, and to do so when one is distressed, i.e., in need of physical and psychological security
    • Attachment theory thus assumes that all infants, regardless of their cultural niche, are innately biased to become attached to primary caregivers.
    • environmental influences on attachment quality were correlated with the qual- ity of maternal sensitivity, suggesting that the central environmental variable influencing attachment quality is the caregiving environment.
    • A third central tenet of attachment theory is that the quality of infant– caregiver attachment shapes one’s future relational patterns in the form of expectations, attitudes, and beliefs regarding the self and others.
    • Emotional development
      • pet, emotion appears to be a central motivator of infant action. Infancy is also characterized by rapid emotional development.
      • Neonates exhibit high rates of crying, but by 6 months broad-mouthed smiles are a common feature of social play. Infants develop sadness expressions in the first year, demonstrate empathy by 2 years, and pride by 3.
      • Temperament
        • detective. Why is the baby crying? Is he/she hungry? Cold? Too hot? Angry? Gassy? Tired? Bored?
        • caregivers play an important role in modulating infants’ emotional experiences, since much of emotion regulation is first implemented externally until the child can internalize and develop effective stand-alone reg- ulatory responses.
        • (i.e., emotion, emotion regulation, and temperament) share five core features. First, all three components reflect aspects of functioning that are related to social and psychological well-being
        • Second, all three have a constitutional/reflexive basis that is likely genetic in nature, but quickly devel- ops into relatively less automatic and more elaborate forms with the matura- tion of brain and physiological systems in the first 2 years of life
        • Third, basic attention processes that allow the infants to select, orient to, disengage, or shift from rel- evant stimuli in the environment
        • Fourth, the development of emotion, emotion regula- tion, and temperament influences, and is influenced by, the infants’ experience of the social environment
        • Finally, emotion, emotion regulation, and infant temperament are multilay- ered complex phenomena involving physiological, neural, and cognitive com- ponents that may work in parallel or interact to give rise to observed behavioral reactions.
        • Basic constructs
          • understand how early biological predispositions (including temperament) interact with the socioemotional environment during infancy to shape early patterns of adaptive and maladaptive behavior.
          • By emotion, we refer to an evolutionarily adapted set of physiological, neural, cognitive, behavioral, and subjective reactions, triggered by the detection of a personally significant event in the environment.
          • By emotion regulation, we specifically refer to the processes that lead to changes in the occurrence, valence, intensity, duration, and timing of the physiological, neural, cognitive, behavioral, and subjective components of infants’ emotional reactions to the environment
          • By temperament, we refer to biologically rooted individual variations in children’s emotional, attentional, and motor reactions to the environment as well as variation in their regulation of these reactions
          • Behavioral markers
            • an infants’ expressions of emotion directly reflect their experience of emotion
            • the systematic observation of infant regulatory strategies relies highly on   observing changes in a child’s emotional reaction in situations that elicit an ini- tial emotion.
            • Attentional strategies (e.g., shifting gaze away from the dis- tress elicitor and towards the mother), 
            • self-comforting (e.g., touching the   head, bringing hands to mouth, thumb-sucking), or
            •  active avoidance (e.g., arching the back or pushing away, withdrawing the hands, or retracting the  arms).
            • Neural
              • The most rapid and radical developmental changes in the structure and functions of brain systems occur in the first 2 years of life
              • A ventral system consisting of amygdala, the insula, the striatum, and the medial orbi- tofrontal cortex is involved in relatively nonvoluntary and rapid responses to motivational goals.
              • a dorsal system consisting of the lateral and medial prefrontal cortex, the lateral orbitofrontal cortex, and the anterior cingulate cortex is implicated in the more effortful processes underlying the regulation of emotional experiences.
              • over the course of development, the key structures in the ventral and the dorsal systems are interconnected, mutually influence one another, and operate together to give rise to observed emotion
              • together, it seems that our measures of brain activity reflect the cooperation and interaction of emotional arousal as well as regulatory pro- cesses, just like our measures of infants’ observable behavioral responses.
              • Changes in heart rate seem to go hand in hand with changes in the expression of negative affect, thus its regulation
            • Regulation and temperament
              • Although infants show some rudimentary ability to regulate their own emotional experiences in emotionally arousing situations, these initial capabili- ties are limited to more reflexive strategies such as sucking or visual reorienting   and have a limited effectiveness in regulating
              • Although still primitive, the first forms of vol- untary regulation start to emerge at around 3 months of age.
              • Infants’ emotion self-regulation abilities in the early months of life are highly social in nature and rely on parents’ assistance as external sources of regulation
              • A shift from more reflexive and primitive to relatively more elaborate and active forms of emotion self-regulation emerges in infants between 3 and 7 months thanks to maturational changes in attentional, motor, and cognitive systems
              • temperament encompasses individual differences in the response to specific stimuli, particularly those that convey threat, novelty, and reward.
