The fact is that we don't know enough about hormonal effects on the human brain to have a very specific theory of how Danny's brain could have develo… - J. Michael Bailey

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The fact is that we don't know enough about hormonal effects on the human brain to have a very specific theory of how Danny's brain could have developed in a feminine direction while his body developed masculine. If Danny's body also showed signs of feminine development, this would support nature theory, but the lack of anatomical femininity does not disprove it. There has been essentially no research on boys like Danny that is directly biological. Short of dissecting the brain of a feminine boy and comparing it with normal boys' and girls' brains, it is unclear what we would even look for. However, the best conceivable direct test of nurture theory has been tried, and it failed. Amanda became Jason again.