Evolution of personality traits Flashcards
What is the Darwinian mechanism of Natural Selection?
natural selection is about reducing variation to identify the most adaptive trait for the environment the individual finds themselves in and this characteristic is passed across generations
what do traits indicated?
- fecundity: number of offspring
- Survivorship: live long enough to reproduce
why do traits develop?
as fitness indicators
What is the Darwinian mechanism of sexual selection?
“arises from differences in reproductive success caused by competition for access to mates” (Anderson, 1994)
what is inter-sexual competition?
competition for mates, between the same sex
what is intra-sexual competition?
general competition, can be between the same or different sexes
what is directional selection?
what you favour one extreme phenotype over another
what is stabilising selection?
when you favour the middle ground in between the 2 extremes. Extremes are selected against. Common in stable environments
what is disruptive selection?
when you favour both the extremes at once. graph looks like m
what is genetic heritability?
- proportion of total phenotypic variation in the population that is due to genetic variation (h^2)
- h^2 = Gv / (Gv+Gv): where Gv= genetic varaition and (Gv+Gv) = genetic and environmental variation
- h^2 is based on the idea that G and E are independent. We know this is not true. The gene-environment correlation (Gecorrelation)
- not all genetic variance is transmitted from one generation to the next
Evolution of personality, PDM three possible mehcanisms for the evolution of personality, Penke, Denissen & Miller (2007)
- Selective Neutrality
- Mutation-Selection
- Balancing-Selection
what traits are associated with reproductive success? Alvergne et al., (2010)
- Measures of the Five Factor Model
- Measures of Reproductive Success
- More children and children who live to 5 year
- Ultimate reproductive success = the number of children times the mean survival of children to age 5, given their BMI
- Greater reproductive success in women is linked to average levels of neuroticism
- Higher extraversion in men is linked to greater social status and more children
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How does PDM suggest selection neutrality?
- Fitness neutral mutations build up and lead to increased genetic variation in the trait
- Only affected by genetic drift
Human Populations are too large - Traits do not influence fitness
- Traits affect many fitness outcomes
- Longevity, reproduction etc.
How does PDM explain that mutation-selection balance influence the development of personality traits?
- Natural selection (decreasing trait variance) balances the effects of mutation (increasing trait variance)
- more susceptible to ‘inbreeding depression’ and ‘out-breeding elevation’ not the case for personality
- traits should be sexually attractive and show assortative mating
How personality is chosen in relationships, Buss and Barnes (1986)
- Husbands who wanted kind-considerate wives got one with high agreeableness and extraversion
- Wives who wanted kind-considerate husbands got ones who were aloof, submissive, unmasculine, unsociable and unamusing
How does PDM describe balancing selection to influence personality trait development
- Extremes of a trait are favoured to the same degree by different environments
- Environmental Heterogeneity: Fitness varies across time and space, and are on average neutral across all spatio-temporal contexts
- Frequency-Dependent Selection: Positive = favours traits with high frequency – runaway selection. Negative = favours traits with a low frequency
Trade off models: cost and benefits (Nettle, 2006)
- Variable Optima: Any traits will have a optimum fitness that varies across situations and time
- Environmental heterogeneity As environment changes then associations between trait and behaviour change
- Implication: The adaptability of a trait will therefore depend on context
what is the trade-off models: Cost and Benefits (Nettle, 2006)
- a summary of hypothesised benefits and costs of increasing levels of each of the big 5 personality dimensions
what are the benefits and costs of extraversion?
benefits:
- mating success
- social allies’ exploration of environment
costs
- physical risks
- family stability
what are the benefits and costs of neuroticism?
benefits:
- vigilance to dangers
- striving and competitiveness
costs:
- stress and depression, with interpersonal and health consequences
what are the benefits and costs of openness
beneifts:
- creativity, with effect on attractiveness
costs:
- unusual beliefs
- psychosis
what are the benefits and costs of conscientiousness?
benefits:
- attention to long-term fitness benefits
- life expectancy and desirable social qualities
costs:
- missing of immediate fitness gains
- obsessionally
- ridity
what are the benefits and costs of agreeableness?
benefits:
- attention to mental states of others
- harmonious interpersonal relationships
- valued coalitional partner
costs:
- subject to social cheating
- failure to maximise selfish advantage
what are behavioural genetics?