              • that temperament is centered on a child’s reactivity and subsequent regulation in response to the environment, but it need not center on the child’s reactivity to and subsequent regulation of emotion.
              • temperament assessment battery (LAB) is designed to assess patterns of expressed emotion and behavior by manipulating events putatively linked to anger (arm restraint), joy (peek-a- boo), and fear (stranger approach), among others.
              • +
                • Among many temperament researchers, 4 to 6 months of age is a critical win- dow into “pure” temperamental reactivity before variation in temperamental regulation can systematically take hold.
                • As the overall expression and intensity of emotion decreases with age, it can become more difficult to capture distinct markers of temperament.
                • second methodological strategy has been to incorporate biologi- cal and cognitive markers of temperamental variation. In initially describ- ing the temperamental trait of behavioral inhibition - amygdala response
                • In addition, cognitive measures, such as attention biases, are also evident early in life
                • One benefit of a multi-method approach is that it allows researchers to examine measures across a wider age range, making it easier to examine rank-order stability in the individual response to the environment,
                • even in the face of developmentally expected changes
                • Taken together, the evi- dence supports the differential susceptibility hypothesis, showing that temperamentally negative infants’ emotion regulation skills are more susceptible to parenting influences both “for better and for worse”
                • Development
                  • The experience-expectant and experience-dependent nature of emotion development suggests that child temperament may modulate both how emotion generation and regulation processes emerge and the extent to which  extrinsic contextual/environmental influences shape their emergence.
                  • development, temperament and contextual forces may interact to determine emerging trajectories of emotional development. The dynamic interactions between infants’ temperament and contextual influences are at the center of diathesis-stress/dual-risk
                  • Diathesis-stress/dual-risk models primarily focus on the increased vulnerability of temperamentally negative children in the face of environmental or contextual adversity,
                  •  whereas differential susceptibility models extend the idea of a greater sensitivity/receptivity of temperamentally negative chil- dren to supportive/positive contextual influences.
                  • Parenting
                    • that the moderating role of child temperament on parental influences has only recently been incorporated in infant emotion research  
                    • This may reflect underlying presumptions regarding the maturational progress of the earliest emotions, relative to the clear evidence of emotional variability in older children.
                    • Theoretical accounts of early emotional development - that parents’ positive emotional expressions, and their accompanying synchronous and sensitive responding to infants’ emotional expressions, provide the main framework for both the early experience and regulation of emotion
                    • observational studies consistently find that young infants seem to instantly tune in to changes in their parents’ expressions of emotion and their emotional expressions seem to mirror those of their parents during these interactions
                    • Infants’ self-regulatory capacity develops within early relationships with caregivers.
                    • on parenting dimensions that relate to the early parent–child relationship, such as mutual responsivity, synchrony, attachment security, or to parents’ interactive quality such as emotional synchrony, availability, and sensitivity
                    • On the flip side, lower levels of maternal emotional availability and sensitivity, as well the lack of secure attachment, seem to have stronger links to emotion regulation in children with high levels of temperamental negative affect.
                  • Cultural
                    • Shifting slightly our view of this relation, we can also see that specific temperamental traits can elicit targeted parental socialization attempts
                    • valued traits. These behaviors, in turn, are shaped by cultural expectations of adaptive and “ideal” profiles of emotion and emotion regulation
                    • Parents will shape and mirror acceptable emotions and reinforce preferred emotion-regulation strategies . For example, Western mothers tend to minimize signs of shyness in children, particularly in boys, but are unlikely to discourage boisterous exuberance
                    • up until recently, one often saw increases in behavioral inhibition over time in mainland China.  This reflects the traditional values of demure or reserved demeanor. Indeed, inhibited children were often held up as leaders in their school community
                    • Cultural norms and ideals also shape how we come to assess maternal sensitivity.
                    • Although infants typically express a fairly standard array of emotional signals early in life, variation is initially introduced with the emergence of temperament-linked profiles of emotion and emotion regulation
                    • Quickly, however, we see culture-specific transformations of these expressions into socially embedded communicative signs - For children whose initial temperament does not match the cultural ideal, there is an additional pull on emerging regulatory mechanisms
                  • Implications
                    • Given the pervasiveness of emotional processes in everyday life, we need to better understand and identify points of risk. 
                    • With this knowledge, early interventions can target mechanisms that shape the individual, the context, and the interactive relation between the individual and the environment.
                    • examined together in order to generate a three-dimensional view of emotional development in infancy: person, timing, experience, and context
                    • With respect to person, we need to assess individual variation across multiple levels of functioning.  This involves the expression of emotion, the contextual forces that trigger emotion, biological correlates, and cognitive profiles.
                    • Within and beyond the person, new analytic approaches can capture the tim- ing of emotion over time, helping extract regulatory mechanisms and eventual socioemotional outcomes.
