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PSYC 2600 (183)


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PSYC 2600
Kathleen Hughes

 Human Genetics: 20, 000 genes, 46 chromosomes (23 pairs, each pair ½ from mom, ½ pair from Dad)  Politics and behavioural genetics: Nature-nurture (discounts the role of parenting, we as parents may say they are not going to try because there is a gene saying the child is not smart). Political agendas and ulterior motives (claim non-guilty for crimes because of their genes, they may take no responsibility for themselves. We may say there is no helping them and take away the guilt). Eugenics (Creating superhumans, elimination of diversity, manipulate which traits people have, using 2 positive genes to have superhumans. 2 smart people have kids and make really smart people)  Eugenics History-Started off not with people but with animals (America-horse racing and dog breeding, selective human racial betterment, better baby contests). (Britain) Lead to discrimination (races and ethnicities, immigrants, mentally retarded, felt that immigrants would dilute their pure way of life). Euthanasia and genocide (Nazi Germany, when children were born with abnormalities they would kill them to ‘save them’, they thought they were trying to purify the genetic code with genocide. Sterilization would happen if they found children were intellectually inferior they would make it so they couldn’t have kids, Alberta Sexual Sterilization Act 3000 mentally weak children, impoverish socially isolated (1920s) Benefits of Behavioural genetics  We know some traits are heavily influenced by genes: Hyperactivity and aggression (at age 2 parents say that it is just a phase; at age 8 parents say ‘always that way’) There are many failed attempts to change behaviour. Aggression can go down but the most aggressive kids always stay the most aggressive  Heritability- It is the percentage of variance attributed to genetics. (The amount of individual differences that can be attributed to genetics, cant be examined within individual but only amongst a population) Variance: amount of individual differences on a trait.  Misconceptions: Applied to individuals cannot say that 60% of you IQ is caused by parents or that 60% of differences in IQ is caused by parents. Constant only applies to a given sample not to the given environment. Precise Statistics actually are only a rough estimate (they vary based on the sample and the study etc) Behavioural Genetics Method  Family Studies: Parents trait by a child trait. Family members have more shared genes; therefore they should have more shared personality traits. Shared traits are due to genes and environment. The parents typically influence Genes and environment, brothers and sisters have shared genes because they have same parents, so we can never tell if we are studying the genetics or environmental genes. Some things run in families (familial) even if they are not genetic Twin Studies  Monozygotic (one zygote split into 2, identical twins in DNA and appearance, which is 1/3 of all twins. Mother released one egg with one sperm and the cell splits into 2)  Dizygotic (Fraternal twins, two eggs released, formed 2 zygotes. Different in appearance, DNA differences similar to difference in all siblings, but they have the shared prenatal experience which may make the personalities more similar because they are in the same environment for 9 months, 2/3 of all twins.  Monozygotic twins share 100% of the genes  Dizygotic twins share 50% of the genes (if dizygotic twins are just as similar as monozygotic then its familiar, if monozygotic twins are more similar than dizygotic twins its genetic)  To assess the heritability in twin studies: Heritability = 2(rmz-rdz). Height: Monozygotic twins (.98) dizygotic twins (.48)= 2(.98-.48)=.90  Twin studies: equal environments assumption: Monozygotic twins share the same environment, equal to dizygotic twins shared environment.  Adoption studies: Avoid equal environments assumption because they have adopted parents, they can see if they are more like their biological parent or their adopted parents. Selective placement-adoptive parents and birth parents have similarities, ethnicity, geographic region etc.  Twin Adoption Studies: it is the most powerful research method, twins that were put up for adoption and separated at birth and they didn’t interact at childhood. Representative of general population, if there are similarities we can almost say that it is from genetics.  Twin Adoption Studies: Springer twins, weird coincidences, both married and divorced women named Linda, both married a women named Betty, both had son name James, both went into carpentry, both got headaches and bit fingernails.  Daphne and Barbara: Met at 40, separated at birth, both got pregnant in the same year and had miscarriages, then had 2 boys in 1 girl and had the favorite recipe in the same recipe book.  Inheritable Traits (Imagination, aggression, neuroticism, sense of alienation, traditionalism, social potency, inhibited control, temperament, psychopathic traits- from less to the most inheritable)  Strong heritability: Raises the question of nature vs. nurture. Questions the role of parents (should we blame the mother if they are neurotic). Does that mean we don’t learn integrity, courage and tolerance (we like to think we learn them) but does it mean that they are only genetic? Good news is that none of them are 100%.  The percentage accounts for the amount of population variance that is accounted for by genetics, NOT the probability of inheriting a trait (traits are not categories, they are distributions, can be in the middle of a trait)  We can also inherit attitudes. Traditionalism, conservative attitude towards things such as death penalty, gay rights, censorship, there was a test at 12 years old with twins who were separated and they seemed to be very genetic, but it could also be because of the environment or the media, but it seemed to be more genetic.  Occupational Preferences: They didn’t find that occupations were hereditable, if not for exact job, than for job aspects, those that are important to them in their job tend to be heritable. They got kids to rate form 1- 100 what was not appealing and what was highly appealing, they were correlated to their parents (did adopted and biological). 71 signific
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