- All traits are polygenic (affected by multiple mutations at multiple sites)
- These are termed quantitative trait loci (QTL)
- Twin Studies (MZ, DZ) are used to estimate the degree of genetic and environmental influence on a trait
what assumptions are made in twin studies?
- MZ = Mono-zygotic (identical twins) and DZ = dizygotic (non-identical twins)
- MZ and DZ share the same environment
MZ treated by parents as more ‘equal’ This may be questioned - Gene-environment correlation is minimal. That is, the genetic make up of an individual influences the types of environment they select to be in. Individuals select themselves into certain environments
- Twin scores equivalent to trait scores in the population
- Mating occurs at random
Choose similar people – this increases the DZ correlation relative to the MZ correlation and over estimates the effects of E - Zygosity; How do you assess if twins are identical or not a long time after birth
concordance for common behavioural disorder
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concordance for common behavioural disorder
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h2 and Gene Wide Association (GWAS)
- Higher h2 heritability does not mean that it is easier to find genes associated with the trait
- Height has a heritability (h2 ) of .90
- GWAS find 54 genes for height, these not the same genes across all studies and account for 5% of the variance
what are behavioural reaction norms?
- Designed to examine how people change in their expression of behaviour as the environments they are in change.
- A person high in extraversion will be quite in a library, but probably less so than a person who is more of an introvert.
- A more introverted person will be more outgoing at a party, than they are on average but probably less so than a more extraverted person.
what is personality?
defined in a BRN as the average behavioural response across contexts. This is how personality is traditional defined (average response) what traditional personality measures are supposed to tap into.
what is behavioural plasticity?
represents the flexible expression of the trait. That is, it is acknowledge that people have an average response but that they can vary their behaviour depending ion context
what are behavioural reactions to norms?
- individual plasticity: The trait
(phenotype) changes
as context changes - No Individual Plasticity, just vary in mean level. Some people score higher than others on the trait but no-one shows cross context change
- Everyone one varies across
Context, but some people score higher than others on the trait - Variation in mean
And plasticity
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what is the fleeson and the density distribution approach?
- Density Distribution Approach: Traits reflect ‘accumulation of everyday personality states’: Personality
- Describe the distribution of an individual traits and dynamic interaction with context (contingencies): Behavioural Plasticity
what is Experience Sampling Methodology (ESM)?
- Use experience sampling methods (ESM). Looking at the natural history of behaviour.
- Assess people at multiple time point (4-8 times a day)
Finding 1: behavioural plasticity
Individuals vary as much from moment to moment (with variation) as they do between each other (between variation)
Finding 2 & 3: Personality
- Individual have a central tendency (mean) and these are very stable (correlation of .80 and .90)
- There is also stability in the amount of variability (.50) – therefor variation is fairly stable and a part of personality to be studied
- Tendency to differ with respect to average behaviours.
- Extraverts are moderately extraverted 5-10% more than introverts.
- Personality Traits predict mean (average) and extreme behaviour
what does the socio-economic model imply? (Roberts and Jackson, 2008)
This implies that both the expression of behaviours associated with trait and the mean level of the trait can vary as a function of (1) the influence of the environment via biological factors (route A) and (2) the dynamic interaction of environment, states (emotions, values, beliefs), biology and the trait. (route B)
Miller and Todd’s (1998) two-stage Lens Model
- This model identifies 4 cues we may use to identify a good mate.
- Personality and intelligence are two key parameters we use
- Thus certain traits may survive as they are the basis of selecting a long term mate.
- This implies that the preference for the trait and the trait itself are
heritable
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Iredale et al. (2008)
- Participant plays a number of
economic games and indicates
how much they would donate
to charity. - Play on their own or in dyads watched by someone of the same or opposite sex.
- found men donate more when they are observed by a female
what is cost signalling theory?
- Hard to fake indicators of an animals fitness
- Costly signals offers a solution to the problem of cheating/lying/faking
- ‘If I can fake a signal of fitness, but don’t have to waste the costs of developing it, then I can get more sexual partners’
- The signal has to be high cost, so that only healthy, high status, high condition animals are able to produce and maintain it. Therefore, it is a reliable indicator of evolutionary fitness.
Preference and trait expression should show a genetic correlation?
- Preference for a trait (e.g., openness) and the trait itself should not only be correlated in terms of responses but also at a genetic on level.
- Both variation in the preference for the trait and the trait itself have to pass onto the next generation
