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An Evolutionary approach to personality
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Chapter Outline

Evolutionary Perspectives on Personality

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
  • We carry adaptive mechanisms that led to our ancestors' success
  • Human nature and human personality made up of a collection of evolved mechanisms
  • Before Darwin, two features of evolution were recognized: Change over time and apparent adaptation to environment
  • Natural Selection
    • Darwin revolutionized biology by proposing a theory of the process by which adaptations are created and changes take place over time—natural selection
    • More offspring produced than can survive and reproduce
    • 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
    • Thus, successful variants are selected and unsuccessful variants are weeded out
    • Over time, successful variants come to characterize entire species
    • Adaptations; inherited solutions to survival and reproductive problems posed by hostile forces of nature
    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 proposed evolution by sexual selection as solution—these traits evolved because they contributed to an individual's mating success
    • 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
      • Intersexual competition: Members of one sex choose a mate based on their preferences for particular qualities in that mate
    Genes and Inclusive Fitness
    • Gene—packet of DNA inherited by children from parents; smallest discrete unit inherited without being broken up
    • Discovery of the gene as a unit of inheritance led to key discovery, that natural selection and sexual selection are different forms of the same process
    • Differential gene reproduction—reproductive success relative to others
    • 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
    Products of the Evolutionary Process
      • 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"
      • Adaptive problem: Anything that impedes survival or reproduction
      • Hallmark of adaptations are special design, including efficiency, precision, and reliability
      Byproducts of Adaptations
      • Byproducts are incidental effects of adaptations not properly considered to be adaptations
      Noise or Random Variation
      • Neutral with respect to selection
Evolutionary Psychology and Human Nature
    Premises of Evolutionary Psychology
    • Domain-specificity: Adaptations are designed by evolutionary process to solve specialized adaptive problems
    • Numerousness: Expectation is that there are many psychological adaptations, because different adaptations are required to solve different adaptive problems
    • Functionality: Psychological adaptations are designed to accomplish particular adaptive goals
    Empirical Testing of Evolutionary Hypotheses
    • Hierarchy of levels of analysis in evolutionary psychology
      • General evolutionary theory
      • Middle-level evolutionary theories
      • Specific hypotheses
      • Specific, testable, falsifiable predictions
    • Two modes of conducting empirical research
      • Deductive reasoning approach: "Top down," theory-driven method
      • Inductive reasoning approach: "Bottom up," data-driven method
      • Both equally valid modes of conducting research in any area of science, including evolutionary psychology
Human Nature
  • 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
  • Over evolutionary time, successful mechanisms spread through population and come to characterize all humans
  • Examples of evolutionary analysis at the level of human nature
    • The Need to Belong
    • Helping and Altruism
    • Universal Emotions
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
  • Expect sex differences in those domains where sexes recurrently faced 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 Jealousy
    • Sex Differences in Desire for Sexual Variety
    • Sex Differences in Mate Preferences
Individual Differences
  • Most challenging and difficult level of analysis for evolutionary psychologists
  • Most challenging and difficult level of analysis for evolutionary psychologists
    • Environmental effects on species-typical patterns—e.g., father absence directing individuals toward short-term sexual strategy
    • Adaptive self-assessment of heritable qualities—e.g., individuals who are muscular and large pursue a more aggressive strategy than those who are less muscular and smaller
    • Frequency-dependent alternative strategies—e.g., short-term and long-term sexual strategies of women are maintained in the population at a frequency where reproductive benefits of strategies are equal
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
    • Forced to make inferences
    • 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
  • 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
  • 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
    • Thus, competing theories can be pitted against each other and data can be the final arbiter
  • Evolutionary hypotheses are sometimes accused of being untestable and hence unfalsifiable, but this is no more true than for any other science
Summary and Evaluation
  • Selection is key to evolution, or change in a species over time
  • Variants that lead to greater genetic replication spread through the population
  • Evolutionary psychology has three premises: Adaptations are domain-specific, numerous, and functional
  • Evolutionary psychology proceeds through both deductive research approach and inductive research approach
  • Evolutionary psychology can be applied to all three levels of personality analysis—human nature, sex differences, 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