The Genetics and Evolution of personality traits

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What is evolution about?
Selecting the most adaptive traits, we all have two eyes as this is the most adaptive fit to our environment
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What do we need to explain?
Why traits like extraversion, neuroticism etc, remain in the population. What is there adaptive function
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What do we need to explain?
why traits show a range of scores - some people are more or less extravert than others
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What is the first theory of Darwin?
Natural selection
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What is natural selection?
It is about reducing variation to identify the most adaptive trait for the environment the individual finds themselves in and this characteristic is passed on across generations
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What is a trait?
It has fitness which indicates adaptations in terms of two qualities of off spring 1) fecundity (number of offspring 2) and survivership
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Why do traits develop according to natural selection?
Fitness indicators
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What is sexual selection?
Inter-sexual (mate selection), intra-sexual (Competition), are certain traits more desirable as they signal certain qualities
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What is directional selection?
Darwin's finches bills, one variation is most adaptive and is selected for model for evolution of IQ
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What are stabilising selection?
Extremes are selected against, common stable environments, extreme birth weight in babies is selected against
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What is distruptive selection?
Sexual dimorphism
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What is heritability?
Proportion of total phenotypic variation in the population that is due to genetic variation
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What is the equation?
H2 = Genetic variation / Genetic and environmental variation
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What is H2 based on?
The idea that G and E are independent. We know this not to be true. The gene-environment correlation
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Not all genetic variance is what?
Transmitted from one generation to the next
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What effects do they have?
Only addictive effects, dominance (interaction of alleles at same locus of chromosome) and epistasis (interaction of alleles at different loci of chromosome) are not
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What did Penke, Denissen and Miller (2007) suggest?
Three possible mechanism for the evolution of personality, selective neutrality, mutation-selection, balancing selection
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What is selection neutrality?
Fitness neurtral mutations build up and lead to increased genetic variation in the trait, only effected by genetic drift, human populations are too large
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What do traits do not influence?
Fitness, traits effect many fitness outcomes, longevity, reproduction
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Are there any traits that maybe associated with reproductive success?
Examined in rural senegal by Alvergne et al (2010)
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What is it measured of?
Five factor model, measures of reproductive success
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What are the 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
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Alvergne et al, 2010
Greater reproductive success in women is linked to average levels of neuroticism
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What is higher extroversion linked to?
In men it is linked to greater social status and mroe children
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What is mutation-selection-balance?
Natural selection balances the effects of mutation, more susceptible to inbreeding depression and out breeding elevation, not the case for personality
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What should traits be?
Sexuall attractive and show assortative mating
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Is there any evidence for assortative mating?
Yes but only for personality traits of O and C, husbands who wanted kind considerate wives got one with high A and E
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What did wives who wanted kind considerate husband got what?
Aloof, submissive, unmasculine, unsociable and unamusing (Buss Barnes, 1986)
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What is balancing selection?
Extremes of a trait are favoured to the same degree by different environments
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What is environmental heterogeneity?
Fitness varies across time and space and are no average neutral across aptio-temporal contexts
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What is frequency dependent selection?
Positive: favours traits with high frequency - runaway selection, negative: favours traits with a low frequency
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What is variable optima?
Any traits will have an optimum fitness that varies across situations and time
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What is environmental heterogeneity?
As environment changes then associations between trait and behaiour change
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What is the implication?
The adaptability of a trait will therefore depend on context
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What are the benefits and costs of Extraversion
+ Mating success, social allies, exploration of environment, -physical risk and family stability
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What are the benefits and costs of Neuroticism?
Vigilance to dangers; striving and competitiveness - stress ad depression, with interpersonal and health consequences
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Openness
Creativity with effect on attractiveness, unusual beliefs; psychosis
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Conscientiousness
Attention to long term fitness benefits; life expectancy and desirable social qualities, missing of immediate fitness gains;obsessionality, rigidity
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Aggreeableness?
Attention to mental states of others; harmonious interpersonal relationships; valued coalitional partner; subject to social cheating; failure to maximise selfish advantage
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Behavioural genetics
All traits are polygenic (affected by multiple mutations at multiple sites),
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What are these termed/
Quantitative trait loci
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Why are twin studies used?
estimate the degree of genetic and environmental influence on a trait
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What do MZ and DZ do?
Share the same environment, Mz treated by parents as more equal, this may be questioned
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What is the second assumption of twin studies?
Genetic make up of an individual influences the types of environment they select to be in, individuals select themselves into certain environments
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What were the twin scores equivalent to?
Trait scores in the populations
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What occurs at random?
Mating occurs, choose similar people- this increases the DZ correlation relative to the MZ correlation ad over estimates the effects of E
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What is zygosity?
How do you assess if twins are identical or not a long time after birth
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What is the concordance for common medical disorders?
Genetic effect is assessed via the difference between the correlation on the trait between identical (MZ) and non identical (DZ) twins Mzr-DZr. The greater the difference the stronger the genetic effect
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What is the concordance for common behavioural disorders?
Strong concordance in MZ twins for reading disability, major affective disorder, sutism, Alzheimers, SZ, alcoholism
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What is the concordance for personality?
