Lecture 10
Slides in this set (11)
-
Biological Basis of Personality
- Where
- do personality traits come from?
- Two kinds of influence:
- Environmental:
- Shared
- environments - the family (shared and non-shared)
- Non-shared
- environments – include peers and school
- Biological:
- Evolutionary
- Theory of Personality.
- Genetics
- and personality
- Temperament
- and Personality.
- ---Hans Eysenck - The Ascending Reticular Activating
- System (ARAS).
- ---Gray’s and Cloninger’s
- biological models of personality
- Brain
- anatomy, biochemistry and personality
- Criticism
- of
- western thinking….not linked to the
- physical understanding
- of being human.
- Separation
- between mind and body.
- Variation
- in our biology's
- might
- be where the differences lie.
- Only
- in last 20 years
- has this been looked at more closely. …
-
- Does not represent one cohesive,, theoretical approach.
- Collection of approaches.
- These approaches seek out of origin of human personality and behaviour, looking for links between personality and biology.
- Three main areas:
- Evolutionary theory- personality
- dispositions arise from our evolutionary history and biological makeup
- (temperament) .
- Genetics and personality- how
- much of personality is genetically determined.
- Biological theories, brain anatomy and biochemistry- .personality
- dispositions are the product of a complex biological system.
-
Evolutionary theory and personality
- Provides theoretical platform that underlies human personality.
- Genotype: genetic makeup of individual. At birth, everyone starts with a unique
- genotype; some inbuilt instincts, a temperament and a pre-wired capacity to
- learn certain kinds of behaviours.
- Phenotype: an individual’s observable appearance and
- behaviour that arises out of the interaction of their genotype with the
- environment.
- Biological, environmental,
- behavioural and social shaping processes interact
- with the individual's genotype and create the unique psychological
- characteristics of the individual.
- Focus not on individuals but on patterns of behaviour common to all- 'human behaviour'
- Basic assumptions:
- certain behaviours exist due to evolutionary history of human species-helpful/necessary for survival
- the more a behaviour helps us survive and reproduce, more likely it is to occur in subsequent generations.
- Differences observed, can be understood a consequence of process of evolution throwing up personality variations- most adaptive of which survive and procreate.
- Different personalities may be adaptive in different ways.
-
Evolutionary theory and the five-factor model of personality
- David Buss- well known theorist (1991) - framework for understanding central concepts of (5 factor model) personality in three was:
- Providing understanding of major goals of humans,
- Describing psychological mechanisms and strategies that exist for reaching the goals and overcoming obstacles.
- Identifying individual differences in behaviours that humans use to reach such goals and to overcome obstacles to these goals.
- This model describes main dimensions of behaviour humans need to develop/adapt to environment, and to achieve their primary goals of survival and reproduction.
- This models has been investigated various species: including
- chimpanzees, cheetahs, hyenas, dogs, cats, pigs, guppies, octopuses and
- rhinoceros (Gosling & John, 1999; Gosling, 2001)
- Extraversion,
- neuroticism and agreeableness are found in most studies,
- Openness
- is found in the large minority of studies (chimpanzees exhibited openness and
- monkeys, hyenas and pigs showed curiosity).
- Conscientiousness is only found among chimpanzees.
- Core personality dimensions found amongst animals similar to five factor model (Gosling & John, 1999)
-
Evolutionary theory and personality
- Evolutionary theory provides useful framework/heuristic (set of rules and principles) which link effects of biology and environment
- to
- understand common variability (personality dimensions) in human behaviour
- (Buss, 1991).
- But....
- useful for explaining general personality traits, does not account for individual differences in behaviour.
- Many behavioural and personality
- phenomena may be the result of humans flexibly responding to circumstances,
- particularly the social structure, rather than evolutionary processes.
- Evolutionary theorists are speculating
- backwards across a number of generations. Such speculations cannot be directly
- empirically tested.
- Ideas about the nature and use of
- society’s goals to ensure the survival and reproduction of the species are
- difficult to test.
-
- Behavioural
- geneticists examine
- degree
- to which variation in the phenotype (observable traits of a
- person) can be attributed to variation in the genotype (underlying genetic
- structure) - ‘trait genetics’.
- Controversial - historical association
- with the eugenic movement and a more recent association with the idea of
- cloning.
- About
- 99% of human genes are identical from one individual to another. Behavioural
- genetics concentrates on the approximate 1% of genes that do vary.
- basic methodology
- is to compare similarities and differences in personality between populations
- of individuals who are and are not genetically related.
- Behavioural geneticists employ three
- primary research methods: family studies, studies, twin studies and adoption
- studies (Plomin,
- 2004).
- Basic
- assumption
- of behavioural genetics:
- personality traits
- are influenced by genes:
- -Traits more
- highly correlated across closer genetic relatives than across more distant
- genetic relatives.
- -Traits ought to be more highly correlated
- across pairs of identical monozygotic twins (MZ) who share 100% of their genes
- than across pairs of fraternal dizygotic twins (DZ) who share 50% of their
- genes.
- -Adoption studies – no genetic
- heritability between adoptive parents and their children.
- A
- statistic called the heritability coefficient is computed to reflect the
- genetic influence on traits.
- -Twin studies - heritability estimates for
- most personality traits are around 40-50%.
- -Non-twin studies/adoption studies -
- heritability estimates for most traits are around 20-30%.
- -Most
- likely explanation of difference
- is that effects
- of genes are interactive and multiplicative rather than additive.
-
- Numerous large twin studies
- taken place/ still taking
- place using data from twin registries in various countries.
- examples include:
- 12,898 adult twin pairs in Sweden (Floderus-Myrhed et al., 1980)
- 7,144 adult twin pairs in Finland (Rose
- et al., 1988)
- nompared DZ and MZ twins - evidence for a
- genetic component for extraversion-introversion (around 40-50%).
- Pederson et. al, (1988) also used a twin
- sample but included 95 MZ and 220 DZ twins reared apart. Also found strong
- genetic component for extraversion-introversion.
- Loehlin
- (1989) summarises results across studies for Eysenck’s measures of extraversion
- and neuroticism.
-
Heritability of the ‘Big Five’ and the ‘Big Three’ personality factors
- Several studies have compared the
- correlations between MZ twins and DZ twins for the five factor (e.g., Riemann
- et al., 1997) and three factor (e.g., Loehlin,
- 1989) models of personality.
- If MZ twins are more similar than
- DZ twins this is taken as evidence of heritability.
- ----Typically
- correlations between MZ twins for the five factors of personality are much
- larger than the correlations for DZ twins.
- ----Heritability
- estimates are derived by doubling the difference in correlations between MZ and
- DZ twins.
-
- Caption: Big varaiations, take one from other then multiply N.b. openess didn’t correalte with any part brain activity…
-
- Caption: More studies, multiple genes involved
- Heritability estimates for the ‘Big Five’
- and the ‘Big Three’ personality factors
- -Overall, findings from many studies, twin and
- adoption, indicate:
- ---Personality influenced by genetic factors.
- ---There is a moderate heritability of
- personality from genetic factors, accounting for between 20 and 50 per cent of
- phenotypic variance (e.g., Saudino & Plomin (1996).
- ---Some studies indicate that genetic
- factors may explain as much as 40 – 50% of the variance in the main personality
- trait dimensions.
- Don’t
- know how it is linked but it is, the mind is an enigma still…
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- social/personality Slide Set on Lecture 10, created by Rebecca Phillips on 24/10/2016.
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- Rebecca Phillips
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