                    • The next broad goal is to couple the timing of personal responses with specific experiences. At a small-scale level, this can encompass exposure to con- strained triggers that are designed to elicit variation in emotional displays – the LAB Tab, for example,
                    • context. Oddly enough, although this is the most overarching component of interest in our work, we often ignore or overlook its influence. That is, we constrain experimental studies, or narrowly define more descriptive studies,
      • Theoretical considerations
        • Theories of emotional development differ as to the defining features of infant emotion and how emotions develop  
        • They offer competing perspectives on how behaviors such as crying are associated with emotional states such as distress.
        • Developmentalists have long posited that emotional development involves the emergence of more differentiated emotional states from more diffuse states - cognitive understanding as a defining characteristic of emotion
        • Discrete emotion theory
          • Discrete emotion theories regard core affective feelings as the defining fea- ture of infant emotions
          • The elation of joy or the   dejection of sadness are thought to be developmentally invariant character- istics of emotion states.
          • These feeling states are hypothesized to be the prod- uct of discrete affect programs that also output specific patterns of expressive   action such as facial expressions
          • As neurophysiologically based affect programs give rise to both expres- sive actions and feelings, the expressive actions are thought to typically index   feeling states during infancy
          • Through its emphasis on facial expressions as markers of feeling states, discrete emotion theory can be thought of as the implicit theoretical basis for the vast quantities of research that use facial expressions
          • Negative emotional development
            • facial movements involved in cry faces appear to be part of an early developing muscular synergy such as those proposed by dynamic systems theorists
            • Undifferentiated distress manifested in cry faces and accompanying cry/fuss vocal expressions are the most salient and common expressions of negative emotions in the first months of life.
            • Proportions of full-face and blended expressions did not differ or change with age, indicating that discrete expressions of negative emotion are not more common than blends.
            • More radically, the anger constellation may be an attenuated version, and perhaps the developmental outgrowth, of the cry-face (distress) expression
            • adult judgment studies suggest that through 2 years of age infants display a generalized distress-linked emotion expression rather than discrete facial expressions of anger, fear, and sadness
            • increasing specificity of discrete facial expressions to targeted emotion elicitors in the first year of life, although few infants produced the target expres- sions overall - suggest overlapping but distinguishable anger and sadness states as early as 4 months of age.
            • infants who exhibited higher increases in anger also exhibited higher increases in sadness, suggesting these were not entirely disparate emotional reactions - Toward 1 year of age, there is evidence that infant body movements reflect dif- ferent emotional states
            • Positive emotional development
              • Infant smiles vary continuously. Degree of zygomaticus major contraction determines a smile’s strength, Duchenne smiles are a well-known signal of joy, which may index reciprocated positive affect in infants.
              • In full-term neonates, smiles with strong zygomaticus major contraction and the Duchenne marker occur in roughly equal proportion to weaker smiles without eye constriction (Dondi et al., 2007; Messinger et al., 2002). Although stronger Duchenne
              • Laughter emerges  2 and 5 months, Transition to Social Smiling Between 1 and 2 Months, in Interactive Smiling Between 2 and 6 Months
              • The FFSF protocol is well suited to examining dynamic changes in infant positive and negative affect. In the FFSF, an episode of face-to-face play is 
              • followed by the still-face episode (in which the parent maintains a still face and does not respond to the infant’s bids) and then a reunion episode
              • Descriptive data suggest that infant and mother continuously affect one another’s joyful expressions such that stronger infant smiling is mirrored by stronger mother smiling
              • Between 6 and 12 months, infants become increasingly intentional communicators, and are more likely to coordinate smiling with gestures and gazes that reference objects and events - intentionally smiling, anticipatory smiling
              • The general Duchenne intensification hypothesis,
                • which posits similarities between smile and cry-face expressions. A dynamic systems perspective suggests that specific facial actions may have similar functions across positive and negative expressive configurations.
                • Both smiles and cry face can involve the Duchenne marker – eye constriction produced by the muscle orbiting the eyes (orbicularis oculi, pars lateralis).
                • Electrophysiological evidence suggests greater left than right cerebral activation during Duchenne smiles than non-Duchenne smiles in 10-month-olds a pattern associated with approach motivation in adults
                • The opposite pattern of electroencephalograph (EEG) asymmetries was observed during sadness and anger expressions with strong eye constriction
                • Smiles during the positive-emotion-eliciting face- to-face play episode were more likely to involve eye constriction than smiles occurring during the negative-emotion-eliciting still face.
                • The general Duchenne intensification hypothesis was also tested using objective measurements (computer vision) of the intensity of facial actions
        • Functionalist theory
          • While discrete theories hold that emotion exists within the individual, function- alist theory holds that emotions are defined by maintaining and altering rela- tionships with the social environment
          • Sadness, for example, func- tions to elicit succor and tenderness from caregivers.
