Genetics and evolution of personality traits Flashcards
(75 cards)
1
Q
What are the main properties of traits?
A
- normally distributed (between individuals)
- heritable (if fixed via natural selection as a universal, heritability should be 0)
- intra-individual stability (does trait expression differ day to day?)
- inter-individual difference (universal = minimal variability, but people differ)
- inter-correlated, e.g. extraversion and openness to new experiences.
2
Q
What are the two main Darwinian mechanisms driving evolution?
A
Natural and sexual selection.
3
Q
What does natural selection involve for traits?
A
- variation - population property, discretely and continuously varying traits
- differential reproduction of resulting phenotype
4
Q
What two factors determine fitness?
A
Survivorship and fecundity (no. of offspring).
5
Q
What are the three causes of genetic variation?
A
- mutation
- sexual recombination
- gene flow (moving to a new population)
6
Q
What are the two kinds of sexual selection?
A
- inter-sexual (mate selection)
* intra-sexual (competition)
7
Q
What are the different types of genetic mutation which can occur?
A
- copy number variation (CNV) - repetition of segments due to replication/duplication errors.
- single nucleotide polymorphism (SNP) - replication errors via base pair substitution
- translocations or inversions - re-arrangements of large chromosomal regions
8
Q
Define mutation-rate.
A
The speed at which new mutations enter the functional genome.
9
Q
What is the mutation-rate in humans?
A
1.67 per individual per generation, about 1 in 5 born without a new mutation.
10
Q
What is the mutation load?
A
Mildly harmful recessive mutations - each human has about 500.
11
Q
What are the three modes of selection?
A
Directional, stabilising, and disruptive.
12
Q
What does directional selection involve?
A
Individuals low on the trait value scale have low fitness and are selected against, causing the whole normal distribution curve to shift to the right.
13
Q
What are some examples of directional selection?
A
Evolution of IQ and Darwin’s Finches’ bills.
14
Q
What does stabilising selection involve?
A
Individuals who are low and high on the trait value scale have low fitness and are selected against, causing the variation and sd of the normal curve to decrease.
15
Q
What environments is stabilising selection common in, and give an example.
A
Stable environments, sickle cell anaemia - 2 recessive or two dominant not adaptive, one recessive one dominant increases survivorship.
16
Q
What does disruptive selection involve?
A
Individuals in the centre of the trait value scale are selected against, causing a dip around the mean of the curve.
17
Q
When is disruptive selection seen?
A
In speciation.
18
Q
Define heritability.
A
The proportion of total phenotypic variation in the population that is due to genetic variation (h^2).
19
Q
What have psychological tests found regarding heritability?
A
Heritability increases with aggregated measures, reliable measures, and where there is variation.
20
Q
Define psychometrics.
A
The construction and application of psychological tests; mental measurement.
21
Q
What genetic variance is and is not transmitted from one generation to the next?
A
Is: additive effects
Isn’t: dominance and epistasis.
22
Q
Define dominance.
A
The interaction of alleles at the same locus of a chromosome.
23
Q
Define epistasis.
A
The interaction of alleles at different loci of a chromosome.
24
Q
What should natural selection favour?
A
A single best adapted phenotype for optimal species fitness, e.g. eyes.
25
What mechanisms were suggested by Penke, Denissen and Miller (2007) for the evolution of personality?
Selective neutrality, mutation-selection, and balancing-selection.
26
How does selective neutrality work?
* Fitness neutral mutations build up and lead to increased genetic variation in the trait.
* only affected by genetic drift, as natural selection is blind to it.
* traits don't affect fitness
* genetic variation would be additive, however most traits show non-additive effects.
27
How does mutation-selection-balance work?
* natural selection balances the effects of mutation in terms of trait variance
* additive variation increases with trait fitness, but this is most selected genetic component.
* more susceptible to 'inbreeding depression' and 'outbreeding elevation' (e.g. IQ), which is not the case for personality.
* traits should be sexually attractive and show assortative mating, which is not the case for personality.
