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
SEE GRAPHS IN ONENOTE
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