The development of sex/gender-specific /s/ and its relationship to gender identity in children and adolescents

A growing body of literature has revealed sex/gender differences in the acoustics of the sibilant fricative /s/. It has been suggested that some of this sex/gender-related variation might be socially motivated and acquired. However, the necessary developmental research to corroborate this proposal is absent from the literature. To address this, we examined sex/gender differences in the production of /s/ acoustics in relation to children׳s physical growth and gender identity. The speech production of children and adolescents aged 4-16 years old was recorded. Additionally, the physical height was measured and gender identity was evaluated through a parent-filled questionnaire. Three acoustic measures were calculated that describe the mean, standard deviation, and skewness of the spectral frequencies of /s/. Results indicated that gender identity played a key role in mediating the difference in /s/ acoustics between boys and girls for all three acoustic measurements. Additionally, for adolescent boys, gender identity explains within-gender variation in /s/. Our results thus highlight the importance of social-behavioral factors in the development of sex/gender difference in /s/ production.