Evolutionary Psychology

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Evolutionary Psychology

  1. 1. What is the ecology of the human mind?
  2. 2. The Standard Social Science Model (SSSM) <ul><li>SSSM is the prevailing orthodoxy in anthropology, sociology, and has dominated psychology since the 1940's. </li></ul>
  3. 3. The Blank Slate <ul><li>Fodor (1998) expresses this idea as follows: </li></ul><ul><li>&quot;Most cognitive scientists still work in a tradition of empiricism and associationism whose main tenets haven't changed much since Locke and Hume. The human mind is a blank slate at birth . Experience writes on the slate, and association extracts and extrapolates whatever trends there are in the record that experience leaves.&quot; </li></ul>
  4. 4. Evolutionary Psychology <ul><li>The SSSM is under challenge from Evolutionary Psychology (EP) which has mounted a critique of contemporary psychology because it has largely ignored the role of evolution in shaping human behavior . </li></ul>
  5. 5. Evolutionary Psychology <ul><li>Fodor (1998) writes that e volutionary psychologists view… </li></ul><ul><li>&quot;..the mind as computational system; the mind is massively modular; a lot of mental structure, including a lot of cognitive structure, is innate; a lot of mental structure, including a lot of cognitive structure, is an evolutionary adaptation - in particular, the function of a creature's nervous system is to abet the propagation of its genome …&quot; </li></ul>
  6. 6. Animal and human behavior are biological phenomena that have evolved. Ignorance of evolutionary theory can lead some psychologists to appear to view humans as having progressed to be above apes and other 'lower' animals on a 'scale of nature' or scala naturae . Animal behavior is controlled by their biology. Human behavior is determined by culture and experience. Animal behavior is more appropriately studied by biologists. Biology is a natural science. Biology is built upon the rock of evolutionary theory. Psychology is a branch of biology. Psychology is a social science. Social sciences are concerned with how culture and experience produce wide variation in human behavior. Therefore social sciences do not need to consider the role of evolution in the development of behavioral variability. According to EP: According to the SSSM:
  7. 7. Evolutionary Psychology <ul><li>Evolutionary psychologists propose that humans evolved tendencies to think, feel, and behave in certain ways, and not others... </li></ul>
  8. 8. Darwin’s Theory <ul><li>Three major principles : </li></ul><ul><ul><li>1. heredity </li></ul></ul><ul><ul><ul><li>characteristics are passed from one generation to the next </li></ul></ul></ul><ul><ul><li>2. variability </li></ul></ul><ul><ul><ul><li>characteristics vary across members of a species </li></ul></ul></ul><ul><ul><ul><li>some individuals will be more successful in their environment than others </li></ul></ul></ul><ul><ul><ul><li>demand for resources produces selective pressure </li></ul></ul></ul>
  9. 9. Darwin’s Theory <ul><li>Three major principles : </li></ul><ul><ul><li>3. natural selection (“survival of the fittest”) </li></ul></ul><ul><ul><ul><li>how species change, or evolve, over time </li></ul></ul></ul><ul><ul><ul><li>only those members of a species able to compete successfully for limited resources will survive and reproduce </li></ul></ul></ul>
  10. 10. Interpreting Darwin <ul><li>Two common errors: </li></ul><ul><ul><li>1. assuming that evolution means “progress” </li></ul></ul><ul><ul><ul><li>Or, as species evolve, they improve </li></ul></ul></ul><ul><ul><ul><li>evolution simply means change and adaptation to an environment </li></ul></ul></ul><ul><ul><ul><li>not “better,” but “better adapted” </li></ul></ul></ul>
