7 - The Heritability of Individual Differences Flashcards
Cognitive Affective Processing System
(CAPS)
- a theory of personality that emphasises the importance of situational variables and the cognitive qualities of the individual
Five Cognitive-Affective Units:
- Encoding (how information is stored)
- Beliefs (what outcomes an individual expects from their outcomes)
- Goals (life goals and reward for behaviour)
- Affect (how a person reacts emotionally)
- Competencies (general intelligence and abilities)
Argument for CAPS:
- behaviour is not the result of some global personality trait
> behaviour is based on an individual’s perceptions of themselves in a particular situation
Mischel’s Personality Paradox and counterarguments
The observation that a human being’s personality tends to remain the same over time, but their behaviour can change in different contexts and can seemingly be the opposite of their personality
- Personality coefficient is low
- Extraversion’s correlation with behaviour is 0.14
Counterarguments:
- Epstein states that personality researchers have not measured the relationship between traits and behaviour correctly
- Personality coefficient may be as high as 0.52
3 models of gene-environment interaction in children
Passive Model
- behaviour in the child is a result of the child and parent sharing the same genes
Child Effects Model
- genes cause behaviour in a child, which causes a similar behaviour in the parent
> child shouts causing the parent to shout, causing the child to shout
Parent Effects Model
- the behaviour of a child is responded to by the parent, which reinforces that behaviour in the child
> child is being aggressive, causes parent to be aggressive, causes the child to be aggressive
What is meant by the phrase: ‘genetic variance may be epistatic’ ?
Epistatic Variance describes that phenotypic variation is due to the interactions between specific alleles at different gene loci
What is meant by the phrase: ‘genetic variance may be dominant’ ?
Dominant Variance describes that genetic variation (phenotypic variation) is due to the interactions of specific, alternative, alleles that control ONE trait
(at a specific locus)
> dominant vs recessive alleles
How heritable is personality
Twin studies of the Big Five personality traits provide roughly equal broad heritabilities
- around 0.48
Define Genotype and Phenotype
Genotype:
- the internal genetic code or blueprint for constructing and maintaining a living individual
- made up of genes, containing instructions for building proteins in the body
Phenotype:
- the outward manifestation of an individual (personality, look)
What is heritability (h²)?
h² = 2(rMZ - rDZ)
h² is an estimate of the average proportion of variance for any behaviour accounted for by genetic factors, across the population
> an estimation of the phenotypic variance accounted for by genotypic variance
How to assess heritability and the additive assumption
Heritability can be assessed as a proportion of shared variance of a phenotype between biologically related individuals
- the additive assumption suggests that there are only 2 dimensions that determine phenotype:
> the genetic
> the environmental - heritability is estimated in terms of the relative average strength of both dimensions
> Genetics + Environment will always add up to account for 100% of variance
What effects phenotype?
Additive genetic variation (h)
- degree of relationship between two individuals (number of genes in common)
> between 0 and 1
Shared environment (c) - with the family
Residual effects (e) - non-shared environments, developmental accidents, errors of measurement
Does heritability change with environment?
yes
Loehlin et al.’s findings on phenotype and personality dimensions
Comparing adopted children to their biological and adopted parents
- found that there’s a stronger correlation of personality traits between the child and biological parent than adoptive parent
Pederson, Plomin McClearn and Friberg’s findings on twins
There are stronger personality correlations in identical twins reared together than fraternal twins reared together
- suggesting a genetic influence on personality
5 Problems with Behavioural Genetics
- what actually is heritable?
- genetic variance may be dominant or epistatic
> genetic variance is not completely additive - genes change our environment
> Bouchard found that environmental influences shared by twins or siblings only marginally contribute to personality differences
> Braungart et al. found that unique environmental factors have more influence than shared environmental factors
+ thus we may have been underestimating the role of environment - how representative are twins really?
> heritability estimates are normally done on twin studies
> Kamin and Goldberger found that twin studies overestimate the role of genetics
+ environmental twins have more similar environments than fraternal twins
> Stoolmiller found that children are more likely to be adopted into higher Socioeconomic families, which will influence heritability - we don’t mate randomly
> some are attracted by similar traits (some, opposite)
> body height is positively correlated between spouses
> we assume 50% genetic similarity between parent and child, but if parents are genetically similar, this could be higher
Walter Mischel on the marshmallow test
Mischel showed that children who could delay gratification were more successful in later life
> child self control is a predictor of life success
