Evolutionary Perspectives on Personality

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin Theories Three theories of the origins of complex adaptive mechanisms Three theories of the origins of complex adaptive mechanisms

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Creationism

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2. Seeding theory

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3. Evolution by natural selection

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Evolution and Natural Selection All humans today come from an unbroken line of ancestors who accomplished two tasks: They survived to reproductive age, and they reproduced All humans today come from an unbroken line of ancestors who accomplished two tasks: They survived to reproductive age, and they reproduced We carry adaptive mechanisms that led to our ancestors’ success We carry adaptive mechanisms that led to our ancestors’ success

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Natural Selection Changes or variants that better enabled an organism to survive and reproduce lead to more descendants Changes or variants that better enabled an organism to survive and reproduce lead to more descendants Descendants inherit variants that led to their ancestors’ success Descendants inherit variants that led to their ancestors’ success

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Natural Selection Thus, successful variants are selected and unsuccessful variants are weeded out Thus, successful variants are selected and unsuccessful variants are weeded out Over time, successful variants come to characterize entire species Over time, successful variants come to characterize entire species

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sexual Selection Darwin noticed that many mechanisms seemed to threaten survival, such as the peacock’s elaborate plumage and the stag’s large antlers Darwin noticed that many mechanisms seemed to threaten survival, such as the peacock’s elaborate plumage and the stag’s large antlers Darwin proposed evolution by sexual selection as solution—these traits evolved because they contributed to an individual’s mating success Darwin proposed evolution by sexual selection as solution—these traits evolved because they contributed to an individual’s mating success

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

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sexual Selection Two forms of sexual selection Two forms of sexual selection Intrasexual competition: Members of the same sex compete with each other for sexual access to members of the other sex Intrasexual competition: Members of the same sex compete with each other for sexual access to members of the other sex Intersexual competition: Members of one sex choose a mate based on their preferences for particular qualities in that mate Intersexual competition: Members of one sex choose a mate based on their preferences for particular qualities in that mate

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Genes and Inclusive Fitness Differential gene reproduction—reproductive success relative to others Differential gene reproduction—reproductive success relative to others Calculate genetic gains and losses Calculate genetic gains and losses Inclusive fitness theory (Hamilton, 1964) Inclusive fitness theory (Hamilton, 1964) Inclusive fitness: personal reproductive success (number of offspring you produce) plus effects you have on the reproduction of your genetic relatives, weighted by genetic relatedness Inclusive fitness: personal reproductive success (number of offspring you produce) plus effects you have on the reproduction of your genetic relatives, weighted by genetic relatedness

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Products of the Evolutionary Process Adaptations Adaptations Byproducts of Adaptations Byproducts of Adaptations Noise or Random Variation Noise or Random Variation

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Adaptations Adaptations are the primary products of selection, defined as “reliably developing structure in the organism which, because it meshes with the recurrent structure of the world, causes the solution to an adaptive problem” Adaptations are the primary products of selection, defined as “reliably developing structure in the organism which, because it meshes with the recurrent structure of the world, causes the solution to an adaptive problem”

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Adaptations Adaptive problem: Anything that impedes survival or reproduction Adaptive problem: Anything that impedes survival or reproduction Hallmark of adaptations are special design, including efficiency, precision, and reliability. Hallmark of adaptations are special design, including efficiency, precision, and reliability. E.g., food preferences, fear of snakes E.g., food preferences, fear of snakes E.g. Jealousy, helping, defense mechanisms E.g. Jealousy, helping, defense mechanisms

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Byproducts of Adaptations Byproducts are incidental effects of adaptations not properly considered to be adaptations Byproducts are incidental effects of adaptations not properly considered to be adaptations e.g., nose e.g., nose e.g., language? e.g., language?

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Noise or Random Variation Neutral with respect to selection Neutral with respect to selection e.g., shape of the human earlobe e.g., shape of the human earlobe

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Evolutionary Psychology Premises of Evolutionary Psychology Premises of Evolutionary Psychology Domain-specificity: Adaptations are designed by evolutionary process to solve specialized adaptive problems Domain-specificity: Adaptations are designed by evolutionary process to solve specialized adaptive problems

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Evolutionary Psychology Premises of Evolutionary Psychology Premises of Evolutionary Psychology Numerousness: Expectation is that there are many psychological adaptations, because different adaptations are required to solve different adaptive problems Numerousness: Expectation is that there are many psychological adaptations, because different adaptations are required to solve different adaptive problems

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Evolutionary Psychology Premises of Evolutionary Psychology Premises of Evolutionary Psychology Functionality: Psychological adaptations are designed to accomplish particular adaptive goals Functionality: Psychological adaptations are designed to accomplish particular adaptive goals

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Proximate and Ultimate Causation Proximate causation: Immediate causal forces— development, input, mechanism Proximate causation: Immediate causal forces— development, input, mechanism E.g., defense mechanisms used to avoid anxiety E.g., defense mechanisms used to avoid anxiety Ultimate causation: Why? [example: Why are men taller than women, on average?] Ultimate causation: Why? [example: Why are men taller than women, on average?] E.g., why do defense mechanisms exist? E.g., why do defense mechanisms exist?

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Core Tenets of Evolutionary Psychology Evolved psychological mechanisms are instantiated in the brain. Evolved psychological mechanisms are instantiated in the brain.

