John Money's premise was that sexual identity was determined by the effects of environmental influences rather than by the genetic makeup of a person. Dr. Money felt the John/Joan case provided the perfect variables to support his hypothesis of "nature vs. nurture.".
By the time the Twin's mother had sent Dr. Money her letter, she was so desperate, she was willing to trust just about anyone who would listen to her story. Dr. Money realized how disheartened and vulnerable the mother was, and knew it would take little convincing to get her to consent to his experiment. Dr. Money basically had his work cut out for him. There, in front of him, were two healthy identical twin boys, being raised by the same two parents, in the same environment. If John's transformation to Joan was successful, it would be the direct result of nurturing and not nature because the twin's genetic makeup and atmosphere were the same at the beginning. Dr. Money would manipulate John/Joan's genitalia and insist this be the twin that was raised as if he were born female. Money did not manipulate Kevin's body or change the environmental influences he would normally be exposed to as a male. .
Dr. Money was known as an outspoken, overly confident researcher. The John/Joan situation provided Dr. Money with an opportunity to establish himself as a pioneer in the area of sexual research, while supporting his nature vs. nurture hypothesis.
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