          • Sociocultural theory
            • Sociocultural theory considers the proximal cultural rules and scripts that guide interactions as the rubric in which emotional development occurs
            • preverbal expressions of infant emotions develop more culturally meaningful forms. .
            • Depending on cultural values, expressions of infant emotions are differentially imitated and imbued with linguistic meaning
            • Dynamic systems
              • A dynamic systems approach focuses on emotional process as the transac- tion of multiple interfacing constituents including expressive actions, physi- ological arousal, and the social surround
              • Emotion is thought to be the emergent outcome of the bottom-up inter-relationship of neural, expressive, social, and physiological constituents.
              • The differentiation perspective, for example, highlights the development of self-referential cognition as critical to the emergence of emotions such as empathy. 
              • This perspective is consonant with a dynamic systems emphasis on the bottom-up interplay of nonobvious constituents in emo- tional development.
              • Neural
                • At the same age at which infants exhibit differential responses to emotional facial expressions, they also exhibit differential responses to affective prosody. 
                • Words spoken with angry prosody are more attention-capturing indexed by the heightened amplitude of the Nc component in frontal and central scalp regions – to 7-month-old infants than those spoken with happy or neutral prosody
                • sad vocalizations elicit significantly greater neural activation in brain regions that support processing of affective stimuli, including the insula and orbitofrontal cortex,
                • amplified response to negative stimuli such as a fearful face or an angry tone of voice suggests increased allocation of attentional resources to negative affective information that may be associated with negative consequences for the infant.
                • Spontaneous facial expressions involve an extrapyramidal pathway involving subcortical structures, such as the basal ganglia, and deep cortical structures, such as the amygdala, which communicate with the facial motor nucleus
                • suggest that orbitofrontal activation is especially responsive to posi- tive emotional expressions from known and, arguably, rewarding individuals.
                • understanding of the neural correlates of emotion expression, and the asso- ciation between neural responsivity to emotional stimuli and the infant’s pro- duction of emotional behavior, will require a new generation of research activity.
                • Empathy
                  • Empathy, sharing another’s emotional experience, is not a discrete emotion such as happiness, sadness, or fear.
                  • the development of   empathy reflects the confluence of behavioral, cognitive, and expressive fac- tors that characterize the emergence of emotional functioning more broadly.
                  • empathic concern, and hypothesis testing increases sig- nificantly from 13 to 25 months, and the entire repertoire of prosocial behaviors is observable by 2 years
                  • genetic concordance for individual differences in empathy emerged at 20 months and increased through 36 months in a separate study, while shared environmental effects that were evident at 14 months gradually declined with age
                  • Along with maternal responsiveness, infants whose mothers were rated as exhibiting greater warmth were more empathic at 14 and 20 months
                  • understanding the intersecting roles of hereditary and caregiver responsiveness on empathy development will require increased attention to genetic correlates of parental behavior, parental warmth, and gene by environment interactions
                  • Culture
                    • Western and more educated mothers value expressions of positive emotion in their infants, and tend to try to elicit these expressions during dyadic interactions
                    • Mothers from subsistence cultures, on the other hand, tend to value quiet contentment in their infants, and focus on soothing them.
                    • Nso mothers engaged in more body contact and fewer face- to-face interactions. By contrast, German mothers increasingly engaged in face-to-face interactions and exhibited increases in vocal contingent respon- siveness
                    • Nso mothers report breastfeeding to help their infants regulate negative emotions, while German mothers report breastfeeding pri- marily to satisfy hunger
                    • Maternal imitation of infant smiles was associated with increases in the dura- tion of infant smiles in the German sample at 8 weeks, but was not evident in the Nso sample until 12 weeks.
                    • not reveal differences in the likelihood a mother would pick up and hold her distressed infant
                    • practices, and infant emotionality are part of larger cultural and societal sys- tems. They reflect implicit and explicit beliefs about what is necessary and ideal in a developing child
                    • Implications
                      • Cultural diversity has policy implications because of the multi-ethnic nature of most Western societies, and the degree to which American society is host to diverse parenting cultures associated with differences in ethnicity and income
                      • Thus, generous parental leave policies are impera- tive in allowing both mothers and fathers adequate time to build relationships with their infants.
                      • The recognition of expressions of pain in the young infant remains an impor- tant policy issue in neonatal medicine
                      • the increase in electronic media exposure and active digital use by infants is concerning
                      • First, reports on infant facial expressions would be enhanced by document- ing their correspondence with related expressive vocal and bodily actions.
                      • Second, by incorporating potential behavioral attenuators of expres- sive actions, research on temporal associations would, in turn, elucidate the development of infant mechanisms for regulating emotion
                      • Third, low levels of concordance between emotion-eliciting contexts and facial expressions of discrete negative emotion might lead investigators to pursue such investigations at later ages in the hopes of detecting clear evidence for expressions of discrete emotion states.
