Purpose As children mature, changes in voice spectral characteristics covary with changes in speech, language, and behavior. Spectral characteristics were manipulated to alter the perceived ages of talkers’ voices while leaving critical acoustic-prosodic correlates intact, to determine whether perceived age differences were associated with differences in judgments of prosodic, segmental, and talker attributes. Method Speech was modified by lowering formants and fundamental frequency, for 5-year-old children’s utterances, or raising them, for adult caregivers’ utterances. Next, participants differing in awareness of the manipulation (Exp. 1a) or amount of speech-language training (Exp. 1b) made judgments of prosodic, segmental, and talker attributes. Exp. 2 investigated the effects of spectral modification on intelligibility. Finally, in Exp. 3 trained analysts used formal prosody coding to assess prosodic characteristics of spectrally-modified and unmodified speech. Results Differences in perceived age were associated with differences in ratings of speech rate, fluency, intelligibility, likeability, anxiety, cognitive impairment, and speech-language disorder/delay; effects of training and awareness of the manipulation on ratings were limited. There were no significant effects of the manipulation on intelligibility or formally coded prosody judgments. Conclusions Age-related voice characteristics can greatly affect judgments of speech and talker characteristics, raising cautionary notes for developmental research and clinical work.

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Previous research in small-N studies has indicated conflicting findings regarding whether mothers modify voice-onset time (VOT) of wordinitial stop consonants in speech to infants compared to speech to adults, as well as the nature of any such modification. In a large-scale study, VOT was measured for voiced and voiceless stop consonants in speech of 48 mothers of infants in one of four cross-sectional age groups (0;3, 0;9, 1;1, 1;8) when they read a phonetically-controlled storybook to their infant (ID speech) or an adult (AD speech). VOT measurements showed enhanced clarity (i.e., longer VOTs) in ID speech compared with AD speech for voiceless stop consonants only. An effect of infant gender was also found, showing that enhanced clarity was only produced by mothers of female infants (N = 19). Infant age was not found to be a significant factor in VOT production. The results have implications for understanding the nature of linguistic development in young children, specifically by elucidating factors apparently related to phonetic modification for clarity, including speech style and gender. Work supported by NIH-NIDCD grant R01DC008581.

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