Define and describe the uses for and limitations of family studies, twin studies, and adoption studies. What has been learned from these studies about the role of heredity in shaping human personality?

Family studies look at heritability based on the assumption that if genes influence a certain trait, close relatives should be more similar on the trait than distant relatives. This type of study has been used to look at the likelihood of schizophrenia, and whether it is genetically linked (since closer family members are more likely to have the disorder). Twin studies look at identical versus fraternal twins to determine whether nature (genetics, which identical twins share) influences behavior and personality more than nurture (which fraternal twins share similar to identical twins, but their genetic makeup is no closer than other siblings). Adoption studies look at children adopted at birth by parents not related to them to see the effect of nurture (environment) versus heredity (genetics) on behavior. All three methods look at teasing apart the influences of heredity and environment.