Abstract
BackgroundIt is usually possible to identify the sex of a pre-pubertal child from their voice, despite the absence of sex differences in fundamental frequency at these ages. While it has been suggested that the overall spacing between formants (formant frequency spacing - ΔF) is a key component of the expression and perception of sex in children's voices, the effect of its continuous variation on sex and gender attribution has not yet been investigated.Methodology/Principal findingsIn the present study we manipulated voice ΔF of eight year olds (two boys and two girls) along continua covering the observed variation of this parameter in pre-pubertal voices, and assessed the effect of this variation on adult ratings of speakers' sex and gender in two separate experiments. In the first experiment (sex identification) adults were asked to categorise the voice as either male or female. The resulting identification function exhibited a gradual slope from male to female voice categories. In the second experiment (gender rating), adults rated the voices on a continuum from “masculine boy” to “feminine girl”, gradually decreasing their masculinity ratings as ΔF increased.Conclusions/SignificanceThese results indicate that the role of ΔF in voice gender perception, which has been reported in adult voices, extends to pre-pubertal children's voices: variation in ΔF not only affects the perceived sex, but also the perceived masculinity or femininity of the speaker. We discuss the implications of these observations for the expression and perception of gender in children's voices given the absence of anatomical dimorphism in overall vocal tract length before puberty.
Highlights
Adults can discriminate the sex of adult [1] and of children [2,3] speakers by listening to their voice only
Sex identification in adult voices is substantially determined by acoustic differences in fundamental frequency (F0) and in the overall pattern of formant frequencies (DF, or formant spacing), which in turn reflect anatomical dimorphisms in the vocal apparatus between the two sexes
The results of the sex identification and gender rating experiments show that DF is an important cue for the perception of sex and gender in the pre-pubertal human voice, in line with the previously reported acoustic dimorphism of this parameter in prepubertal speakers [8,14,17,32]
Summary
Adults can discriminate the sex of adult [1] and of children [2,3] speakers by listening to their voice only. Several acoustic investigations have shown that, while children of both genders speak with similar F0s ([13,14,15]; and see [16]) boys speak with lower formants and narrower DF than girls [2,3,13,14,17,18] despite the absence of overall differences in vocal tract length between the two sexes before puberty [10,19,20,21] This dimorphism has led to the suggestion that pre-pubertal sex differences in DF have a behavioural basis (for example boys may round their lips or lower their larynx when they speak to lengthen their vocal tracts – [2,14]). While it has been suggested that the overall spacing between formants (formant frequency spacing - DF) is a key component of the expression and perception of sex in children’s voices, the effect of its continuous variation on sex and gender attribution has not yet been investigated
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