Effects of testosterone on speech production and perception: Linking hormone levels in males to vocal cues and female voice attractiveness ratings.

This study sets out to investigate the potential effect of males' testosterone level on speech production and speech perception. Regarding speech production, we investigate intra- and inter-individual variation in mean fundamental frequency (f) and formant frequencies and highlight the potential interacting effect of another hormone, i.e. cortisol. In addition, we investigate the influence of different speech materials on the relationship between testosterone and speech production. Regarding speech perception, we investigate the potential effect of individual differences in males' testosterone level on ratings of attractiveness of female voices. In the production study, data is gathered from 30 healthy adult males ranging from 19 to 27 years (mean age: 22.4, SD: 2.2) who recorded their voices and provided saliva samples at 9 am, 12 noon and 3 pm on a single day. Speech material consists of sustained vowels, counting, read speech and a free description of pictures. Biological measures comprise speakers' height, grip strength, and hormone levels (testosterone and cortisol). In the perception study, participants were asked to rate the attractiveness of female voice stimuli (sentence stimulus, same-speaker pairs) that were manipulated in three steps regarding mean f and formant frequencies. Regarding speech production, our results show that testosterone affected mean f (but not formants) both within and between speakers. This relationship was weakened in speakers with high cortisol levels and depended on the speech material. Regarding speech perception, we found female stimuli with higher mean f and formants to be rated as sounding more attractive than stimuli with lower mean f and formants. Moreover, listeners with low testosterone showed an increased sensitivity to vocal cues of female attractiveness. While our results of the production study support earlier findings of a relationship between testosterone and mean f in males (which is mediated by cortisol), they also highlight the relevance of the speech material: The effect of testosterone was strongest in sustained vowels, potentially due to a strengthened effect of hormones on physiologically strongly influenced tasks such as sustained vowels in contrast to more free speech tasks such as a picture description. The perception study is the first to show an effect of males' testosterone level on female attractiveness ratings using voice stimuli.