evolutionary perspectives on personality chapter 8 copyright © 2005 the mcgraw-hill companies, inc....

Evolutionary Evolutionary Perspectives on Perspectives on

PersonalityPersonality

Chapter 8Chapter 8

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


Evolution and Natural Evolution and Natural SelectionSelection

All humans today come from an All humans today come from an unbroken line of ancestors who unbroken line of ancestors who accomplished two tasks: They accomplished two tasks: They survived to reproductive age, and survived to reproductive age, and they reproducedthey reproduced

We carry adaptive mechanisms that We carry adaptive mechanisms that led to our ancestors’ successled to our ancestors’ success


Evolution and Natural Evolution and Natural SelectionSelection

Human nature and human Human nature and human personality made up of a collection personality made up of a collection of evolved mechanismsof evolved mechanisms

Before Darwin, two features of Before Darwin, two features of evolution were recognized: Change evolution were recognized: Change over time and apparent adaptation over time and apparent adaptation to environmentto environment


Natural SelectionNatural Selection

Darwin revolutionized biology by Darwin revolutionized biology by proposing a theory of the process by proposing a theory of the process by which adaptations are created and which adaptations are created and changes take place over time—changes take place over time—natural selectionnatural selection

More offspring produced than can More offspring produced than can survive and reproducesurvive and reproduce



Changes or variants that better Changes or variants that better enabled an organism to survive and enabled an organism to survive and reproduce lead to more descendantsreproduce lead to more descendants

Descendants inherit variants that led Descendants inherit variants that led to their ancestors’ successto their ancestors’ success



Thus, successful variants are selected Thus, successful variants are selected and unsuccessful variants are weeded and unsuccessful variants are weeded outout

Over time, successful variants come Over time, successful variants come to characterize entire speciesto characterize entire species

Adaptations: inherited solutions to Adaptations: inherited solutions to survival and reproductive problems survival and reproductive problems posed by hostile forces of natureposed by hostile forces of nature


Sexual SelectionSexual Selection

Darwin noticed that many mechanisms Darwin noticed that many mechanisms seemed to threaten survival, such as seemed to threaten survival, such as the peacock’s elaborate plumage and the peacock’s elaborate plumage and the stag’s large antlersthe stag’s large antlers

Darwin proposed evolution by sexual Darwin proposed evolution by sexual selection as solution—these traits selection as solution—these traits evolved because they contributed to evolved because they contributed to an individual’s mating successan individual’s mating success


Sexual SelectionSexual Selection

Two forms of sexual selectionTwo forms of sexual selection Intrasexual competitionIntrasexual competition: Members of : Members of

the same sex compete with each other the same sex compete with each other for sexual access to members of the for sexual access to members of the other sexother sex

Intersexual competitionIntersexual competition: Members of : Members of one sex choose a mate based on their one sex choose a mate based on their preferences for particular qualities in preferences for particular qualities in that matethat mate


Genes and Inclusive Genes and Inclusive FitnessFitness

Gene—packet of DNA inherited by Gene—packet of DNA inherited by children from parents; smallest discrete children from parents; smallest discrete unit inherited without being broken upunit inherited without being broken up

Discovery of the gene as a unit of Discovery of the gene as a unit of inheritance led to key discovery, that inheritance led to key discovery, that natural selection and sexual selection natural selection and sexual selection are different forms of the same processare different forms of the same process


Genes and Inclusive Genes and Inclusive FitnessFitness

Differential gene reproduction—Differential gene reproduction—reproductive success relative to othersreproductive success relative to others

Inclusive fitness theory (Hamilton, Inclusive fitness theory (Hamilton, 1964)1964) Inclusive fitness: personal reproductive Inclusive fitness: personal reproductive

success (number of offspring you success (number of offspring you produce) plus effects you have on the produce) plus effects you have on the reproduction of your genetic relatives, reproduction of your genetic relatives, weighted by genetic relatednessweighted by genetic relatedness


Products of the Products of the Evolutionary ProcessEvolutionary Process

AdaptationsAdaptations Byproducts of AdaptationsByproducts of Adaptations Noise or Random VariationNoise or Random Variation


