Research ArticleHUMAN EVOLUTION

Monkey vocal tracts are speech-ready

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Science Advances  09 Dec 2016:
Vol. 2, no. 12, e1600723
DOI: 10.1126/sciadv.1600723

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  • Yawning at the dawn of speech: Response to Fitch et al. (2016)

    This innovative study undoubtedly advances our understanding of primate vocal tracts. Yet it seems premature to conclude, as the authors have, that monkey vocal tracts could “easily” produce the requisite range of sounds for human-like speech. Their analysis is based in large measure on 3 vocal tract configurations (of 99), utilized while a macaque was yawning. (The 3 rightmost dots in Figure 2.) These configurations, with maximal/near-maximal jaw lowering, are what enable the macaques’ theoretical production of a “low” vowel. In contrast, humans produce all peripheral vowels, including the high front vowels the macaques cannot produce, with minimal jaw movement. So it remains unclear just how easily macaque vocal tracts could produce peripheral vowels that play a major role in speech. The study fruitfully shows that, with extensive mandibular lowering, monkeys could produce a greater range of formants than typically assumed. This is an important finding, but it should be concomitantly stressed that humans naturally produce all peripheral vowels with comparatively minor vocal tract modulation. While these novel data may shift the debate about vocal-tract speech-readiness, they do not resolve it. (For a closer look at the study’s ramifications to our knowledge of formant spaces, see: http://calebeverett.weebly.com/uploads/4/2/6/5/4265482/commentary_on_fit....)

    Fitch et...

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    Competing Interests: None declared.