 However, he believed that boys would lose this desire as long as his parents set limits when raising him, or he had the right genetic predispositions or a normal sexuality.Harry Benjamin considered the causes of transsexuality to be badly understood, and argued that researchers were biased towards considering psychological causes over biological causes.Ray Blanchard has developed a taxonomy of male-to-female transsexualism built upon the work of his colleague Kurt Freund, which assumes that trans women have one of two motivations for transition.