AdaptationsAdaptations

Adaptations are the primary Adaptations are the primary products of selection, defined as products of selection, defined as “reliably developing structure in the “reliably developing structure in the organism which, because it meshes organism which, because it meshes with the recurrent structure of the with the recurrent structure of the world, causes the solution to an world, causes the solution to an adaptive problem”adaptive problem”


AdaptationsAdaptations

Adaptive problem: Anything that Adaptive problem: Anything that impedes survival or reproductionimpedes survival or reproduction

Hallmark of adaptations are special Hallmark of adaptations are special design, including efficiency, design, including efficiency, precision, and reliabilityprecision, and reliability e.g., xenophobia e.g., xenophobia


Byproducts of Byproducts of AdaptationsAdaptations

Byproducts are incidental effects Byproducts are incidental effects of adaptations not properly of adaptations not properly considered to be adaptationsconsidered to be adaptations e.g., color of bonese.g., color of bones


Noise or Random Noise or Random VariationVariation

Neutral with respect to selectionNeutral with respect to selection e.g., shape of the human earlobee.g., shape of the human earlobe


Evolutionary PsychologyEvolutionary Psychology

Premises of Evolutionary Premises of Evolutionary PsychologyPsychology Domain-specificityDomain-specificity: Adaptations : Adaptations

are designed by evolutionary are designed by evolutionary process to solve specialized process to solve specialized adaptive problemsadaptive problems



Premises of Evolutionary Premises of Evolutionary PsychologyPsychology NumerousnessNumerousness: Expectation is that : Expectation is that

there are many psychological there are many psychological adaptations, because different adaptations, because different adaptations are required to solve adaptations are required to solve different adaptive problemsdifferent adaptive problems



Premises of Evolutionary Premises of Evolutionary PsychologyPsychology FunctionalityFunctionality: Psychological : Psychological

adaptations are designed to adaptations are designed to accomplish particular adaptive accomplish particular adaptive goalsgoals


Empirical Testing of Empirical Testing of Evolutionary HypothesesEvolutionary Hypotheses

Hierarchy of levels of analysis in Hierarchy of levels of analysis in evolutionary psychologyevolutionary psychology General evolutionary theoryGeneral evolutionary theory Middle-level evolutionary theoriesMiddle-level evolutionary theories



Hierarchy of levels of analysis in Hierarchy of levels of analysis in evolutionary psychologyevolutionary psychology Specific hypothesesSpecific hypotheses Specific, testable, falsifiable Specific, testable, falsifiable

predictionspredictions



Two modes of conducting empirical Two modes of conducting empirical researchresearch Deductive reasoning approachDeductive reasoning approach: “Top : “Top

down,” theory-driven methoddown,” theory-driven method Inductive reasoning approachInductive reasoning approach: :

“Bottom up,” data-driven method“Bottom up,” data-driven method Both equally valid modes of conducting Both equally valid modes of conducting

research in any area of scienceresearch in any area of science


Human NatureHuman Nature

Human nature is a product of Human nature is a product of evolutionary processevolutionary process

Psychological mechanisms that are Psychological mechanisms that are successful in helping humans survive successful in helping humans survive and reproduce out-replicate those and reproduce out-replicate those that are less successfulthat are less successful


Human NatureHuman Nature

Over evolutionary time, successful Over evolutionary time, successful mechanisms spread through mechanisms spread through population and come to characterize population and come to characterize all humansall humans

Examples of evolutionary analysis at Examples of evolutionary analysis at the level of human naturethe level of human nature The Need to BelongThe Need to Belong Helping and AltruismHelping and Altruism Universal EmotionsUniversal Emotions


Sex DifferencesSex Differences

Evolutionary psychologists expect Evolutionary psychologists expect that males and females will be the that males and females will be the same or similar in all domains where same or similar in all domains where sexes have faced the same or similar sexes have faced the same or similar adaptive problemsadaptive problems

Expect sex differences in those Expect sex differences in those domains where sexes recurrently domains where sexes recurrently faced different adaptive problemsfaced different adaptive problems


Sex DifferencesSex Differences

Examples of differences between men and Examples of differences between men and women that are attributable to women that are attributable to recurrently facing different adaptive recurrently facing different adaptive problemsproblems Sex Differences in AggressionSex Differences in Aggression Sex Differences in JealousySex Differences in Jealousy Sex Differences in Desire for Sexual Sex Differences in Desire for Sexual

