DR Feinberg, MJ Law Smith, BC Jones, RE Cornwell, LM DeBruine, FR Moore, M Sharp, EAS Al-Dujaili & DI Perrett (2005). Diurnal shifts in testosterone predict diurnal shifts in vocal dominance in men. Human Behavior and Evolution Society in Austin, TX, USA. June 2005.

In men, testosterone (T) is positively related to aggresion, competitiveness and dominance, all of which can aid in intrasexual competition. T also positively predicts masculinity of vocal traits. Men's T is lowest in the afternoon and highest in the morning. Danger of physical altercation may be particularly acute at time characterized by hight T (e.g. morning). Men may benefit from being more perceptive of dominance cues in other men at these times as not to misjudge the dominance of others, risking physical and mental anguish, and lowered reproductive success incurred from loss in dominance bouts. We tested if men perceived masculinized voices (lowered pitch & increased vocal-tract length) as more dominant than feminized voices, and if this perceptual pattern was heightened in the morning. Masculinized voices were more dominant sounding than feminized voices. Discrimination of dominance was enhanced in the morning. Men with the largest change in T showed the largest change in attributions of dominance to men's, but not women's voices. This suggests that dominance perceptions depend on the expression of dominance in the signilar and inthe perceiver's hormonal state.

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