Perception

Perception

processes that occur in the mind which convert sensations into a representation of the world that we can make sense of.
1. the process by which the brain organises and interprets sensory information
2. cognition - mental processes - all the processes by which... sensory input is transformed,reduced,elaborated, stored,recovered and used (Neisser 1967)
use environment to create perceptions
Deregowski (1972)
1. 3-d perception of pictures
2. people of western cultures tend to see pictures in 3 dimensions
cues
1. important
  1. i.e - depth
    1. judge distances
ability to recognise people
1. Kozlowski an Cutting (1977)
  1. able to show that minimal perceptual info is needed to identify a moving thing as a person
Gibson and Walk (1960) walking off a cliff
1. sample - 36 infants ranging in age from 6 months to 14 months
  1. also tested a variety of animal neonates including lambs, chicks, rats, kittens and turtles
2. visual cliff: shallow side or deep side - thick piece of glass placed over a wooden box. Under the glass is a change of levels.
  1. baby is placed in the middle of the glass and its mother tries to get it to crawl either over the shallow or the deep end
  2. if the babies refuse to crawl over the shallow end but refuse to crawl over the deep end this suggests they have depth perception
    1. if they crawl over the deep end they have no depth perception or they have guessed the experiment/ do not care
3. results
  1. children
    1. 9/36 stayed where they were and did not crawl in either direction. All of the 27 crawlers moved onto the shallow side at least once and only 3 crawled over the deep side
      1. many kids crawled away from the deepside/ cried when their mother tried to encourage them. Some peered through the glass and backed away and others patted the glass however did not cross the cliff
    2. suggests babies can also perceive depth
  2. animals
    1. chicks -24 hours - never went over the cliff, always went to the shallow side
    2. rats went over the deep side as often as the shallow side - however rats tend to use tactile cues when moving around so when the glass was lowered, they close the shallow side 95% time.
    3. turtles only chose the shallow side 76% of the time - however = aquatic creatures and so have less reason to fear depth
    4. suggests animals are able to discriminate depth as soon as they can move around - has obvious survival value
4. also investigated pattern density
  1. patterns of different sizes
  2. rats chose large check but chicks showed no preference - shows some animals require learning (narrow check suggests depth)
  3. motion parallax - made checks appear the same
    1. rats and chicks still avoided the deep side - use this cue from an early age
5. discussion
  1. the most this study says is that babies as young as 6 months old can perceive depth
  2. source et al 1985 - infants who saw the fearful face did not crawl across but infants who saw the happy face looked down at the cliff again and then crossed to their mother
    1. if put on a flat plane with no visual cliff they crawled over without checking with their mother
  3. it is worth noting the practical and ethical implications of the study
    1. 25% of babies did not respond
    2. babies distressed at mothers enticing them over a cliff
6. Nature/Nurture debate Important but stale Maturation Vs Learning Internal Vs External Genetic Vs Environment (determined) (imposed) Nature through Nurture
7. It is very difficult to carry out psychological research at the early stages of development only recently that scientists have taken the view that newborns are not blind and deaf. Kagan (1971)“Nature has apparently equipped the newborn with an initial bias in the processing of experience. He does not, as the 19th C. empiricists believed, have to learn what he should examine.” (p.60) taste, touch and smell are fully functional at birth Newborns can also hear low and mid audible (speech range) frequency sounds Newborns can’t see very well (technically they are blind)
  1. Taste, touch and smell are stimulated in the womb So is audition But it’s like listening to sound in the bath Though the infant is only exposed to low and mid audible frequency range (up to about 6/7000Hz) But what about vision? Very little light (or high frequency sound) gets into the womb so the eyes and the rest of the visual system is underdeveloped
  2. We know that infants have certain in built (innate) mechanisms and “…while infants may not, indeed, see as well as adults do , they normally see well enough to function effectively in their role as infants.” Hainline & Abramov (1992; p40) And visual development requires an interaction between the sensory aspects (colour, movement etc) and the motor system (experience) Remember: It is difficult to measure perception in very young children
  3. Motor (eye muscles) Convergence and divergence (movement of the eye muscles) Accommodation (lens) Binocular (two eyes) Image from both eyes are compared for disparities (e.g., magic eye pics) Monocular E.g. Linear perspective, Familiar size (size constancy, pattern density, Motion parallax, lighting and shade, texture gradient aerial perspective )
walk like a man
1. do we need all the info we take in to recognise people? ie - clothes, face and hair etc
2. can we recognise people from a few simple visual ques? YES!
3. Kozlowski and cutting (1977)
  1. participants - used undergraduates as subjects.
    1. role was to watch videos and identify if male or female
    2. participated in groups and for experiments 1 and 3/5 they were payed
  2. design
    1. comparison of the study is the comparison of the pattern of subjects actual judgements with the pattern that would be seen if they were guessing
    2. the greater proportion of correct responses to incorrect responses means we can be more confident that subjects are doing more than guessing
    3. binomial test used to decide whether the proportion of correct responses is sufficiently high to allow us to conclude that subjects can really identify the sex of the walker
  3. materials and apparatus
    1. video recordings of 6 people (3 male and 3 female)
    2. models walked from left to right and back again in front of the camera wearing reflective tape on their shoulders, elbows, wrists,hips,knees and ankles.
    3. in each experiement the models walked differently and were in different orders.
    4. subjects viewed 10 trials of each of 6 models, randomly pre-recorded on video
    5. write down m or f
      1. 5 point scale to rate how confident they were
  4. results
    1. 5/6 walkers were identified correctly in experiment 1 on the majority of trials (one woman walker was consistently mis-identified as male
