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Evolutionary Psychology


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A lecture on Evolutionary Psychology, with specific examples from language research.

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Evolutionary Psychology

  1. 2. What is the ecology of the human mind?
  2. 3. The Standard Social Science Model (SSSM) and Evolutionary Psychology (EP) <ul><li>SSSM is the prevailing orthodoxy in anthropology, sociology, and has dominated psychology since the 1940's. </li></ul><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>
  3. 4. Evolutionary Psychology To a first approximation: our modern skulls house a stone age mind.
  4. 5. 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. All science is a single coherent entity consisting of many disciplines e.g. physics, biology, psychology, sociology etc. - all characterized by adoption of the scientific method. There are several types of scientific Endeavour e.g. natural sciences (biology, botany, zoology etc.); social sciences (sociology, psychology, politics etc.) Body structure (e.g. hands, kidneys, eyes) has evolved Body structure (e.g. hands, kidneys, eyes) has evolved According to EP: According to the SSSM:
  5. 6. The human mind consists of specialized modules that are innate and have evolved via natural and sexual selection to cope with adaptive problems. Modules resemble debugged computer programs designed for a particular process e.g. word processor, spreadsheet, database. Fodor (1998) writes that e volutionary psychologists view &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 (its selfish gene, as one says).&quot; Humans are born with a few reflexes and the ability to learn. Essentially we are 'empty computers' or 'blank slates' at birth, written on by the hand of culture and experience. Fodor (1998) expresses this idea as follows: &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. The structure of the mind is thus an image, made a posteriori, of the statistical regularities in the world in which it finds itself. I would guess that quite a substantial majority of cognitive scientists believe something of this sort; so deeply, indeed, that many hardly notice that they do.&quot;  
  6. 7. Many of the reasons for our behavior are unconscious We can arrive at a conscious decision about the best solution to many everyday problems. Culture is a product of specialized modules. For example a page of text is the product of a word processing program. Culture determines what is learnt. Modules are inherited from ancestors who adapted to the EEA. The individual's internal and external environment plays a role in the expression of modules. Rather like setting the preferences for a computer program. Human behavior is acquired during the lifetime of the individual. Modules are specialized to solve particular adaptive problems: For example, mate selection, language, social co-operation. Human behavior is controlled by a general purpose systems which rely on imitation, general intelligence, culture, reward and punishment. These systems are content-independent or domain-general.
  7. 8. 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. 9. 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>
  9. 11. 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>
  10. 12. 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>
  11. 13. Evolved Psychological Mechanisms (Modules) <ul><li>An evolved psychological mechanism EPM (like language) exists in the form that is does because it solved a specific adaptive problem. </li></ul><ul><li>EPM’s respond to a narrow range of stimuli. </li></ul><ul><ul><li>Speech or sign </li></ul></ul>
  12. 14. EPM’s <ul><li>Output can be either physiological activity, cognitive processing or behavior. </li></ul><ul><li>Output 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>
  13. 15. EPM’s lead to behavioral flexibility <ul><li>EPM’s are not rigid instincts, they depend upon modulation by the environment. </li></ul><ul><ul><li>E.g., Language. </li></ul></ul>
  14. 16. 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>
  15. 17. 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>
  16. 18. 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>
  17. 19. 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>
  18. 20. 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>
  19. 21. 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>
  20. 22. 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>
  21. 23. 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>
  22. 24. 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>
  23. 25. 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>
  24. 26. 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>
  25. 27. 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>
  26. 28. Chomsky said: You learn a specific language from data, but there is a lot about Language that you know when you’re born.
  27. 29. Learning language: some observations DP PP N’ N NP visit DP his DP D’ D DP [poss] to the hospital i VP IP V V’ I’ I [past] DP upset j t j <ul><li>Language is complicated. </li></ul>t i her DP
  28. 30. Learning language: some observations <ul><li>Language is complicated </li></ul><ul><li>Children always succeed </li></ul><ul><li>Children arrive at the same language as the rest of their speech community </li></ul><ul><li>This is remarkable, given the data that children learn language from. </li></ul>
  29. 31. The poverty of the stimulus <ul><li>Children learn language from data </li></ul><ul><li>But, this data is deficient in various ways </li></ul>
  30. 32. 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>
