Males and females are known to be significantly different in regard to their performance on dichotic listening tests with males typically demonstrating a larger Right Ear Advantage (REA) for verbal stimuli (Govier & Bobby 1994; Lake & Bryden 1976; McGlone & Davidson 1973; Wexler & Lipman 1985).
We administered dichotic listening tests to more than 50 male-to-female transsexuals and 15 female-to-male transsexuals as well as comparable groups of controls. In these tests 60 pairs of consonant vowel consonant (CVC) syllables (e.g., kib and tib) were presented, one syllable to each ear simultaneously, via earphones and the respondent asked which syllable or syllables were heard?
Our findings showed persons with the M2F condition produced a response pattern which was significantly different from typical males (p <.05). There was no significant correlation between time on gender appropriate hormone treatment and dichotic performance. There is no evidence we know of where this group difference might be due to other environmental or learning factors. This is suggestive of actual brain “hard-wired” differences among M2F transsexuals when compared to typical males; their dichotic performance is more in keeping with their gender than with their sex. So far we have found no comparable sex/gender differences among our F2M subjects. We are currently enlarging our samples.