28
Define polymorphism.
The existence of more than one type of allele at a chromosomal locus which determines phenotype.
29
How does balancing-selection work?
• extremes of a trait are favoured to the same degree by different environmental contingencies.
• overdominance - individuals with heterozygous pairs are fitter than homozygous pairs.
• antagonistic pleiotropy - polymorphism has a positive effect on one trait and a negative effect on another.
• environmental heterogeneity - fitness varies across time and space and is on average neutral across contexts.
• frequency-dependent selection:
- positive = favours traits with high frequency (runaway selection)
- negative = favours traits with a low frequency
30
What trade-off model was proposed by Nettle in 2006?
The cost and benefits model.
31
What are the main premises of the cost and benefits model?
* variable optima - any trait has an optimum fitness function (optima) that varies across situations and time. High and low levels of traits have costs and benefits.
* environmental heterogeneity - as environment changes, so does the association between trait and behaviour.
32
What was suggested by Gangstad (2010), Bouchard and Loehlin (2001) and McDonald (1995) regarding stabilising selection?
Bodily Functional Asymmetry - right-left body asymmetry reflects developmental instability (mutation) and is heritable and negatively related to IQ. Has a quadratic link to personality, suggesting that CNV (copy number variation) may be key to human personality variability.
33
What is the quadratic trait effect of functional asymmetry?
Trait score (x) and FA (y) form a quadratic graph - very high/low trait score = high FA.
34
Define polygenic.
A trait affected by multiple mutations at multiple sites, called Quantitative Trait Loci (QTL).
35
Are all traits polygenic?
Yes.
36
What is assessed in twin studies?
Genetic variance (Vg), by taking DZr from MZr, if Vn and Vs are the same.
37
What assumptions do twin studies make?
* that both mz and dz twins share their environment. However this can be questioned as mz twins may share more.
* gene-environment correlation is minimal (however individuals select themselves into certain environments.
* twin scores are equivalent to scores in the population.
* mating occurs at random (however we choose similar people, increasing the DZ correlation relative to the MZ correlation and causing an overestimate of E).
* zygosity
38
What are the different multivariate models of genetic variation?
Cholesky decomposition, independent pathways, and common pathway.
39
Describe the cholesky decomposition model of genetic variation.
Independent genetic and environmental factors cause certain characteristics, although these may overlap, for example the genetic/environmental cause of being lively may also lead to the individual being talkative.
40
Describe the independent pathways model of genetic variation.
Genetic and environmental factors may cause multiple characteristics which are also caused by other independent genetic and environmental factors.
41
Describe the common pathway model of genetic variation.
Genetic and environmental factors cause a latent factor, which is linked to certain traits also caused by other factors.
42
Which model of genetic variation is preferred?
The common pathway model.
43
What does GWAS stand for?
Gene wide association.
44
Does higher heritability make it easier to find associated genes?
Not necessarily - height has an h^2 of 0.9, but GWAS finds 54 genes accounting for only 5% of the variance.
45
What are the assumptions made by studies using GWAS to study heritability?
* traits in families arise through the same mechanism as in the general population.
* common traits are associated with common genetic variants (rare variants interrupt the stabilising processes)
* heredity occurs via discrete DNA units, independent of development (untrue, sociogenomics)
46
What is meant by nature and nurture, as opposed to nature versus nurture?
Genetic effects only emerge with respect to environmental exposure - behaviours can only be expressed in certain situations.
47
What do the Flynn and Twenge effects state?
That traits (IQ, neuroticism and extraversion) can be inherited across generations, but mean levels differ as environments change.
48
How can h^2 be estimated?
```
h^2= Gv/(Gv+Ev)
Heritability = genetic variation/(genetic variation-environmental variation)
```
49
What is the problem with estimating h^2?
It is based on the idea that genetics and environment are independent, where in fact genetic effects influence environmental exposure.
50
What did Johnson et al. (2011) state?