  11. 11. Interpreting Darwin <ul><li>Two common errors: </li></ul><ul><ul><li>2. “survival of the strongest” </li></ul></ul><ul><ul><ul><li>fit simply means best able to survive and reproduce in the environment </li></ul></ul></ul>
  12. 12. Mechanisms of Evolution <ul><li>For natural selection to produce evolutionary adaptations, there needs to be a mechanism for producing variation within a species. </li></ul><ul><li>And there needs to be some mechanism by which an adaptive trait can pass from one generation to the next. </li></ul>
  13. 13. Mechanisms of Evolution <ul><li>Genes - the biological units of heredity </li></ul><ul><ul><li>Genotype: genetic information inherited from one’s parents </li></ul></ul><ul><ul><li>Phenotype: a person’s observable characteristics </li></ul></ul>
  14. 14. The Three Products of Evolution <ul><li>Adaptations : Inherited and reliably developing characteristics that came into existence through natural selection because they aided in solving problems related to survival and/or reproduction. </li></ul><ul><ul><ul><li>Example: umbilical cord </li></ul></ul></ul><ul><li>By-products : Characteristics that do not solve adaptive problems and do not have functional design. They are coupled to adaptations. </li></ul><ul><ul><ul><li>Example: belly button </li></ul></ul></ul><ul><li>Noise :Random effects produced by genetic drift and chance mutations that do not affect survival and/or reproductive success. </li></ul>
  15. 15. Human Evolution <ul><li>Many aspects of human behavior that probably reflect evolutionary adaptations do not increase survival and reproduction in contemporary environments. </li></ul>Hence, Snakes on a Plane.
  16. 16. Human Evolution <ul><li>infant reflexes </li></ul><ul><ul><ul><li>Some are evolutionary carry-overs </li></ul></ul></ul><ul><ul><ul><li>Swimming reflex </li></ul></ul></ul><ul><ul><ul><li>Moro reflex – unnecessary </li></ul></ul></ul><ul><li>fats and sugars - evolved tastes </li></ul><ul><ul><li>Backfires in contemporary environments </li></ul></ul>
  17. 17. Mismatch Theory <ul><li>Have to consider the environments in which a species’ evolutionary adaptations were selected; in which our ancestors lived for millions of years prior to the rise of agriculture. </li></ul>
  18. 18. Mismatch Theory <ul><li>Compare this with modern environments to explain maladaptive behaviour today. </li></ul><ul><li>Modern human brain consists of modules from the past. </li></ul>
  19. 19. Evolutionary Psychology To a first approximation: our modern skulls house a stone age mind.
  20. 20. Basics of Evolutionary Psychology <ul><li>Evolutionary Psychologists argue that natural selection designed our minds to deal with problems that we faced on the African savannahs. </li></ul><ul><ul><li>The savannah was our Environment of Evolutionary Adaptedness (EEA). </li></ul></ul>
  21. 22. Environment of Evolutionary Adaptedness (EEA) <ul><li>Therefore our mind consists of a collection of adaptations . Each individual adaptation has evolved to meet challenges faced in our EEA. </li></ul><ul><li>An adaptation is &quot;a characteristic that has arisen through and been shaped by natural and or sexual selection. It regularly develops in members of the same species because it helped to solve problems of survival and reproduction in the evolutionary ancestry of the organism. Consequently it can be expected to have a genetic basis ensuring that the adaptation is passed through the generations. &quot; (Williams, 1966) </li></ul>
  22. 23. In Every Known Human Culture: <ul><li>tool making </li></ul><ul><li>weapons </li></ul><ul><li>grammar </li></ul><ul><li>tickling </li></ul><ul><li>meal times </li></ul><ul><li>mediation of conflicts </li></ul><ul><li>dance, singing </li></ul><ul><li>personal names </li></ul><ul><li>promises </li></ul><ul><li>mourning </li></ul>(Donald E. Brown, 1991. Human universals. New York: McGraw-Hill.)