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Nature Human nature is a product of evolutionary process Human nature is a product of evolutionary process Psychological mechanisms that are successful in helping humans survive and reproduce out- replicate those that are less successful Psychological mechanisms that are successful in helping humans survive and reproduce out- replicate those that are less successful

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Nature Over evolutionary time, successful mechanisms spread through population and come to characterize all humans Over evolutionary time, successful mechanisms spread through population and come to characterize all humans Examples of evolutionary analysis at the level of human nature Examples of evolutionary analysis at the level of human nature The Need to Belong The Need to Belong Helping and Altruism Helping and Altruism Defense Mechanisms Defense Mechanisms Universal Emotions Universal Emotions

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Nature The Need To Belong  The most basic human motivators are status and acceptance  Social Anxiety – species typical adaptation to prevent social exclusion  Being part of a group has survival value

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Nature Helping and Altruism  Helping others is a direct function of the recipient’s ability to enhance the inclusive fitness of the helper  The tendency to help is a direct function of genetic relatedness

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Nature Helping and Altruism  Who do you save from a burning building?  Son vs. nephew?  Son vs. daughter?  Spouse vs. child?

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Nature Defense Mechanisms  Ability to deceive self (DM) increases ability to deceive others  Deceiving others increases likelihood of survival and mating success  E.g., threats, boss

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sex Differences Evolutionary psychologists expect that males and females will be the same or similar in all domains where sexes have faced the same or similar adaptive problems Evolutionary psychologists expect that males and females will be the same or similar in all domains where sexes have faced the same or similar adaptive problems Expect sex differences in those domains where sexes recurrently faced different adaptive problems Expect sex differences in those domains where sexes recurrently faced different adaptive problems

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sex Differences Examples of differences between men and women that are attributable to recurrently facing different adaptive problems Examples of differences between men and women that are attributable to recurrently facing different adaptive problems Sex Differences in Aggression Sex Differences in Aggression Sex Differences in Jealousy Sex Differences in Jealousy Sex Differences in Desire for Sexual Variety Sex Differences in Desire for Sexual Variety Sex Differences in Mate Preferences Sex Differences in Mate Preferences

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sex Differences Jealousy  Adaptive problem for men is paternity.  Men over evolutionary history have risked investing in children who were not their own  Adaptive problem for women is child-rearing resources.  Women over evolutionary history have risked raising children without adequate resources

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sex Differences Jealousy  Males and females have evolved different jealousy cues  Men should be more jealous in response to cues to a sexual infidelity  Women become more distressed over a partner’s emotional infidelity

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sex Differences Basic Method Think of a serious, committed romantic relationship that you have had in the past, that you currently have, or that you would like to have. Imagine that you discover that the person with whom you’ve been seriously involved has become more interested in someone else. Of the following, which would distress or upset you more? 1. Imagining your partner forming a deep emotional attachment to that person. 2. Imagining your partner enjoying passionate sexual intercourse with that person.

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sex Differences Jealousy Findings Universal Problems Forced choice only Double shot

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sex Differences Mate Preferences  Evolutionary psychology predicts:  Men value women’s physical appearance which provides cues to her fertility  Women value men’s financial resources which help in raising the family

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Individual Differences Most challenging and difficult level of analysis for evolutionary psychologists Most challenging and difficult level of analysis for evolutionary psychologists Big Five personality traits as clusters of key features of “adaptive landscape” of other people Big Five personality traits as clusters of key features of “adaptive landscape” of other people Human have evolved “difference-detecting mechanisms” designed to notice and remember individual differences that have most relevance for solving social adaptive problems Human have evolved “difference-detecting mechanisms” designed to notice and remember individual differences that have most relevance for solving social adaptive problems

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Limitations of Evolutionary Psychology Adaptations are forged over long expanse of evolutionary time, and we cannot go back to determine with certainty what the precise selective forces on humans have been Adaptations are forged over long expanse of evolutionary time, and we cannot go back to determine with certainty what the precise selective forces on humans have been Forced to make inferences Forced to make inferences But current mechanisms provide windows for viewing the past But current mechanisms provide windows for viewing the past Learning more about our evolved mechanisms is a tool for overcoming limitation of sparse knowledge of ancestral environments Learning more about our evolved mechanisms is a tool for overcoming limitation of sparse knowledge of ancestral environments

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Limitations of Evolutionary Psychology Evolutionary scientists have just scratched the surface of understanding the nature, details, and design features of evolved psychological mechanisms Evolutionary scientists have just scratched the surface of understanding the nature, details, and design features of evolved psychological mechanisms Modern conditions are undoubtedly different from ancestral conditions in many ways, and so what was adaptive in the past might not be adaptive today Modern conditions are undoubtedly different from ancestral conditions in many ways, and so what was adaptive in the past might not be adaptive today

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Limitations of Evolutionary Psychology It is sometimes easy to come up with different and competing evolutionary hypotheses for the same phenomena—true of all science It is sometimes easy to come up with different and competing evolutionary hypotheses for the same phenomena—true of all science Onus is on the researcher to fashion specific, testable, and falsifiable hypotheses Onus is on the researcher to fashion specific, testable, and falsifiable hypotheses Thus, competing theories can be pitted against each other and data can be the final arbiter Thus, competing theories can be pitted against each other and data can be the final arbiter

Copyright © 2005 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Summary and Evaluation (continued) Evolutionary psychology has several limitations, but this perspective adds a useful set of theoretical tools to the analysis of personality at levels of human nature, sex differences, and individual differences Evolutionary psychology has several limitations, but this perspective adds a useful set of theoretical tools to the analysis of personality at levels of human nature, sex differences, and individual differences