Evolutionary Psychology

Evolutionary Psychology Modern skulls house a stone age mind

Basics of Evolutionary Psychology • Evolutionary Psychologists argue that natural selection designed our minds to deal with problems that we faced on the African savannahs. • The savannah was our Environment of Evolutionary Adaptedness (EEA).

Environment of Evolutionary Adaptedness (EEA) • Therefore our mind consists of a collection of adaptations. Each individual adaptation has evolved to meet challenges faced in our EEA. • "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." (Williams, 1966)

The three products of evolution • 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. • Example: umbilical cord • By-products: Characteristics that do not solve adaptive problems and do not have functional design. They are coupled to adaptations. • Example: belly button • Noise:Random effects produced by genetic drift and chance mutations that do not affect survival and/or reproductive success.

Behavioral tendencies as adaptations • It can be shown that humans have evolved physiological traits in response to adaptive pressures. • The brain is the basis of all behavior, and the brain is a physiological structure that has evolved over time. • Therefore, the product of the brain, human behavior, has evolved certain characteristics as well to better meet the demands of the environment. • We can see the cumulative effects of selective pressures when we observe human behavior.

Evolved Psychological Mechanisms (Modules) • An evolved psychological mechanism EPM exists in the form that is does because it solved a specific adaptive problem. • EPM’s respond to a narrow range of stimuli. • Input of an EPM orients the organism to the adaptive problem it is facing. • Example: pizza smell vs. snake • Input to an EPM is subject to decision rules before producing output. • Decision rules: if-then statements based upon experience

EPM’s • Output can be either physiological activity, cognitive processing or behavior. • Output is directed towards solving the adaptive problem. • Important Point: EPM’s that led to effective solutions in the past may no longer be effective now (vestigial). • Example: piloerrection (I.e. goose bumps)

EPM’s lead to behavioral flexibility • EPM’s are not rigid instincts, they depend upon modulation by the environment. • E.g., Language. • Decision rules create response options. • EPM’s cut down on learning time and constrain behaviors into a range that inhibits behaviors that are maladaptive.

Example • Imagine a population of omnivores that lacked the capability to digest rancid meat. • The byproducts of bacterial activity in rancid meat are therefore toxic to this species. • Imagine that this species had no EPM to stimulate avoidance of rancid meat. • Each individual would have to learn through trial and error what smells, tastes etc… signaled that meat was not fit for consumption. • Now imagine that certain individuals were born with an aversion to the smell of rancid meat. • Which individuals would have a higher fitness?

The Standard Social Science Model (SSSM) and Evolutionary Psychology (EP) • SSSM is the prevailing orthodoxy in anthropology, sociology, and has dominated psychology since the 1940's. • 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.

Problems Faced by Ancestral Humans • Problems of Survival: Getting the organism to a point where it is capable of reproducing. • Problems of Mating: Selecting, attracting and retaining a mate long enough to reproduce. • Problems of Parenting: Helping offspring survive long enough that they are capable of reproducing. • Problems of aiding genetic relatives: Tasks relevant to assisting non-descendent kin.

Human Survival Problems • Food selection: The most general problem in food selection is how to obtain adequate amounts of calories and essential vitamins. • However, we must also avoid poisoning ourselves. • Plants have adapted toxins that help reduce the odds that the plant will be eaten. • Hypothesis: humans have evolved taste preferences to avoid toxic materials. • How do we test this?

Taste Aversions • Evidence suggests that the materials that smell and taste bad to humans are also the materials that are potentially harmful to us. • Broccoli and brussel sprouts contain allylisothiocynate which can be toxic in children (Nesse & Williams 1994) • We have adaptive mechanisms for removing harmful materials from our body. • Vomiting.

Morning Sickness • 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. • Hypothesis: Morning sickness is an adaptation to avoid consuming teratogens during the critical period in the development of the fetus. • Evidence: The foods that pregnant women report to be most nauseating are correlated with high levels of toxins. • Evidence: Morning sickness occurs at the same time that the fetus is most vulnerable to toxins. • Evidence: Morning sickness decrease around the same time that the period critical for fetal development has passed.

Morning Sickness • Remember, an adaptation must confer an increase in fitness. • Hypothesis: Women who do not experience morning sickness will be more likely to have problems during their pregnancy. • Evidence: Women who do not experience M.S. are 3 times more likely to experience a spontaneous abortion (Profet, 1992)

Expectant Walking Language (1st) Attachment Love Sex Dependent Driving Reading Chess Algebra Language (2nd) Stimulus Expectant vs.Stimulus Dependent

Prepared Learning • In the 60’s John Garcia conducted a series of studies on taste aversion in rats. • Rats could quickly associate a novel taste with sickness even if the sickness did not occur until hours after experiencing the novel taste. • Rats could not associate a novel color or texture with sickness without repeated exposure. • Harlow (1971) experiments with infant monkeys. • Infant monkeys prefer soft terry cloth surrogate mothers to wire mesh mothers even if only the wire mesh mothers feed the infants.

Prepared Learning • There appears to be adaptive predispositions to quickly acquire specific associations. • That is, learning is biologically constrained. • Organisms can quickly form associations between stimuli and responses that are (or were) relevant to their survival in normal situations.

Human Fears • Fear can be viewed as an adaptive response to avoid situations that may lead to injury or death. • Have humans evolved adaptive fear responses to specific stimuli? Or do humans learn fear responses through conditioning?

Common Fears and Phobias • The majority of reported fears and phobias involve: • Spatial stimuli: heights, confined spaces • Specific animals: snakes, bats, spiders • The dark • Public speaking • 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…

Prepared Fears • Mineka (1983) observed that rhesus monkeys raised in captivity did not show a fear response when confronted with a snake. • 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) • 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)

Prepared Fears in Humans • 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. • They also report that the shocks that occur after images of snakes and spiders are more painful!

The Case of Language Skinner: Operant learning (empiricist) Vs. Chomsky: Inborn Universal Grammar (nativist)

The Case of Language Skinner – like rats Associate, imitate, repeat Trial and error learning Taught how to speak Chomsky Hard-wired for language acquisition Endowed with core rules and ability to apply those rules

The Case of Language children do learn language used in their environment, but: rate at which this happens can’t be explained by learning principles children generate all sorts of novel sentences rarely exposed to correctly formed language adults are inconsistent

The Case of Language Children apply logical grammatical rules Overgeneralizations General rules for plural forms of nouns, past tense of verbs Impose regular forms on irregular nouns/verbs

The Case of Language There are 3,628,000 ways to arrange this sentence’s 10 words. Language (even sign) just happens. Our 5000 languages are dialects of the universal grammar pre-wired in human brains.

Language Acquisition Device LA is like a box - LAD - in which grammar switches are thrown as children experience their language. English-speaking children learn to put object last (“She ate an apple.”) Japanese-speaking children learn to put object before verb (“She an apple ate.”)

Transformational Grammar Chomsky deep structure - meaning surface structure - exact wording sentences may differ in SS but convey the same DS, or vice versa

Transformational Grammar “John kicked the ball.” “The ball was kicked by John.” “Visiting relatives can be a nuisance.”

Mind as Swiss Army Knife • The human mind is the Swiss Army Knife that has all the tools. • Different species have different sets of tools.

Evolutionary Psychology