Researchers are still trying to find out what matters more -- our genes or our environment -- when it comes to making choices in what we like to eat, who we prefer to love and how smart we will be.
Researchers have found that one way to get a better idea about the impact on genes on everything from ability in mathematics to a predisposition for breast cancer is to study twins.
The separation of twins gives scientists an ability to really examine nurture versus nature.
So far, however there has been only one study that looked at separate twins from their infancy through adulthood. The results of that study will not be released until 2066.
During the 1960s, 1970s and 1980s, Peter Neubauer, a child psychiatrist and Viola Bernard, a child psychologist, led a study in which twins and triplets given up for adoption at a New York adoption agency were separated and studied throughout their lives.
When the babies were placed with their respective families, the parents were told the child was part of ongoing research that would require interviews and evaluations, but were not told that the child was a twin or a triplet. They also were not told that the research involved nature versus nurture.
In 1981, New York state began requiring that siblings be kept together in the adoption process. Neubauer realized the public might not be receptive to a study that used the separation method, so the results were sealed and placed at Yale University. The results will not be opened until 2066.
While the results have not been released, Bernstein and Schein say it's undeniable that genetics play a major role. Bernstein has put the number at more than 50 percent.