    • Internal models
      • These self–other schemas are also known as internal working models and are thought to consist of a well-organized, yet dynamic representa- tional structure that is hypothesized to operate primarily outside of conscious awareness
      • Consistent with the psychoanalytic and evolutionary roots of attachment theory, internal working models are thought to serve as defenses against threats to the psychological well-being of the individual
      • Internal working models are assumed to influence the individual’s attentional biases and to involve processes that affect memory and the interpretation of events
      • cross-cultural attachment research suggests that the attachment phenomenon is universal in nature, and at the same time that its univer- sal characteristics may manifest in unique ways depending on the cultural norms.
      • Universality and specificity of attachment patterns across cultures are both essential constituents of attachment theory, attesting to its cross- cultural validity.
      • Attachment assessment
        • In infancy, attachment strategies are assessed with a 20-minute laboratory procedure, which has become the gold standard for infant attachment assess- ment: the strange situation procedure
        • The SSP is valid for assessment of infants aged 12–18 months, and is administered to both the infant and its caregiver in a setting of a room equipped with toys that encourage exploration of the environment.
        • The SSP is designed to assess infants’ expectations of their parents’ availability at times of need by observing their behavior when reunited with parents following brief separations.
        • In the course of two separations and reunions with the caregiver, and having been in the room with a stranger while the parent is both present (before leaving) and absent, infants are assessed for their use of the caregiver as a secure base from which to explore their environment
        • Although the SSP has produced massive amounts of meaningful findings, it has been criticized for its limited ecological validity. 
        • Criticism has focused mainly on the reliance of SSP on a laboratory environment, and for being restricted to the beginning of the second year of life,
        • evaluate the child’s secure-base behaviors, reflecting such features of receiving support from an attachment figure at times of need and using the caregiver to freely explore the environment when the infant is not distressed
        • The strange situation
          •  cry. When the caregiver returns, most infants tend to seek proximity and contact with the caregiver. Infants are normally able to become soothed and comforted by their caregiver relatively quickly, and resume their exploration and play in the room.
          • avoiding the caregiver after she returns, looking away, or rejecting the caregiver’s attempts at contact. These infants are classified as insecure-avoidant (type A) attachment.
          • Insecure-avoidant infants are characterized by distant, self-reliant behav- ior when distressed in the presence of the caregiver
          • Infants in the third group tend to protest and show excessive distress when the caregiver leaves the room, and appear angry with the care- giver upon reunion - insecure-resistant or insecure-ambivalent (type C) attachment.
          • organized attachment strategy; they adapt to the behavior of their attach- ment figures.
          • Disorganized attach- ment is believed to reflect an insoluble dilemma, where infants perceive their caregiver as a haven of safety and at the same time as a threat
          • Socioemotional outcome
            • Cumulative evidence from research over the past five decades has supported the association between the infant’s quality of attachment and socioemotional outcomes in childhood.
            • children who were classified as securely attached as infants and in early childhood showed better socioemotional outcomes than did insecure children, 
            • as indicated by the quality of peer relationships, and by internalizing and externalizing behaviors
            • It is clear therefore that the early infant–caregiver relationship plays a crucial role in the socioemotional trajectory of the individual.
            • Consistent with the notion that the caregiver provides a sense of safety and a secure base to which the child can retreat in times of need to alleviate negative affect and arousal
            • Research on the mechanisms explaining the association between attachment patterns in early life and later maladaptive socioemotional outcomes has focused on children’s stress responses at both the hormonal and neurodevelopmental levels.
            • HPA
              • Of several stress physiology biological markers, the HPA axis has been most extensively researched. 
              • The HPA axis is a key physiological stress reactivity system, of which the hormonal product, cortisol, affects many aspects of neurobe- havioral development in humans
              • HPA axis activity in general, and levels of cortisol secretion in particular, are strongly influenced by early childhood attachment relationships
              • HPA axis function can be examined by assessing the diurnal rhythm of cortisol, which typically emerges at the age of several months and matures through the preschool years.
              • The diurnal rhythm is characterized by a peak in cortisol levels in the morning, followed by a decline throughout the day
              • Both diurnal cortisol and cortisol reactivity to stressors have been found to be affected by parental sensitivity and attachment quality
              • threats to early attachment relationships, such as early care- giving adversity in the form of neglect or placement in foster care, have been consistently linked with children’s low levels of morning cortisol and blunted rhythms across the day
            • Neural
              • evidence has emerged regarding the role of early attachment relationship quality in stress responses, as observed in the developing brain, drawing attention to the brain circuitry underlying the observed behaviors
              • studies have demon- strated the influence of persistent stressful caregiving environments, on the programming of circuitry underlying emotion processing
              • early experiences of stress that occur in association with attach- ment insecurity influence neural development in sensitive brain regions respon- sible for emotion encoding and regulation, including the amygdala
              • One measure of affective neurodevelopment in the context of attachment and its correlates has been amygdala volume.