IQ, verbal reasoning, processing speed, scholastic achievement
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What does higher H2 heritability mean?
That it is easier to find genes associated with the trait
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What has height got?
Height has a heritability
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What did GWAS find?
54 genes for height, these not the same genes across all studies and account for 5% of the variance
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When do genetic effects only emerge?
With respect environmental exposure
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For example?
Corn selected for height in one generation will be small in the next if there is little rain fall, traits can be inherited across generation but mean levels differ as environmental change
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What do the genes and environment do?
Interact dynamically, Wrasse fish (females turn into males)
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What is the role of the environmental ?
GE Correlations Passive, Active, Evocative c2 – prenatal Uterus Chorion c2 – postnatal Extrafamilial Age Sex Sibs as environment Parent-Child
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What is the trait expression?
If you score high on extraversion will you always exhibit extraverted behaviours or will you sometime exhibit introverted behaviour
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People should have preferred way to what?
Express thier trait but also be able to express aspects depending on context , people should have preferred way to express their trait but also be able to express aspects depending on context
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What behavioural reaction norms?
DEveloped from ecology, designed to examine how people change in their expression of behaviour as the environments they are in change
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What would a person in high extraversion would be?
Quite in a library, but probably less so than a person who is more of an introvert
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What would an introverted person do?
They will be more outgoing at a party, than they are on average but less than more a more extraverted person
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What is personality?
Defined in a BRN as the average behavioural response across contexts. This is how personality is traditionally defined what traditional personality measures are supposed to tap into
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What is behavioural plasticity?
Represents the flexible expression of the trait. That is it is acknoledge that people have an average response but that they can vary their behaviour depending ion context
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What is individual plasticity?
the trait changes as context changes
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What does everyone varie?
Across the context, but some people score higher than others on the trait
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What is the 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
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What is the phenotype expression/
The mean behaviour, personality typical performance, plasticity, trait expression, potential for adaptability
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What is experience sampling methodology?
use experience sampling methods, looking at the natural history of behaviour, assess people at multiple time point
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What is the first finding?
Behavioural plasticity: individuals vary as much form moment to moment and they do between each other
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Within and between person variability in what?
behaviour and affect
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What is the typical person's behaviour?
Differs as much from occasion to occasion as does his or her emtion, and more than the amount people differ from each on other on average
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What was findings 2&3
Individuals have a central tendency and they are very stable, there is also stability in the amount of variablity therefore variation is fairly stable and a part of personality to be studied
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What does each point in this graph represent?
Average level of extraersion in 2 different weeks. How people act on average in one week is highly similar to how they act on average in another week
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What is the extant that the behaviour is what?
Indicative of the personality trait, tendency to differ with respect to average behaviours, extraverts are moderately extraverted 5-10% more than introverts. Personality traits mean and extreme behaviour
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What does the socio genomic model imply?
Both the expression of behaviours associated with trait and the mean level of the trait can vary as a function
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What is the function of?
The influence of the environment via biological factors and the dynaic interaction of environment, states, biology and the trait
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What is the linear growth model estimates show?
Agreeableness as a function of time of measurement and group and the initial assessment occured during participants final year of high school, prior to conscription and the follow up assessments were completed on average at 2 year intervals
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What is inter-sexual selection?
Mater selection/choice, what traits may a life mate desire
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What is intra-sexual selection?
Dominance hierarchies and aggression
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What does sexually selected traits show?
Variability otherwise choice and competition are not possible, if we were all the same on a trait then who would you choose to be a sexual partner
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What does the two stage model identify?
4 cues we may use to identify a good mate, personality and intelligence are two key parameters
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What traits will survive?
preference for the trait and the trait itself are heritable
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Iredale et al?
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
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What was found?
For men only, when observed by a female they donate more
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What can phenotypes indicate?
Good genes, good partner, good parents, can these be faked?
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What indicates good genes?
Correlate with fitness indicators, low mutation load: High IQ is linked to lower fluctuating bodily asymmetries (mutation load)
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What indicates a good partner?
Show benefits for long term sexual relationships, loyalty, faithful, generous
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What indicates good parents?
Traits for parental care; feeding, protection, conflict resolution in siblings, teaching
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What is the costly singaling theory?
Hard to fake indicators of an animal fitness. Costly signals offers a solution to the problem of lying/cheating/faking
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What is the signal?
It 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.
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What can the costs can be?
Matter, energy, time, risk :Peacock's tail
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What is preference?
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.
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What is both variation in the preference for the trait and what?
The trait itself have to pass onto the next generation
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What do we need to explain?

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Why traits like extraversion, neuroticism etc, remain in the population. What is there adaptive function

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What do we need to explain?

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What is the first theory of Darwin?

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What is natural selection?

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