ABSTRACT
A number of sex differences have been documented in the human auditory system. Females as a group have greater hearing sensitivity, greater susceptibility to noise exposure at high frequencies, shorter latencies in their auditory brain-stem responses, more spontaneous otoacoustic emissions (SOAEs), and stronger click-evoked otoacoustic emissions than males as a group. Males are better at sound localization, detecting binaural beats, and detecting signals in complex masking tasks than are females. During the first half of the menstrual cycle, several aspects of female hearing move in the male direction. The sex difference normally present in SOAEs is absent in females from opposite-sex twin pairs. The implication is that their auditory systems have been masculinized prenatally by exposure to high levels of androgens produced by their male cotwins, analogous to an effect well established in other mammals. This suggests that some of the other sex differences in hearing are also attributable to differences in exposure to hormones. Thus, the SOAE findings suggest an organizational effect of hormones on the human auditory system, and the menstrual findings suggest an activational effect. Said differently, the auditory system appears to be among those brain structures that are altered by hormones pre- and postnatally, implying that some auditory measures may eventually prove valuable as windows onto other hormone-driven processes, characteristics, and abilities.
