Abstract
In two experiments, we explore how speaker sex recognition is affected by vocal flexibility, introduced by volitional and spontaneous vocalizations. In Experiment 1, participants judged speaker sex from two spontaneous vocalizations, laughter and crying, and volitionally produced vowels. Striking effects of speaker sex emerged: For male vocalizations, listeners’ performance was significantly impaired for spontaneous vocalizations (laughter and crying) compared to a volitional baseline (repeated vowels), a pattern that was also reflected in longer reaction times for spontaneous vocalizations. Further, performance was less accurate for laughter than crying. For female vocalizations, a different pattern emerged. In Experiment 2, we largely replicated the findings of Experiment 1 using spontaneous laughter, volitional laughter and (volitional) vowels: here, performance for male vocalizations was impaired for spontaneous laughter compared to both volitional laughter and vowels, providing further evidence that differences in volitional control over vocal production may modulate our ability to accurately perceive speaker sex from vocal signals. For both experiments, acoustic analyses showed relationships between stimulus fundamental frequency (F0) and the participants’ responses. The higher the F0 of a vocal signal, the more likely listeners were to perceive a vocalization as being produced by a female speaker, an effect that was more pronounced for vocalizations produced by males. We discuss the results in terms of the availability of salient acoustic cues across different vocalizations.
Highlights
Listeners can determine a speaker’s sex from their vocal signals with high accuracy (Coleman 1971; Lass et al 1976)
Reaction times were significantly longer for spontaneous versus volitional vocalizations, indicating greater task difficulty for sex judgements from spontaneous vocalizations. Such impaired performance for the perception of speaker characteristics has previously been reported for speaker discrimination tasks: listeners were less successful at correctly discriminating speakers from spontaneous laughter compared to volitional laughter (Lavan et al 2016b), even when this laughter was matched to volitional laughter in perceived authenticity and arousal (Lavan et al 2018a)
In the current set of experiments, we investigated whether the perception of speaker sex from non-verbal vocalizations is affected by natural vocal flexibility, introduced by using different types of vocalizations produced under different levels of volitional control
Summary
Listeners can determine a speaker’s sex from their vocal signals with high accuracy (Coleman 1971; Lass et al 1976). The perceptual cues assumed to allow listeners to distinguish male from female voices are linked to sex-specific anatomical features of the vocal tract: Due to the pronounced sexual dimorphism of the human larynx and vocal folds, males on average tend to have longer and thicker vocal folds than females, as well as longer vocal tracts (Titze 1989) These two features mainly lower the fundamental frequency of the voice (F0, broadly perceived as voice pitch) and affect the spacing of the formants in vocal signals. The salience of these cues for speaker sex identification is highlighted in a study by Mullennix et al (1995): the authors shifted F0 and formant frequencies in vocalizations and were thereby able to successfully create continua of vocalizations that were perceived by listeners to morph from male to female
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