Diamond and Sigmundson reviewed the case by dr money in 1997 (the original study was performed in 1966) about David reimer, a boy which at eight months old was circumcised and it went terribly wrong, leading to his penis being burnt off, however this could not be fixed and under the influence of dr money 14 months later David was reassigned as female by having his testes removed and being renamed Brenda, personally I think that if any gender reassignment takes place then it should be at birth, as a pose to 22 months old.
Dr money used David Reimers case to try and prove that nurture has more of an influence than nature, initially this seemed to be the case but later on, around the age of 12 David(who was then Brenda) refused oestrogen and showed masculine traits. When Dr Money published his findings on the case he deemed it successful and said that it showed nurture over nature, although Dr Money did not publish all of his findings, the one's that may have disproved his theory he ignored and concentrated on the positive points.
Upon reviewing the case in 1997 diamond and Sigmundson announced that money's findings were wrong, as the reassignment had failed and that David had not acted in a female manner, also just before he was 16 David took male hormone treatments to reassign his gender to male, diamond and Sigmundson said that nature then prevailed over nurture.
I do think that nurture played a big part in the gender reassignment,, but not necessarily female, David may have been influenced by the behaviour of his twin brother Brian, as well as being the same age Brian would have possessed masculine toys, but also David’s parents may have pushed him too far towards femininity, causing him to rebel, his parents knew that he was born male, they may have subconsciously treated him differently to how they would treat a normal girl.
I still think that it is nature