              • Early attachment insecurity has been shown to also influence amygdala function and functional connectivity to the medial prefrontal cortex (mPFC), a brain region highly involved in emotion processing and regula- tion
              • insecure infant attachment (as assessed with the SSP) was found to be associated with both greater amygdala volumes and emotion regulation processes in early adulthood
            • Sociocultural
              • Bowlby (1969, 1982) suggested that the attachment relationship infants form with their caregivers is the outcome of an innate evolutionary bias.
              • The universality of the infants’ bias to become attached, regardless of the cultural niche to which they happen to belong, is a core element of attach- ment theory.
              • In some cultures, for example, touching or stroking the infant is considered an appropriate response to vocalization; in others, imitating the sound that the infant made or smiling at the infant would be considered more appropriate
              • the ways in which infant distress is attended to differ widely across cultures. Soothing by nursing or feeding, for example, is far more common in non-​Western than in Western cultures
              • The sensitivity hypothesis
                • Across cultures, attachment security also depends on childrearing anteced- ents, in particular sensitive and prompt responses to the infants’ attachment signals, as the “sensitivity hypothesis” postulates
                • The sensitivity hypothesis is further confirmed by findings showing a strong correlation between maternal beliefs about the ideal sensitive mother and attachment theory’s descriptions of such mothers in 26 cultural groups from 15 countries
                • there is evidence that the rates of contingent responding are rather similar across cultures, but also that responsiveness is channeled through culture-dependent modalities
                • Universality hypothesis
                  • According to the “universality hypothesis” all infants without severe neurophysiological impairment become attached to one or more caregivers. 
                  • The universality hypothesis has received strong support from cross- cultural studies.
                  • At the same time, when considering the caregiving arrangements, culture- specific patterns and local customs must be taken into account.
                  • The universality hypothesis has received strong support from cross- cultural studies. The three organized attachment patterns – secure, avoidant, and resistant
                  • infants’ exploration behaviors and their ways of expressing attachment needs have been found to vary depending on cultural norms and customs.
                  • Normativity hypothesis
                    • Attachment theory also predicts that in environments that do not inherently threaten human health and survival, most infants are securely attached.
                    • strong cross-cultural evidence for the normativity hypothesis, and nearly all cross-cultural studies have classified most infants as securely attached
                    • Competence hypothesis
                      • Last, according to the “competence hypothesis”  infant secure attachment leads to positive child outcomes in a variety of devel- opmental domains.
                      • Despite the remarkable finding of an asso- ciation between attachment and health status, the cause–effect relation between attachment security and nutritional status is not entirely conclusive.
                      • It is not unreasonable to assume that healthier infants induce more care in general, and in particular more sensitive care, especially if economic deprivation compels parents to be selective in their investment of time and energy
          • Parental
            • The additive hypothesis draws support from studies showing that infants who are securely attached to both parents have the best outcomes, followed by those who are securely attached to only one parent, and finally by those who are insecurely attached to both parents.
            • buffering hypothesis, according to which early secure attachment to one parent offsets the risks posed by insecure attachment to the other.
            • horizontal hypothesis suggests that infants with secure attachment to either parent have developmental out- comes similar to those with secure attachment to the other parent.
            • To conclude, little attention has been paid to the integrative effect of attachment relationships to both mothers and fathers on developmental outcomes, and the question has remained unanswered for a long time
            • Implications
              • Early infant network of attachment models may func- tion as more complex, more thoroughly elaborated, and more ecologically valid predictors of developmental outcomes than the ones that have been conceptually and empirically formulated.
              • understanding infant attachment as part of an attachment network may broaden the scope of attachment theory to include non-​Westernized cultures in which a common rearing practice includes nonparental caregivers
              • It is important that researchers and practitioners work together to develop future parent curricula that can be implemented as part of high school and university education.
              • There is a need, therefore, to develop policies that will ensure high standards of group care. It has been well established that the quality of early group care matters, and that low-quality settings produce negative developmental outcomes
              • formulate family policies that would enable more flexible work arrangements that recognize childcare as a prime societal concern - Another childcare policy matter of considerable importance pertains to the issue of an increasing number of children who grow up with divorced parents
              •  This includes reexamina- tion of parental leave policies that often require parents to return to work too soon after childbirth, either because of company policy or because of financial necessity

11. Crosscultural

    • continuing task of parents to enculturate their infants by preparing them for the unique physical, psychosocial, and educational situations that are characteristic of the culture in which their offspring are to adapt and develop.
    • Human beings do not grow up, and adults do not parent, in isolation, but in multiple contexts. One significant overarching context in which infants develop and parents parent is culture. 
