<P> The Minnesota Twin Registry was established in 1983 . Its original goal was to establish a registry of all twins born in Minnesota from 1936 to 1955 to be used for psychological research . Recently, it has added twins born 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 . </P> <P> MTFS was established in June 1989 using same - gendered twin pairs age 11 or 17 . All twins born 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 . It has received funding from the Pioneer Fund and the Koch Foundation . </P> <P> In 1979, Thomas J. 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 seems 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 . Psychologist now refer to studies such as this as an Adoption Strategy . </P>

Primary finding of the minnesota study of twins reared apart