    2. overall, subjects made correct judgements on 63% of trials - if the mis-identified female is excluded from the analysis then nearly 69% of judgements were correct
    3. for the trials which participants rated themselves the most confident they averaged 87% correct responses
      1. subjects could tell when they were looking at a male or female
    4. exp 2 - had to identify static people
      1. only 1/20 guessed the lights represented people, most guessing xmas tree lights
    5. 3 and 4 - effect of different styles of walking on judgement
      1. did not have any effect - ie arm swing on judgements apart from making them less confident and more likely to guess
    6. 5 - number and positioning of point light sources were manipulated
      1. upper body cues found to be more effective than lower body cues
      2. more specificr research needed ie guessing se with just ankle lights on
  5. discussion
    1. insight is used to design modern computer graphics
    2. is fastinating
    3. grammar of movement - increased speed =less grammatical
4. can recongise the sex of a person just from the movement of lights attached to their body
5. Form derived from patterns of movement generated by living forms Special form of SFM Present very early (4 mnths) in perceptual development (Fox & McDaniel, 1982; Bertenthal, et al., 1987) However, experience plays a significant role Some living object forms are easier to detect than others Human gait is easier to detect than other animal gait Human figure activity is harder to recognise if inverted Remains unscathed as we age
6. Form Object shape - early stage of identification (area V3) Contours and artificial contours Contours of light boundaries (EDGES) First step to building up a representation of the visual world (Marr, 1980) Form can be implied Structure from motion (SFM) Object form can be perceived from movement Very little information is needed to convey form
sensation
1. initial stimulation of our sensory systems - sight, hearing
perception is in effect, derived from an endless stream of eternal information and influenced by our arousal states and past experiences
1. attention plays a critical role in making sense of our sensations
2. audition (hearing)
  1. the ear
    1. detect sound waves
      1. sounds differ along 3 dimensions - amplitude, freq and compleity
    2. outer ear
      1. compromising of the pinna, the auditory canal and the tympanic membrane
    3. the middle ear
      1. compromising the ossicles - made up of 3 connecting bones (hammer,anvil and stirrup) and the eustachian tube - which helps regulate air pressure
    4. the inner ear
      1. compromising the cochlea
  2. page 86 on taking in sound of essential psychology
3. seeing (visual)
  1. 80% of info comes from visual world
  2. the eye
    1. light enters the eye through the cornea
      1. passes through the pupil and is focused on to the back of the eye (retina) by the lens
    2. the retina contains photoreceptor cells called rods and cones that convert light energy into electrochemical signals
      1. rods - extremely sensitive to movement as they have good temporal resolution but not to colour and they do not carry fine detailed information
      2. cones - responsible for fine detailed vision in colour
      3. bipolar cells -repolarise and hyperpolarise in response to rods and cones
    3. blind spot is where the optic nerve is formed
    4. eye to the brain
      1. page 89 essential psych
sensation - the physical stimulation of the sensory apparatus (effect of light on the retina, vibrations on ear drum, surface pressure on the skin etc)
1. perception - the faculty of percieving - the ability of the mind to refer sensory information to an external object and its cause (OED) - the experimental comonent of sensation
2. 5 senses
  1. vision (sight)
    1. eye -light receptive ganglion on cells in the retina
    2. stimulus - electromagnetic wave forms
  2. audition(hearing)
    1. ear - timpanic membrane (ear drum) irgan of corti and hair cells
    2. changes in air pressure = stimuli
  3. somatory/sensory/haptics (touch)
    1. skin - various mechanoreceptors
    2. stimuli - mechanical pressure/deformations of the skin, changes in temp
  4. gaustation (taste)
    1. tongue - taste buds in papillae
    2. stimulus - chemical substances disolved in saliva
  5. olfaction (smell)
    1. nose - cilia in the mucus layer of the epithelium situated at the top of the nose and back of the throat
    2. stimulus - airbourne substances disovled in the mucus
3. brain bits
  1. primary auditory cortex = hearing
  2. primary sensory cortex = touch
  3. primary visual cortext = vision
  4. amygdala and hypothalamus (taste)
  5. pitruitary gland (smell)
4. recognition
  1. recognising objects - recognition is complex
    1. multi sensory activity
    2. effortless
5. perception is adequate not accurate - multi sensory
6. why does perception match reality? (martin and foley (1992))
  1. physical stimuli are rich in information/ the human sensory system is really good at gathering info/ concepts shape our perception
approaches
1. ecological approach
  1. j.gibson 1950,1965
  2. perception is a direct process
  3. light is rich in info
  4. 4 main principles - the stimulus should not properly be described in terms of the optic array not the retinal image/ perception is not static but active, movement of the observer is crucial for generating info/ key element of optic aray is invariant information
2. constructivism
  1. basic assumption - perception is influenced by top down information
    1. hypothesis and expectations
  2. 3 shared assumptions
    1. active and constructive process - more than sensation
    2. perception = indirect by product of external input (sensation) and hypothesis
    3. influenced by individual factors (personal experience/situation)
  3. gregory 1970,1980,1990 - wiki
    1. external world is full of info but sensoryinput is impoverished. instead sensory input form the basis a best guess about the stimuli and the world
    2. errors and illusions occur because of these best guesses
3. computational approach
  1. david marr's 1982 2.5 dimensional sketch
    1. primarily (not exclusively) a bottom up account mapping perception to the underlying physiology
      1. begins wiith the retinal image and ending with high level representation, attempts to explain how perception is constructed
    2. identified 3 levels of analysis
      1. the computational level - what needs to be figured out
      2. the algorithmic level - how, what needs to be figured out, is figured out
      3. the hardware level - what is it that does the working out
      4. 3 stage process - primal sketch > 2.5 sketch >3d sketch

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	Created by oneill1304 almost 11 years ago