    • Parent–infant relationships lie at the heart of a nested series of bioecological systems - Bronfenbrenner miccro macro systems
    • Cross-cultural developmental research has many aims, but prominent among them are to inventory and compare similarities and differ- ences in parent–infant interactions in different cultures.
    • What are the universals of infant development and infant care in our species? How do infants participate in and shape their interactions with caregivers?
    • No study of a single culture can answer these broad questions - learn lessons from different cultures that may shed light on them.
    • such lessons may illu- minate which presumed universals of infant development and care obtain across different settings, how infant experiences in different settings affect future child development, and how different settings shape parenting
    • WEIRD-countries
      • still too little is known about the activities and development, life circumstances and experiences, of infants and their parents in non-​WEIRD (i.e., Western, educated, industrial- ized, rich, and democratic) cultural conditions.
      • The goals of cross-cultural research in parent–infant interactions – to  remedy limitations reflective of the lack of broad representativeness and the complementary need for proper tests of generalizable theory – are to identify effects that are culture common versus culture specific
    • Parenting - infancy - culture
      • Culture is embedded in the activities of parents and infants, and for this reason many social theorists have asserted that the family generally, and the parent–infant relationship specifically, constitute the effective crucible for the early  development
      • Human cultures have different adaptive goals, and parents in different cultures have developed different institutions and structures to instantiate paren- tal cognitions about infant care and to implement parental practices.
      • culture, they follow prevailing “cultural scripts” in infant rearing. Those scripts include, for example, when and how to care for infants, what infant characteristics are desirable, and which parenting practices are accepted
      • Cross-cultural comparisons show too that virtually all aspects of parenting infants – whether cognitions or practices – are fashioned by culture.
      • Parenting is therefore a principal reason why individuals in different cultures are who they are and often differ so from one another.
      • The ways that parents engage in these different domains of parenting are culturally situated, and thus parenting practices reflect cultural ideologies and values.
      • Culture
        • cultures consist of distinctive norms, ideas, values, and assumptions about life that are common to a people and that guide and regulate specific practices, including inculcation of valued competencies across generations.
        • Every psychological construct, structure, function, and process has cultural undertones or overtones. Culture is not a static entity either, but rather a dynamic
        • Culture defies easy definition, but most scholars agree that culture embraces patterns of cognitions and practices that distinguish social groups
        • Cross-cultural comparisons are especially valuable because they expose and deepen understanding of processes that generalize across or are specific to disparate populations.
        • Identifying what is culturally common and what is culturally specific biologically and psycho- logically is theoretically significant in neural, behavioral, and social science.
        • Cross-cultural developmental data demonstrate that psychomotor differences among infants in some substantial degree reflect the influence of parents’ infant- rearing practices and that those practices vary with culture.
        • Comparative neural, behavioral, and social science concerns the common and the specific as well as the complementary conditions under which culture-common mechanisms may be expressed in culture-specific ways.
        • Parenting
          • Mothers, fathers, and others guide the development of infants via direct and indirect effects of their cognitions and practices. Different cultures may dis- tribute infant caregiving responsibilities in different ways,
          • Parents’ cognitions – their ideas, knowledge, values, expectations, goals, attributions, and attitudes – serve many functions.  They generate and shape, mediate the effectiveness of, and organize parenting.
          • Parents who believe that they can or cannot affect their infants’ temperament, intelligence, and so forth tend to modify their parenting accordingly.
          • Parenting cultural knowledge is often conceptualized as naive theories about how infants progress toward culturally idealized social roles, what influ- ences their acquisition of those roles, and how culturally relevant skills are attained
          • culturally distinct parenting cognitions provide parents with a framework for interpreting their infants’ behaviors, guiding parents’ interactions with their infants, and determining the activities and opportunities that parents supply to their infants’ development.
          • Parenting practices relate differentlyto infants’ adjustment depending on the broader cultural context. Jamaican mothers in the UK expect their infants to sit and to walk early, whereas Indian mothers living in the same city in the UK expect their infants to crawl later.
          • Cultural cognitions help to “construct” infancy and parenting. Parents sometimes act on culturally defined cognitions as much or more than on what their senses tell them about their infants.
          • Personality
            • Two general orientations have guided theory and research linking personality to parenting:
            •  One concerns a factor structure thought to compose normal per- sonality, and the other concerns more specific personality characteristics, from anxiety and stress to depression and psychopathology.
            • Another consistent theme among psychoanalytic theorists is that, if parents’ emotional needs are not met during the course of their own development, then their own psychological makeup would reflect in their parenting
            • The Big Five were found to relate differently to diverse parenting cognitions and practices in different cultures.
        • Infancy
          • vacuum. In infancy, we learn how to make sense of and understand objects in the world, develop rudiments of our personality, form our first social bonds, and first learn to express and read basic human emotions.