VarietyVariety Sex Differences in Mate PreferencesSex Differences in Mate Preferences


Individual DifferencesIndividual Differences

Most challenging and difficult level of Most challenging and difficult level of analysis for evolutionary psychologistsanalysis for evolutionary psychologists

Three evolutionary perspectives on Three evolutionary perspectives on individual differencesindividual differences Environmental triggers of individual Environmental triggers of individual

differencesdifferences Adaptive self-assessment of heritable Adaptive self-assessment of heritable

individual differences individual differences Frequency-dependent strategic individual Frequency-dependent strategic individual

differences differences


The Big Five and The Big Five and Evolutionarily-Relevant Evolutionarily-Relevant

Adaptive ProblemsAdaptive Problems

Big Five personality traits as Big Five personality traits as clusters of key features of “adaptive clusters of key features of “adaptive landscape” of other peoplelandscape” of other people

Human have evolved “difference-Human have evolved “difference-detecting mechanisms” designed to detecting mechanisms” designed to notice and remember individual notice and remember individual differences that have most relevance differences that have most relevance for solving social adaptive problemsfor solving social adaptive problems


Limitations of Evolutionary Limitations of Evolutionary PsychologyPsychology

Adaptations are forged over long expanse Adaptations are forged over long expanse of evolutionary time, and we cannot go of evolutionary time, and we cannot go back to determine with certainty what the back to determine with certainty what the precise selective forces on humans have precise selective forces on humans have beenbeen Forced to make inferencesForced to make inferences But current mechanisms provide windows But current mechanisms provide windows

for viewing the pastfor viewing the past Learning more about our evolved Learning more about our evolved

mechanisms is a tool for overcoming mechanisms is a tool for overcoming limitation of sparse knowledge of ancestral limitation of sparse knowledge of ancestral environmentsenvironments



Evolutionary scientists have just Evolutionary scientists have just scratched the surface of understanding scratched the surface of understanding the nature, details, and design features the nature, details, and design features of evolved psychological mechanismsof evolved psychological mechanisms

Modern conditions are undoubtedly Modern conditions are undoubtedly different from ancestral conditions in different from ancestral conditions in many ways, and so what was adaptive many ways, and so what was adaptive in the past might not be adaptive todayin the past might not be adaptive today



It is sometimes easy to come up with It is sometimes easy to come up with different and competing evolutionary different and competing evolutionary hypotheses for the same phenomena—true hypotheses for the same phenomena—true of all scienceof all science Onus is on the researcher to fashion Onus is on the researcher to fashion

specific, testable, and falsifiable hypothesesspecific, testable, and falsifiable hypotheses Thus, competing theories can be pitted Thus, competing theories can be pitted

against each other and data can be the final against each other and data can be the final arbiterarbiter



Evolutionary hypotheses are Evolutionary hypotheses are sometimes accused of being sometimes accused of being untestable and hence unfalsifiable, untestable and hence unfalsifiable, but this is no more true than for any but this is no more true than for any other scienceother science


Summary and EvaluationSummary and Evaluation

Selection is key to evolution, or Selection is key to evolution, or change in a species over timechange in a species over time

Variants that lead to greater genetic Variants that lead to greater genetic replication spread through the replication spread through the populationpopulation

Evolutionary psychology has three Evolutionary psychology has three premises: Adaptations are domain-premises: Adaptations are domain-specific, numerous, and functionalspecific, numerous, and functional


Summary and EvaluationSummary and Evaluation(continued)(continued)

Evolutionary psychology proceeds Evolutionary psychology proceeds through both deductive research through both deductive research approach and inductive research approach and inductive research approachapproach

Evolutionary psychology can be Evolutionary psychology can be applied to all three levels of applied to all three levels of personality analysis—human nature, personality analysis—human nature, sex differences, individual differencessex differences, individual differences


Summary and EvaluationSummary and Evaluation(continued)(continued)

Evolutionary psychology has several Evolutionary psychology has several limitations, but this perspective adds limitations, but this perspective adds a useful set of theoretical tools to a useful set of theoretical tools to the analysis of personality at levels the analysis of personality at levels of human nature, sex differences, of human nature, sex differences, and individual differencesand individual differences

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