  23. 24. Evolved Psychological Mechanisms (modules) <ul><li>An evolved psychological mechanism EPM exists in the form that is does because it solved a specific adaptive problem. </li></ul><ul><li>Problem: who’s my mommy? </li></ul><ul><ul><li>Example: Facial recognition -- newborn babies preferentially look at human faces. </li></ul></ul><ul><ul><li>Important for recognizing kin. </li></ul></ul>
  24. 25. EPM’s <ul><li>Am EPM can take the form of either a physiological activity, cognitive processing or behavior. </li></ul><ul><li>The EPM is directed towards solving the adaptive problem. </li></ul><ul><li>Important Point: EPM’s that led to effective solutions in the past may no longer be effective now (vestigial). </li></ul><ul><ul><li>Example: piloerrection (I.e. goose bumps) </li></ul></ul>
  25. 26. Problems Faced by Ancestral Humans <ul><li>Problems of Survival : Getting the organism to a point where it is capable of reproducing. </li></ul><ul><li>Problems of Mating : Selecting, attracting and retaining a mate long enough to reproduce. </li></ul><ul><li>Problems of Parenting : Helping offspring survive long enough that they are capable of reproducing. </li></ul><ul><li>Problems of aiding genetic relatives : Tasks relevant to assisting non-descendent kin. </li></ul>
  26. 27. Example <ul><li>Imagine a population of omnivores that lacked the capability to digest rancid meat. </li></ul><ul><ul><li>The byproducts of bacterial activity in rancid meat are therefore toxic to this species. </li></ul></ul><ul><li>Imagine that this species had no EPM to stimulate avoidance of rancid meat. </li></ul><ul><li>Each individual would have to learn through trial and error what smells, tastes etc… signaled that meat was not fit for consumption. </li></ul><ul><li>Now imagine that certain individuals were born with an aversion to the smell of rancid meat. </li></ul><ul><li>Which individuals would have a higher fitness? </li></ul>
  27. 28. Human Survival Problems <ul><li>Food selection : The most general problem in food selection is how to obtain adequate amounts of calories and essential vitamins. </li></ul><ul><ul><li>However, we must also avoid poisoning ourselves. </li></ul></ul><ul><li>Plants have adapted toxins that help reduce the odds that the plant will be eaten. </li></ul><ul><li>Hypothesis: humans have evolved taste preferences to avoid toxic materials. </li></ul><ul><li>How do we test this? </li></ul>
  28. 29. Taste Aversions <ul><li>Evidence suggests that the materials that smell and taste bad to humans are also the materials that are potentially harmful to us. </li></ul><ul><ul><li>Broccoli and brussel sprouts contain allylisothiocynate which can be toxic in children (Nesse & Williams 1994) </li></ul></ul><ul><li>We have adaptive mechanisms for removing harmful materials from our body. </li></ul><ul><ul><li>Vomiting. </li></ul></ul>
  29. 30. Morning Sickness <ul><li>The percentage of women who experience morning sickness has been reported to be anywhere from 75 – 89%. However, estimates suggest that the actual % is near 100. </li></ul><ul><li>Hypothesis: Morning sickness is an adaptation to avoid consuming teratogens during the critical period in the development of the fetus. </li></ul><ul><ul><li>Evidence: The foods that pregnant women report to be most nauseating are correlated with high levels of toxins. </li></ul></ul><ul><ul><li>Evidence: Morning sickness occurs at the same time that the fetus is most vulnerable to toxins. </li></ul></ul><ul><ul><li>Evidence: Morning sickness decrease around the same time that the period critical for fetal development has passed. </li></ul></ul>
  30. 31. Morning Sickness <ul><li>Remember, an adaptation must confer an increase in fitness. </li></ul><ul><li>Hypothesis: Women who do not experience morning sickness will be more likely to have problems during their pregnancy. </li></ul><ul><ul><li>Evidence: Women who do not experience M.S. are 3 times more likely to experience a spontaneous abortion (Profet, 1992) </li></ul></ul>
  31. 32. Human Fears <ul><li>Fear can be viewed as an adaptive response to avoid situations that may lead to injury or death. </li></ul><ul><li>Have humans evolved adaptive fear responses to specific stimuli? Or do humans learn fear responses through conditioning? </li></ul>