          • as they develop, infants profoundly change their ecologies and the people in them, just as they are changed by their ecologies and those people
          • mechanisms and processes detailed above, culture shapes parents and parents shape their infants. Infants in different cultures quickly learn to behave in culturally sanctioned ways and come to adhere to culturally endorsed values.
          • These processes take hold early in the life of the infant and operate at all levels of development.
          • Packer and Cole (2015) recount the telling example of infant cultural entrainment in terms contrasting patterns of sleep in the months following birth in rural Kenyan (Kipsigis) and US American urban-dwelling children.
          • Attachment theory, for example, posits that “internal working models” of people in the child’s life emerge from the nature of parent–infant interactions,
          • Policy implications
            • One implication of the increasingly sophisticated view of the origins and conduct of parenting is that many determinants of parenting cognitions and practices are modifiable; thus, what we learn about parenting holds the promise of far-reaching practical implications.
            • Interventions to promote positive parenting have been touted to offer positive outcomes for infants, but they often consume substantial resources and require rigorous appraisal.
            • Vulnerable young are too commonly the victims of parenting that is neglectful or abusive. Infant cries draw a parent’s solicitude but also trigger shaken baby syndrome.
            • industrialization, urbanization, poverty, increasing population growth and density, and especially widespread dual-parental employment – constitute centrifugal forces on parenting.
            • Cross-cultural study has additional policy implications here because the cognitions and practices of a subculture can diverge from those of the domi- nant culture in type, strength, degree, and pervasiveness.
            • Informed infant watching helps to clarify an infant’s develop- ment in relation to how parents want their infant to behave and what parents want their infants to learn and to accomplish.
            • Parents benefit from knowledge of how infants develop. For example, of three cognitive measures – maternal IQ, education, and specific knowledge of infant rearing and infant development – knowledge uniquely explains age differences in mother–infant emotional relationships
        • Interaction
          • parent and infant activities are characterized by intricate patterns of synchronous interactions and sensitive mutual understandings
          • Infants cry to be fed and changed, and when they wake they “tell” parents they are ready to play and to learn. In consequence, sometimes parents’ initiatives are proactive;
          • Conversational turn-taking (which is what mutually contingent vocal exchanges are) is requisite for successful verbal communication and serves as a basis for the acquisition of language and social interaction
          • “To our knowledge, no culture or group has been found in which the fundamental features of turn-taking are absent.”
          • Maternal vocalizations to infants in all cultural communities were contingent on the offsets of infants’ vocalizations overall and in every community.
          • Proximal contexts include situation and demand, family structure and system, support  networks, employment status, and neighborhood residence; social group contexts include SES, religion, ethnicity, and culture; and distal contexts include ecology, history, and even evolution.
          • Human beings acquire understandings of what it is to parent simply by liv- ing in a culture: Generational, social, and media images of parenting, infants, and family life  play significant roles in help- ing people form their parenting cognitions and guide
          • Similarities
            • many adult responses to infants are culturally common, such as the special vocal register of infant-directed speech  whose characteristics vary from adult-directed speech along prosodic, simplicity, redundancy, lexical, and content dimensions.
            • The long evolutionary history of altricial human infant dependency on requisite adult caregiving suggests that some mechanisms associated with adult attentiveness and responsiveness to infants ought to be automatic and deeply ingrained in caregivers’ nervous systems
            • Adults already know (or think they know) something about parenting by the time they first become parents that is, some characteristics of parenting may be “wired” into the biological makeup of the human species
            • The expression of parenting has been linked to hormones, some of which are homologous in females and males  
            • In animals, primiparous females are attracted to infants and care for them, whereas virgins typically avoid or reject infants, suggesting that hormonal events involved in parturition prime the brain to be sensitive to a new and unique set of stimuli
            • Both Italians and Japanese showed significant physiological activation  to both in-group and out-group infant faces. Arousal responses to infants are mediated by the autonomic nervous system.
            • parent. To parent well, a parent’s own needs must be met. When women are inadequately nourished, for example, their health and social development may be compromised, and their abilities to bear and rear healthy infants are jeopar- dized.
          • Differences
            • particularly the help and advice about infant rearing provided to Argentine mothers. By contrast, Belgian mothers rated themselves as relatively satisfied with their parenting, which might be expected in light of the strong infant care supports provided to parents in Belgium in terms of periodicals, consultancies, home visits, health care information workshops,
            • example, among European Americans self-esteem is thought to be important to healthy development in infants, but among Taiwanese self-esteem is less important or even thought to foster psychological vulnerabilities.
            • The challenge that confronts cross-cultural developmental scientists is to understand  and represent similarities and differences in and across cultural groups in ways that transcend simplistic dichotomous group comparisons.

Imagens e arquivos do mapa