EVOLUTION AND PERSONALITY PERSONALITY v Behavioral strategy a
EVOLUTION AND PERSONALITY
PERSONALITY? v Behavioral strategy, a tendency to respond in specific ways to particular circumstances (some level of consistency) v Psychological trait vs. psychological state
PERSON/SITUATION DEBATE (MISCHEL) v. Whether person’s behavior is driven by personality or specifics of a situation?
EVOLUTIONARY PERSP. vbehavior = evolutionary strategy to maximize inclusive fitness vdifferences in personality = different life strategies valso situationally contingent
PERSONALITY TESTS v. Tests help measure and define different psychological traits v. Factor analysis personality factor
EYSENCK – THREE FACTORS v. Extraversion vs. introversion v. Neuroticism vs. stability v. Psychoticism vs. socialized • Given a score on each dimension. . . never one or the other • Each dimension orthogonal to each other
BIG FIVE PERSONALITY FACTORS (OCEAN) v Openness to experience v Conscientiousness v Extraversion v Agreeableness v Neuroticism
DAVID BUSS v. 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
NATURE VS. NURTURE? v. Many personality factors are to some extent heritable (0. 3 -0. 5 on a scale from 0 -1) v. Must be a benefit (in terms of inclusive fitness) to having variability in our offspring
- ENVIRONMENTAL FACTORS v How you were treated as a child, pregnancy – toxins, drugs, radiation, diseases, diet/lifestyle etc. , birth trauma, or any good/bad experiences
GENETIC FACTORS v Differential susceptibility to rearing influence v Search for genetic underpinnings of personality – • D 4 DR- dopamine receptor (motivation and arousal) • 5 HTT – codes for serotonin activity v 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
QUESTION. . . v. 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? )
v. Individual differences make little difference in terms of inclusive fitness – and are therefore invisible to natural selection v. No single globally optimal human nature
HERITABLE TRAITS v Passed down for a reason- should be fitness enhancing v So why is personality left more to environmental chance than genes? Why is it not completely inherited? v 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)
HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v. 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.
HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v 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
HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v Variation in personality as a non-adaptive side effect v Heritable variation in personality may be a side effect of some other factors that are beneficial v Many reasons for differences in personality in offspring:
HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v Adaptive variation due to ecological niches v In a group, its beneficial to have different personalities so you can form a behavioral niche with less competition from others of similar personalities v …does this explain why psychopaths exist?
HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v. Adaptive variation due to frequency dependency • Successfulness of a personality type depends on strategies adopted by other members of the population v. Going to work early to avoid morning rush, driving in a specific lane, Primary psychopaths
NON-HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v Non adaptive differences due to social learning v Skinner behavior learned from reward and punishment v Bandura- learn personality by observing others via social learning (non-genetic influences support this idea)
NON-HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v Non adaptive variation due to chance v 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. v Ex) different numbers of bristles in fruit flies, life expectancy of roundworms, and more connections in the brains of mice in enriched environments
NON-HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v 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 v Humans • Early experiences different reproductive strategies. • Attachment theory is another one
NON-HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v 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 v Few opportunities to gain resources by cooperating, dense population (more opportunities to cheat), potential for anonymous interactions (to get away with cheating) etc.
NON-HERITABLE COMPONENT OF INDIVIDUAL DIFFERENCES v Adaptive Niche filling - Children’s personalities affected by the availability of particular niches in their group v Harris: Leader position taken in the group of friends – you can compete for it or become the joker etc. v Sulloway: First borns and second borns personality differences
EVOLUTION AND PERSONALITY v. 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 v. Malleability/developmental plasticity allows us to alter our strategies in order to exploit circumstances in while we grow up
. THE END.
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