Evolution and Personality

1. Evolution and Personality

2. Personality? • Behavioral strategy, a tendency to respond in specific ways to particular circumstances (some level of consistency) • Psychological trait vs. psychological state

3. Person/situation debate (Mischel) • Whether person’s behavior is driven by personality or specifics of a situation?

6. Evolutionary persp. • behavior = evolutionary strategy to maximize inclusive fitness • differences in personality = different life strategies • also situationally contingent

7. Personality tests • Tests help measure and define different psychological traits • Factor analysis  personality factor

8. Eysenck – three factors • Extraversion vs. introversion • Neuroticism vs. stability • Psychoticism vs. socialized • Given a score on each dimension. ..never one or the other • Each dimension orthogonal to each other

10. Big five personality factors (Ocean) • Openness to experience • Conscientiousness • Extraversion • Agreeableness • Neuroticism

11. David Buss • Big five factors represent a more evolutionarily plausible way of dividing up human nature • Scoring high/low doesn’t imply +/- of the personality factor • There’s no way of knowing how a person will react in a situation until you know their scores on all relevant factors

13. Nature vs. Nurture? • Many personality factors are to some extent heritable (0.3-0.5 on a scale from 0-1) • Must be a benefit (in terms of inclusive fitness) to having variability in our offspring

14. - Environmental factors • How you were treated as a child, pregnancy – toxins, drugs, radiation, diseases, diet/lifestyle etc., birth trauma, or any good/bad experiences

15. Genetic factors • Differential susceptibility to rearing influence • Search for genetic underpinnings of personality – • D4DR- dopamine receptor (motivation and arousal) • 5HTT – codes for serotonin activity • Genes interact in complex ways so hard to disentangle effects of different genes, predisposition from genes may not be as strong as we think, and early environments may lessen/reverse the effects, heritability in twin studies vary based on different personality traits ( agreeableness and extraversion less heritable than anxiety), genes are pleiotropic

17. Question... • If selection pressures led to the evolution of human nature… Then: shouldn’t we all have the same personality (not including brain damage and other unforeseen circumstances?)

18. Individual differences make little difference in terms of inclusive fitness – and are therefore invisible to natural selection • No single globally optimal human nature

20. Heritable traits • Passed down for a reason- should be fitness enhancing • So why is personality left more to environmental chance than genes? Why is it not completely inherited? • Work by David Buss explains heritable and nonheritable variation in personality depending on whether or not the variation is adaptive (is beneficial for fitness), non-adaptive (no effect on fitness) or is maladaptive (negative fitness consequences)

21. Heritable component of individual differences • Non adaptive variation due to sexual recombination • Some individual differences might be a side effect of sexual reproduction, recombination/interaction among genes rather than natural selection.

23. Heritable component of individual differences • Adaptive variation as a result of changing environments • Environmental changes could have led to evolution. Hard times favor more cooperative people and good times more independent people • As environments change, corresponding personality traits gain a fitness advantage and increase in that population

25. Heritable component of individual differences • Variation in personality as a non-adaptive side effect • Heritable variation in personality may be a side effect of some other factors that are beneficial • Many reasons for differences in personality in offspring:

27. Heritable component of individual differences • Adaptive variation due to ecological niches • In a group, its beneficial to have different personalities so you can form a behavioral niche with less competition from others of similar personalities • …does this explain why psychopaths exist?

29. Heritable component of individual differences • Adaptive variation due to frequency dependency • Successfulness of a personality type depends on strategies adopted by other members of the population • Going to work early to avoid morning rush, driving in a specific lane, Primary psychopaths

31. Non-heritable component of individual differences • Non adaptive differences due to social learning • Skinner behavior learned from reward and punishment • Bandura- learn personality by observing others via social learning (non-genetic influences support this idea)

33. Non-heritable component of individual differences • Non adaptive variation due to chance • With 150 mil synaptic connections and 32,000 genes it’s impossible for the genes to be fully responsible for wiring of the entire brain – this is where the environment comes in. • Ex) different numbers of bristles in fruit flies, life expectancy of roundworms, and more connections in the brains of mice in enriched environments

35. Non-heritable component of individual differences • Adaptive variation due to early environmental calibration (weather forecasting) • Genes may specify psychological mechanisms capable of calibrating a personality to best fit the environment in which the individual develops by attending to local conditions • Phenotype switching • Humans • Early experiences  different reproductive strategies. • Attachment theory is another one

37. Non-heritable component of individual differences • Secondary psychopathy as a gene environment interaction • become the way they are due to the environment – made not born – phenotype based on best guess prediction of future or selected from a battery of alternatives, or calibrated based on early environment • Few opportunities to gain resources by cooperating, dense population (more opportunities to cheat), potential for anonymous interactions (to get away with cheating) etc.

39. Non-heritable component of individual differences • Adaptive Niche filling - Children’s personalities affected by the availability of particular niches in their group • Harris: Leader position taken in the group of friends – you can compete for it or become the joker etc. • Sulloway: First bornsand second borns personality differences

41. Evolution and personality • Soccer team – having differences in roles enhances team as well as the individuals of the group – variation leads to a wait and see strategy to construct the best behavioral phenotype • Malleability/developmental plasticity allows us to alter our strategies in order to exploit circumstances in while we grow up

43. .The end.