Dichotic listening asymmetry: Sex differences and menstrual cycle effects

The impact of menstrual cyclicity and sex differences on dichotic listening was studied in 25 women and 20 men (aged 20–25 years). Dichotic listening was administered using consonant-vowel (CV) stimuli and tested across three attention conditions. Women were tested at two points in the menstrual cycle (Day 2–5: low oestrogen and progesterone/Low-EP; Day 18–25: high oestrogen and progesterone/High-EP). Men were tested once. Performance averaged across attention conditions was analysed for menstrual cycle and sex effects. Significant menstrual cycle phase effects were observed in women. At the High-EP phase women showed a greater right ear advantage (REA) compared to the Low-EP phase. Sex differences were found when dichotic listening asymmetry in men was compared to women at the Low-EP, but not the High-EP phase. In contrast to laterality effects, baseline perceptual performance (total right plus left ear response) was similar in men and women at both phases of the menstrual cycle. Results support a role for ovarian hormones in shaping laterality of speech perception in women. This study also emphasises the importance of considering menstrual cycle effects when evaluating sex differences in dichotic listening.