SEX-DIFFERENCES IN THE AUDITORY-SYSTEM

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 latencie s in their auditory brain-stem responses, more spontaneous otoacoustic emissions (SOAEs), and stronger click-evoked otoacoustic emissions th an males as a group. Males are better at sound localization, detecting binaural beats, and detecting signals in complex masking tasks than a re females. During the first half of the menstrual cycle, several aspe cts of female hearing move in the male direction. The sex difference n ormally present in SOAEs is absent in females from opposite-sex twin p airs. The implication is that their auditory systems have been masculi nized prenatally by exposure to high levels of androgens produced by t heir male cotwins, analogous to an effect well established in other ma mmals. This suggests that some of the other sex differences in hearing are also attributable to differences in exposure to hormones. Thus, t he SOAE findings suggest an organizational effect of hormones on the h uman auditory system, and the menstrual findings suggest an activation al effect. Said differently, the auditory system appears to be among t hose brain structures that are altered by hormones pre- and postnatall y, implying that some auditory measures may eventually prove valuable as windows onto other hormone-driven processes, characteristics, and a bilities.