Beyond the linguistic content of their speech, speakers of both sexes convey diverse biological and psychosocial information through their voices, which are important when assessing potential mates and competitors. However, studies investigating the relationships between mating success and acoustic inter-individual differences are scarce. In this study, we investigated such relationships in both sexes in courtship and competitive interactions-as they correspond to the two different types of sexual selection-using an experimental design based on a simulated dating game. We assessed which type of sexual selection best predicted mating success, here defined as the self-reported number of sexual partners within the past year. Our results show that only acoustic inter-individual differences in the courtship context for both men and women predicted their mating success. Men displaying faster articulation rate and louder voices reported significantly more sexual partners; in contrast, men displaying higher intonation reported a greater negative effect of roughness and breathiness on their mating success. Women who displayed relatively less breathy voices and shorter speech duration reported significantly fewer sexual partners. These novel findings are discussed in light of the mate choice context and the relative contribution of both types of sexual selection shaping acoustic features of speech.

Potential differences between homosexual and heterosexual men have been studied on a diverse set of social and biological traits. Regarding acoustic features of speech, researchers have hypothesized a feminization of such characteristics in homosexual men, but previous investigations have so far produced mixed results. Moreover, most studies have been conducted with English-speaking populations, which calls for further cross-linguistic examinations. Lastly, no studies investigated so far the potential role of testosterone in the association between sexual orientation and speech acoustic features. To fill these gaps, we explored potential differences in acoustic features of speech between homosexual and heterosexual native French men and investigated whether the former showed a trend toward feminization by comparing theirs to that of heterosexual native French women. Lastly, we examined whether testosterone levels mediated the association between speech acoustic features and sexual orientation. We studied four sexually dimorphic acoustic features relevant for the qualification of feminine versus masculine voices: the fundamental frequency, its modulation, and two understudied acoustic features of speech, the harmonics-to-noise ratio (a proxy of vocal breathiness) and the jitter (a proxy of vocal roughness). Results showed that homosexual men displayed significantly higher pitch modulation patterns and less breathy voices compared to heterosexual men, with values shifted toward those of heterosexual women. Lastly, testosterone levels did not influence any of the investigated acoustic features. Combined with the literature conducted in other languages, our findings bring new support for the feminization hypothesis and suggest that the feminization of some acoustic features could be shared across languages.