  32. 33. Common Fears and Phobias <ul><li>The majority of reported fears and phobias involve: </li></ul><ul><ul><li>Spatial stimuli: heights, confined spaces </li></ul></ul><ul><ul><li>Specific animals: snakes, bats, spiders </li></ul></ul><ul><ul><li>The dark </li></ul></ul><ul><ul><li>Public speaking </li></ul></ul><ul><li>There have been very few reported phobias of electricity, cars, busses, power tools, wood stoves, lawn mowers, mountain bikes, X-ray machines, cell phones etc… </li></ul>
  33. 34. Prepared Fears <ul><li>Mineka (1983) observed that rhesus monkeys raised in captivity did not show a fear response when confronted with a snake. </li></ul><ul><li>If these monkeys were shown videos of other monkeys displaying fear in the presence of a snake the subject monkeys quickly acquired the same fear response (same for crocodile). </li></ul><ul><li>If captive raised monkeys were shown a video of monkeys displaying fear in the presence of a pot of flowers the subject monkeys did not acquire a fear response to flower pots (same for rabbit). </li></ul>
  34. 35. Prepared Fears in Humans <ul><li>Human subjects more quickly form associations between images of snakes or spiders and a mild electric shock than between images of electrical cords or mushrooms and a mild electric shock. </li></ul><ul><li>They also report that the shocks that occur after images of snakes and spiders are more painful! </li></ul>
  35. 36. Sexual Jealousy <ul><li>The situation of having a mate and having that mate have sex with someone else. </li></ul><ul><li>This situation occurred often over time and constitutes infidelity. </li></ul><ul><li>Evolutionary Problem: threatens the mate’s chance for reproductive success/ sperm competition. </li></ul><ul><li>Cues: observing a sexual act, flirtation and then even associated elements, once you suspect your mate is cheating you think you may have been lied too, that your mate may have had sex with someone else, etc.. </li></ul><ul><li>The emotion that evolved from this: Sexual Jealousy </li></ul><ul><li>Sexual Jealousy- prepares you for things such as violence, sperm competition, withdrawal of investment, murdering the rival emerges. </li></ul><ul><li>Comides, L., & Tooby, J. Evolutionary psychology and the emotions. In M. Lewis, & J.M.Haviland-Jones (Ed.), Handbook of Emotions (pp. 91-114). New York: Guilford. </li></ul>
  36. 37. The Case of Language <ul><li>Language is a perfect example of an Evolved Psychological Module. </li></ul><ul><li>Chomsky: Inborn Universal Grammar (nativist) </li></ul>
  37. 38. The poverty of the stimulus problem <ul><li>A paradox: Children reliably acquire a complex system from a degenerate set of data. </li></ul><ul><ul><li>The language that children hear is incomplete. </li></ul></ul><ul><ul><li>They know things that they are never exposed to. </li></ul></ul>
  38. 39. The poverty of the stimulus <ul><li>children exposed to data containing errors </li></ul><ul><li>different children exposed to different data </li></ul><ul><li>children don’t get negative evidence </li></ul><ul><li>children aren’t directly rewarded </li></ul><ul><li>children get incomplete data </li></ul>
  39. 40. The poverty of the stimulus problem <ul><li>A solution: Universal Grammar </li></ul><ul><li>Children are born with a language instinct </li></ul>
  40. 41. Evolutionary Psychology <ul><li>Evolutionary adaptations are general and flexible </li></ul><ul><ul><li>e.g., have not evolved to understand specific languages, such as French or English </li></ul></ul>
  41. 42. EPM’s can lead to creativity <ul><li>EPM’s are not rigid instincts, but can change and develop in the species according to the environment. </li></ul><ul><ul><li>Example: Language has pidgins and creoles that have developed in environments where there was no existing language. </li></ul></ul>
  42. 43. Mind as Swiss Army Knife <ul><li>The human mind is the Swiss Army Knife that has all the tools. </li></ul><ul><li>Different species have different sets of tools. </li></ul>

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