Dichotic Listening, Handedness, Brain Organization, and Transsexuality

This study investigated the functional brain organization of 68 male-to-female (MtF) transwomen and 26 female-to-male (FtM) transmen by comparing their performance with 36 typical male and 28 typical female controls on two indicators of cerebral lateralization: dichotic listening and handedness. A sex-differentiating dichotic test and a handedness questionnaire were administered. It was hypothesized that the MtF participants' dichotic performance would be significantly different from the control males and resemble the control female pattern. This hypothesis was supported. It was also hypothesized that the FtM dichotic pattern would be significantly different from the control females and would resemble the control male pattern. This hypothesis was not supported. Finally, it was hypothesized that there would be significantly more nonexclusive right-handers in both trans-groups. This hypothesis was supported. Taken together, the dichotic and handedness data reported here indicate that the MtF and FtM conditions are not mirror images in terms of the verbal-auditory aspects of their brain organization and neurobiology plays an important role, particularly in the development of the male-to-female trans-condition.