Analyzing Twin Studies and Adoption Studies Each example below provides a summary of the results research studies. Indicate if each of the following pieces of evidence support the belief that NATURE (genes) or NURTURE (life history) affects behavior: 1. A person whose identical twin has Alzheimer's is twice as likely to get the disease as someone whose fraternal twin has Alzheimer's. 2. A person whose identical twin has Alzheimer's has a 60% chance of getting the disease (not a 100% chance). 3. A person whose identical twin has divorced is 5.5 times more likely to also divorces, whereas a person whose fraternal twin has divorced in only 1.6 times more likely to also divorce. 4. Baboons who achieve higher status are physiologically healthier than those with lower status. The changes in their health appear to occur AFTER the change in status. 5. Children from impoverished environments score better on intelligence tests given at age 12 if given stimulating infant care. 6. Children raised in severely impoverish environments display stunted physical and mental growth. When placed in nurturing environments later, they exhibit a period of rapid growth. 7. Dmitry Belyaev created a breed of devoted, affectionate, and tame foxes by selectively breeding the tamest animals over 40 years. 8. In a study of 16-year-olds, the verbal abilities of adopted children more closely resembled that of their birth parents and than their adoptive parents. 9. In tests of extraversion, identical twins are more similar than fraternal twins. 10.In tests of spatial reasoning ability, the scores of identical twins correlates more strongly (=.78) than the scores of fratemal twins (r= .28) 11.Intelligence test scores tend to rise during the school year and drop in the summer. 12.Monkey infants that are original classified as uptight, stay uptight, even when placed with an easy-going mother. The same is true for easy-going monkeys placed with uptight mothers. 13.Rats in impoverished environments had thinner cerebral cortices and 20% fewer synapses than rats raised in stimulating environments. 14.Same-placenta identical twins are more similar in psychological traits than separate placenta identical twins. 15. The correlation between intelligence test scores of identical twins reared together is 0.86. The correlation between intelligence test scores of identical twin reared apart is only 0.72. The difference is statistically significant. 16.The personalities of adopted children are more like their biological parents than their adoptive parents, especially as they get older. 17.The values of adopted children are more like their adoptive parents than their biological parents. 18.When body fat in measured in adult twins, identical twins reared apart are nearly as similar to one another as identical twins reared together. The small difference between the two groups is not statistically significant. Minnesota Twin Family Study From Wikipedia, the free encyclopedia Jump to: navigation, search The Minnesota Twin Family Study (or MTFS) is a longitudinal study of twins conducted by researchers at the University of Minnesota-Twin Cities. It seeks to identify the genetic and environmental influences on the development of psychological traits. Principal investigators are David T. Lykken, Ph.D., Matt McGue, Ph.D., William Iacono, Ph.D. and Kevin Harcian, B.A. It involves several independent butrelated projects: Minnesota Twin Registry Minnesota Twin Study of Adult Development Minnesota Twin Family Study (Male Project) Minnesota Twin Family Study (Female Project) Sibling Interaction and Behavior Study Registry The Minnesota Twin Registry was established in 1983. Its original goal was to establish a registry of all twins bom in Minnesota from 1936 to 1955 to be used for psychological research. Recently, it has added twins bom between 1961 and 1964. It primarily conducts personality and interests tests with its 8,000+ twin pairs and family members via mail. From this project, it was able to confirm that twins and their families are representative of the population and that a poll of their opinions would be more accurate than polls in the newspaper. Study MTFS was established in June 1989 using same-gendered twin pairs age 11 or 17. All twins bom in MN at that time were invited to participate using birth registry data. 500 additional 11 year old twin-pairs were added in 2000. Twin studies are valuable to researchers because identical twins share 100% of their genes and fraternal twins share, on average, 50% of their genes. Both identical and fraternal twins share certain aspects of their environment (e.g religious practices in the home). This allows researchers to estimate the heritability of certain traits. Participants are asked about academic ability, personality, and interests; family and social relationships; mental and physical health; physiological measurements. Of interest to researchers are prevalence of psychopathology, substance abuse, divorce, leadership, and other traits and behaviors related to mental and physical health, relationships, and religiosity. Twins reared apart In 1979, Thomas Bouchard began to study twins who were separated at birth and reared in different families. He found that an identical twin reared away from his or her co-twin seams to have about an equal chance of being similar to the co-twin in terms of personality, interests, and attitudes as one who has been reared with his or her co-twin. This leads to the conclusion that the similarities between twins are due to genes, not environment, since the differences between twins reared apart must be due totally to the environment. Sibling interaction and behavior The Sibling Interaction and Behavior Study (SIBS) is a study of adoptive and biological siblings Since adopted siblings are not biologically related to each other or their siblings, comparing families in which two siblings are both adopted, families in which one sibling is adopted and one is biologically related to the parents, and families in which both siblings are biologically related to the parents allows environmental and biological influence to be analyzed. It additionally allows sibling influence as well as parental influence to be studied. 617 families participated in the intake phase of this study. All families consisted of two parents and two teenage siblings. The primary purposes of this study are to understand how siblings interact and influence one another, how family environment has an impact on the psychological health of adolescents, and how adoptive families are similar to and different from nonadoptive families. Adoption The Twin Study seeks to identify genetic and environmental influences on the development of psychological traits. The value of the research was the ability to estimate the inheritability of certain traits, induding academic ability, personality and interests, family and social relationships, mental and physical health, and other physiological measurements. Researchers had also studied the prevalence of psychopathology, substance use, divorce, leadership, and other traits. The relevance of the studies pertained to the importance of heredity as a determining factor in shaping our physical appearance, mental acuteness, preferences, personal characteristics, and personality. Researchers found the similarities between twins raised in separate homes with different parents to be remarkably strong. Theresearch gives significant weight to the importance of genetics as a key factor in determining physical appearance and attributes, as well as personalities and inherent abilities. This research has inferred correlations for all children raised outside their genealogical, biological, and ancestral groupings. Judith and Martin Land, (2011) Adoption Detective: Memoir of an Adopted Child, p. 96-97, 279, acknowledge The Minnesota Twin Family Study as a key reference. Children who are orphaned, fostered, or adopted may have certain behavior or inheritable traits activated by certain environmental factors or adopted parents, but only within the limitations of their genes. American public opinion, with the support of the courts, and national media attention, seek to maintain a benevolent civil approach to the raising of children that discourages profiling and prejudice. For that reason genetic and psychological research of this type is automatically rejected by some groups and individuals.