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May 30th Lecture.docx

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PSYC 2130
Krista Phillips

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Lecture 7 *** Correction from pervious lecture: The pain tolerance for extravert was stronger than for introverts. Midterm #2  Five chapters 14 items from each chapter and 15 item from lecture = 85 question  Don‟t need to know specific anatomy, or hormones, but know the main ones i.e. know stress hormones, and know the brain areas by function  Know: Patel, Allport, etc  Know theorists by what they proposed  There is a question on the twins film  Know the first chunk of chapter 7 there are hormone and neurotransmitter questions 1. Methods in Behaviour Genetics genetic factors play significant role in personality and there is evidence for this through empirical studies. When behaviour genetics became to emerge there was enormous reluctance to embrace these data, which are relatively new. There was a huge backlash movement. Strong opposition to idea of evidence for genetic influence on any psych trait. We accept genetic basis for medical conditions (i.e. breast cancer). 1. Immutable – unchangeable. We are uneasy when we know: a psychological trait or personality trait has genetic predisposition. It makes us feel powerless- if under genetic control, it is somehow Unchangeable, threatens individuality, freedom – this is incorrect. it clashes with our philosophy of free will; we have been socialized to think. 2. That babies come into world as blank slates, and experiences form who we are – this was the central position until recently. Example: preference for sweet food is genetic. 3. This assumption is wrong because the trait can be modified by environment and learning. Love, sex, intimate relationships are genetically programmed (mating preferences). Women want: IQ, health, money, humor. Men: loyalty, youth, IQ, attractiveness.  Selective Breeding the thought of selecting a mate had genetic factors is crazy. For female choosing a mate some of the things that is important to them is: IQ, sense of humor, recourses, fitness, kindness, confidence, ambition, and loyalty. Men want for a long-term partner: attractiveness, sense of humor, youth, health, sexual loyalty, nurturing. Mating is not random in our species  Inbreeding  Analogues “experiments” with humans Buss asked: what do you want in a mate? And he found the same consistent list  Males are wired to be continuously receptive to reproductive opportunities  Males have more opportunities than females to mate  Females are more choosy, because they invest much more energy in one egg, and have less potential Buss’s sexual jealousy questionnaire  Which is worse? A) Discover that your partner is having sex w/ another person or B) you discover that your partner is involved in a deep emotional relationship with another person o A is common male response, B is common female response o The male has uncertainty if the resources is he investing is actually for his own offspring or some one else‟s thus: some of the decisions we make have evolutionary basis The current question: How much is the relative contribution of genetic and environmental factors They are interested in: individual differences and degree to which genes and environment contribute to these differences- behavioural genetics tell us just as much abt role of env as genes 2. Heritability of Personality Traits 3. Data on MZ vs. DZ Twins 4. Shared vs. Unshared Sources of Variation 5. Critical Analysis Methods in Behaviour Genetics Heredity Environment Selective Breeding Varies Constant Inbreeding Constant Varies Human Analogies 1. Identical Twins Reared Together 2. Identical Twin Reared Together vs. Fraternal Twins Reared Together 3. Identical Twins Reared Apart Heritability – V p V g H = r. identical twins reared apart H = (rid r frX 2 Lecture: Methodologies – research w animals  Field of behaviour genetics started in animal research, w less ethical issues  Most behavioural geneticists use a variation of these 2 methods o With animals, we can selectively breed for traits (ex. Aggression) by:  1) Forcing animals high on trait to mate, and those low on trait on that o This done over generations give aggressive and passive mice o Then rear them in identical environments o We then compare aggressive and passive mice; if “aggressive” mouse is more aggressive than “passive”, we say aggression is hereditary  2) Can have mice inbreed (w parents or sibling) – heredity is constant o Both are reared the same, except one group of mice has practice in T maze o If one group outperforms the other, the ability was learned – environment was varied Research with Humans  Due to ethical issues, we cannot breed humans; instead, we have other methods: 1) Twins/sibs reared together:  Identical twins raised together, given a shyness questionnaire, we get r= +0.55 o This strong association might come from: shared genes or shared environment or mixed role  Fraternal twins (50% similar), they are raised together, r= +0.45  Here, we can say there is a role of genetics in development of shyness, because similarity between identical and fraternal twins  This is the human analogy for selective breeding 2) Twins/ siblings reared apart:  Especially identical twins reared together  Genetics are 100% same, but environment are completely different  This is replacement for inbreeding Heritability  Qualitatively developed method  Ratio of phenotype (the expressed characteristics) variance attributable to genotype (your own genetic) variance (how much of phenotype variance is due to genotype) 2 heritability (h ) = p /g i.e. phenotype: blue eyes; genotype: bb (two recessive genes)  you could not tell the genotype of a brown-eyed person, however. Could be BB, Bb, bB simples index of heritability:  H= r. identical twins reared apart (correlation of identical twins reared apart) o =Direct representation of heritability because identical twins that are separated at birth typical are raised in a similar environment o -Have to assume their environments are not correlated this correlation coeffient will give you a directed representation of heritability. o This is not always the case, because twins reared apart actually have environments that are similar o If environments are not correlation, this coefficient gives an inflated over- estimated of heritability (“r” overestimates genetic influences) unless abs certain that the envs were not correlated, your r will be over-estimated thus, instead, geneticists use: H= 2(r idr fr comparing identical twins reared together vs. fraternal twins raised together. This will give us a more reasonable prediction of heritability  Twin studies are part of method used by behavioural psychologist  IQ has highest heritability  Heritability of IQ increase as subjects get older: from middle childhood to adulthood  This heritability is not constant  The heritability is not a static number o The heritability of IQ, your IQ is determined by your IQ  As adopted children get older, their resemblance to bio parents in IQ increases and become less similar in IQ to adopted parents  Because some genes are expressed/ manifest later on in life, by environmental factors  ***For most personality traits, heritability is between r= 0.4-0.5 – this is very strong o This was a surprise: that genes play important role in also every personality trait Plomin and Daniels (1987) ***Reviewed all of behaviour genetics data and came up with a remarkable conclusion:  When you look at correlation coefficient for identical
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