That "if genetic and shared environmental influences that make family members similar are correlated in ways that affect trait development, estimates of genetic influences are understated... If genetic and nonshared environmental influences that make family members different are correlated, estimates of genetic influences are overstated."
51
According to Johnson et al (2011), what situation leads to underestimating genetic influences?
If genetic and shared environmental influences that make family members similar are correlated in ways that affect trait development.
52
What did Loehlin (2010) investigate?
The role of the environmental (E) factor.
53
What environmental factors did Loehlin (2010) claim affect the behaviour genetics of personality?
GE correlations, c^2, e^2, GE interaction, and evolution.
54
What are the types of GE correlations?
Passive, evocative and active.
55
Define c^2.
The environment shared by family members.
56
What are the types of pre- and post-natal c^2s?
```
Pre = uterus and chorion
Post = extrafamilial (peers, neighbourhood, school), age, sex, siblings as environment, parent-child.
```
57
Define e^2.
Environment unshared by family members.
58
What are the types of e^2s?
Postnatal experience, chance prenatal events, temporal fluctuations in traits.
59
What are the types of genotype-environmental interactions?
Prenatal and postnatal (measured and unspecified E).
60
Define reaction norms.
How genotypes are translated into phenotypes (behaviour) depending on context.
61
How is the role of the environment in trait expression assessed?
* endophenotypes - phenotypic structures that mediate between genes and complex behaviour (nts)
* questionnaires - assess behaviour reactions to specific fitness-relevant contexts as motivational reaction norms.
62
How is personality defined in a behavioural reaction norm (BRN)?
The average behaviour response across contexts.
63
What is behavioural plasticity in terms of behavioural reaction norms?
The flexible expression of a trait.
64
What does Fleeson's Density Distribution Approach state regarding traits?
They reflect 'accumulation of everyday personality states' - describe the distribution of an individual trait and add dynamic interaction with context (contingencies).
65
What does Fleeson's Density Distribution Approach involve?
Defining central tendency, variability, skew, min/max etc.
66
What is Experience Sampling Methodology?
Assessing people at multiple time points (4-8 times/day) to measure their experience at a particular time.
67
In what three ways can time intervals for ESM be chosen?
* event contingent - when a key event occurs
* interval contingent - after pre-set interval
* signal contingent - when signalled, e.g. with a beeper.
68
What three things has ESM found?
1. Individuals vary as much from moment to moment (within subj variation) as they do between subjects (Fleeson, 2004). Potential for plasticity (behavioural reaction norm).
2. Individuals have a very stable central tendency (correlation of 0.8-0.9) - personality (BRN).
3. There is also stability in the amount of variability (0.5) - therefore variation is fairly stable and a part of personality to be studied.
69
What did Fleeson (2007) state regarding trait expression?
Both personality (mean) and variability (sd) of trait expression are situationally contingent. E.g. Friendly situations give rise to more extraverted behaviour.
70
What did Fleeson and Gallagher (2010) state regarding trait expression?
Traits predict mean and extreme trait expression.
71
What does the Socio-Genomic Model (Roberts and Jackson, 2008) state?
Genes affect behaviour, are conserved across species, and interact dynamically with the environment. E.g. Wrasse fish - females turn into males.
72
What did Jackson et al. (2012) find about the relationship between agreeableness and time for civilian and military service groups?
Civilian agreeableness increased over time, military didn't.
73
How do SSRIs influence personality?
Decrease neuroticism score and increase extraversion score.
74
How did Ferguson, Heckman and Corr (2011) integrate biology, ecology, psychology and economics in their theory?
* personality traits evolved to have relative costs and benefits. Traits influence the probability of expressed behaviour dependent on context.
* external investment can change mean level on traits or via context, states and biology.
* traits are not deterministic
75
What did Ferguson, Heckman and Corr (2011) state regarding BRNs?
BRNs offer a useful single framework - active external investment or changes in biological systems and the influence of thoughts, feelings and behaviours may result in changes to the mean level of a trait (personality) or expressed behaviour (plasticity). Traits are not deterministic.
