EXAM 1: LECTURE NOTES UP TO WEEK 5 (I.E. INCLUDING THIS LECTURE)Behavior Genetic Methods:a.Inbred stainsb.Selective breedingA.Animal StudiesB.Family StudiesC.Twin StudiesD.Adoption StudiesSelective breeding:•Selective breeding (also called artificial selection) is the process by which humans breed other animals and plants for particular traits.•e.g.Get a large group of animals that are extreme in some trait, and then you breed. Then you choose their children, select ones that are extreme on some trait, and so on.•As an example if you take a group of rats, and breed only the intelligent ones, over a course of time, the least intelligent of this breed will still be higher in intelligence than the most intelligent rats that were not subjected to such breeding techniques. Advantages of animal studies:1.Almost any kind of behavior can be studied relatively easily (especially from a research perspective).2.The construct of "different genotypes, identical environments", can be easily met. 3.We can observe how differences in traits/behaviors change over generations (animals have a shorter life span), and thus make estimations of the degree of these differences (no effect, little effect, large effect).Disadvantages of animal studies:1.No matter what you're looking at, it is almost invariably more simple, than what you're really interested in. e.g. Psychologist do not care about rats making a wrong turn in a maze. What they do care, is human intelligence. In order to better understand human intelligence, they may have to study rats making a wrong turn in a maze. This is more simple than what you're really interested in (i.e. human intelligence). Thus, studying rats is relevant, but that's not really the whole story. 2.Compared to human behavior, almost by definition, all other animal behavior is more instinctual in nature, and perhaps more genetically programmed. ○A fertilized egg (zygote) has 23 pairs of chromosomes. Each of those chromosomes has thousands of genes. We share those genes to different degrees with different relatives. ○For identical twins, 100% of the genes are common b/w each sibling. ○First degree of relatedness: 50% of genes in common with brothers, sisters, parents, children○Second degree of relatedness: 25% of genes shared with each of our grandparents, grandchildren, uncles, aunts, half-brothers/sisters.○Third degree of relatedness: 12.5% of genes in common with cousins.○Fourth degree of relatedness: 6.25% of genes in common with second cousins. i.We should find phenotypic similarity among blood relatives;ii.We should find more similarity among those who share more genes in common, and find less similarity among those who have fewer genes in common (e.g. more similarity b/w children and parents, than children with grandparents). ○The logic of family studies suggests that if heredity affects a given trait, then 2 things should be true: ○E.g. It has been suggested that Schizophrenia has a genetic basis. If you have a cousin who has been diagnosed with schizophrenia, the probability that you will be diagnosed a schizophrenic goes up to about 2%. If you have a grandparent who has been diagnosed with schizophrenia, the probability that you will be diagnosed with schizophrenia goes up to 3%. If you have a first degree of relatedness with someone who is a schizophrenic (e.g. your mother), the probability that you will be diagnosed with the same mental illness goes up by 8%.•Genetic relatedness:○Families not only share genes, but also environment. Close relatives tend to have more similar environments than distant relatives. •Conceptual problems with this theory: Refuting the claim that behaviors/traits/phenotypic similarities are 100% due to genes:FAMILY STUDIES:Week 5.0 Psych 100 Tuesday, September 24, 20132:00 PM Week 5.0 Psych 100 Page 1○Close relatives tend to have more similar environments than distant relatives. 1.Monozygotic twins("Identical twins"): Come from situations that are statistically unlikely, but they do occur. One fertilized egg splits apart and replicates itself in the womb. Thus, because they come from 1 fertilized egg, they have 100% genes in common. 2.Dizygotic twins("Fraternal twins"): Also statistically unlikely. Two eggs get fertilized from two different sperms, but are conceived at the same time. Because they come from 2 zygotes, they have 50% genes in common. Both kinds of twins have identical environments from birth - both are exposed to similar family structures, and social-economic-cultural settings. TWIN STUDIES:Drawing inferences:a.The correlation b/w fraternal twins is not zero. These twins have 50% of genes in common. These 2 fraternal twins resemble each other in terms of mental abilities much more than those in the general population. b.The correlation for fraternal twins is not nearly as high as for identical twins (which is 0.85). Thus, the identical twins resemble each other to a much greater degree than fraternal twins. Q.What inferences can we draw from this? E.g. Let us say that the correlation b/w identical twins on general mental abilities is 0.85. The correlation b/w fraternal twins is 0.6.Therefore, we conclude, that there is a genetic component underlying general mental abilities. IDENTICAL TWINSFRATERNAL TWINSBoth siblings are of the same genderThe siblings may be of different genders.Stereotypical notions are held constant for both siblings. i.e. the environment is more or less the same for both siblings.Sterotypical notions manipulate the environment to which different genders are subjected (e.g. a boy may be seen as more "useful" to the family than a girl , altering the environment of the boy and the girl).100% genes in common50% genes in common : thus, they are more likely to differ from each other than identical twins. Elicit similar parental reactionsMay elicit different parental reactions (e.g. 1 baby cries while the other sleeps, so the parent has to attend to only the baby that cries).ADOPTION STUDIES:Such studies examine the degree to which adopted children resemble the adopted parents, and the degree to which adopted children resemble the biological parents.Key: c-> child; bio->biological mother (whom the child has never met); adopt->adoptive mother; rho=correlationPlausible outcome:Rho (c, bio) > rho (c, adopt) suggesting evidence for a genetic componentDISCUSSION:Is intelligence largely genetically determined, or is it largely due to environmental factors?To answer this, we can