  31. 33. The poverty of the stimulus problem <ul><li>The problem: Children reliably acquire a complex system from a degenerate set of data </li></ul><ul><li>The solution: Universal Grammar </li></ul><ul><li>Children are born with a language instinct </li></ul>
  32. 34. Universal Grammar: the basic idea Input (data) Output (grammar) “ An engineer faced with the problem of designing a device for meeting the given input-output conditions would naturally conclude that the basic properties of the output are a consequence of the design of the device. Nor is there any plausible alternative to this assumption” Chomsky (1967) Acquisition device
  33. 35. Universal Grammar <ul><li>Innate linguistic knowledge which guides children during language acquisition. </li></ul><ul><li>defines the range of possible human languages </li></ul><ul><li>gives an acquisition procedure for picking the correct grammar (LAD) </li></ul>
  34. 36. UG and language acquisition <ul><li>UG interacts with the environment: </li></ul><ul><li>Language acquisition is “ the growth of cognitive structures along an internally directed course under the triggering … effect of the environment ” (Chomsky 1980) </li></ul>
  35. 37. Principles and Parameters <ul><li>One way of thinking about UG. </li></ul><ul><li>UG provides: </li></ul>Principles : invariant features of human language. Parameters : a small range of choices that characterize language variation.
  36. 38. A Principle: structure-dependency <ul><li>Syntactic operations depend on constituent structure. </li></ul><ul><li>Example: yes/no questions </li></ul><ul><li>Is i the girl t i tall? </li></ul><ul><li>Is i the dog that is in the garden t i barking? </li></ul><ul><li>Formed by moving main clause auxiliary verb to front of subject DP </li></ul><ul><li>Not, e.g., moving the first aux to the front </li></ul>
  37. 39. Structure-dependency and stimulus poverty <ul><li>The crucial type of example: </li></ul><ul><li>Is i the dog that is in the garden t i barking? </li></ul><ul><li>“ You can go over a vast amount of data of experience without ever finding such a case ” Chomsky, in Piattelli-Palmarini (1980) </li></ul>
  38. 40. Another Principle: recursion <ul><li>All languages are recursive. </li></ul><ul><li>it’s in UG </li></ul><ul><li>kids know it in advance </li></ul>
  39. 41. Principles: a summary <ul><li>UG contains information on invariant properties of language </li></ul><ul><ul><li>Principles </li></ul></ul><ul><li>All languages have these properties </li></ul><ul><ul><li>universal </li></ul></ul><ul><li>Children don’t have to learn these properties </li></ul><ul><ul><li>innate knowledge </li></ul></ul>
  40. 42. Parameter: head-complement ordering <ul><li>What order do heads and complements appear in? </li></ul>IP CP C’ C if VP IP I’ I will DP VP V’ V write DP PP P’ P to
  41. 43. Parameter: head-complement ordering <ul><li>What order do heads and complements appear in? </li></ul>IP CP C’ C ka VP IP I’ I -u DP VP V’ V kak DP PP P’ P ni
  42. 44. Parameter: head-complement ordering <ul><li>The head-order parameter has two settings: </li></ul><ul><li>head-initial </li></ul><ul><li>head-final </li></ul>
  43. 45. Typological data <ul><li>From Dryer (1992) </li></ul>61% Object-Verb, Postposition 3% Object-Verb, Preposition 3% Verb-Object, Postposition 33% Verb-Object, Preposition Percentage of Genera Class
  44. 46. The null subject parameter <ul><li>Yes: tensed clauses can have null subjects </li></ul><ul><li>No: every tensed clause must have an overt subject </li></ul><ul><li>No setting: English (French, Edo, …) </li></ul><ul><li>he speaks </li></ul><ul><li>* speaks </li></ul><ul><li>Yes setting: Italian (Spanish, Navajo, …) </li></ul><ul><li>lui parla </li></ul><ul><li>parla </li></ul>
  45. 47. The null subject parameter <ul><li>Dummy subjects </li></ul><ul><li>it is raining / * is raining </li></ul><ul><li>piove </li></ul><ul><li>Non-movement of subjects </li></ul><ul><li>Alex will come / * will come Alex </li></ul><ul><li>Alex verrá / verrá Alex </li></ul>
  46. 48. A parameter space polysynthesis head directionality subject side verb attraction subject placement serial verb null subject yes no Mohawk, Warlpiri final initial Japanese, Turkish initial final Malagasy, Tzotzil yes no no yes English Edo, Khmer high low Welsh, Zapotec no yes French Spanish, Romanian
  47. 49. Principles and Parameters: summary <ul><li>Principles : provided by UG, invariant </li></ul><ul><li>Parameters : provided by UG, languages vary in parameter settings </li></ul><ul><li>P&P explains: </li></ul><ul><li>language acquisition </li></ul><ul><li>language universals </li></ul><ul><li>linguistic variation </li></ul>
  48. 50. Universal Grammar: summary <ul><li>The poverty of the stimulus problem </li></ul><ul><ul><li>language can’t be learned purely from the data children are exposed to. </li></ul></ul><ul><li>Children must have innate linguistic knowledge </li></ul><ul><ul><li>Universal Grammar </li></ul></ul><ul><li>Principles and Parameters approach </li></ul><ul><ul><li>one way of thinking about UG </li></ul></ul>
  49. 51. Stimulus Expectant vs. Stimulus Dependent <ul><li>Expectant </li></ul><ul><ul><li>Attachment </li></ul></ul><ul><ul><li>Walking </li></ul></ul><ul><ul><li>Language (1st) </li></ul></ul><ul><ul><li>Love </li></ul></ul><ul><ul><li>Sex </li></ul></ul><ul><li>Dependent </li></ul><ul><ul><li>Driving </li></ul></ul><ul><ul><li>Reading </li></ul></ul><ul><ul><li>Chess </li></ul></ul><ul><ul><li>Yahtzee </li></ul></ul><ul><ul><li>Algebra </li></ul></ul><ul><ul><li>Language (2nd; with some influence of 1st) </li></ul></ul>
  50. 52. Places to learn more: <ul><li>Cosmides & Tooby, Evolutionary Psychology: A Primer. </li></ul><ul><li>Pinker, S. The Blank Slate. </li></ul><ul><li>Pinker, S. How The Mind Works. </li></ul><ul><li>Hauser, M. Moral Minds. </li></ul>