Vocal production mechanisms in a non-human primate: Morphological data and a model

Institut für Theoretische Biologie, Humboldt-Universität zu Berlin, Invalidenstrasse 43, 10115 Berlin, Germany.
Journal of Human Evolution (Impact Factor: 3.73). 02/2005; 48(1):85-96. DOI: 10.1016/j.jhevol.2004.10.002
Source: PubMed


Human beings are thought to be unique amongst the primates in their capacity to produce rapid changes in the shape of their vocal tracts during speech production. Acoustically, vocal tracts act as resonance chambers, whose geometry determines the position and bandwidth of the formants. Formants provide the acoustic basis for vowels, which enable speakers to refer to external events and to produce other kinds of meaningful communication. Formant-based referential communication is also present in non-human primates, most prominently in Diana monkey alarm calls. Previous work has suggested that the acoustic structure of these calls is the product of a non-uniform vocal tract capable of some degree of articulation. In this study we test this hypothesis by providing morphological measurements of the vocal tract of three adult Diana monkeys, using both radiography and dissection. We use these data to generate a vocal tract computational model capable of simulating the formant structures produced by wild individuals. The model performed best when it combined a non-uniform vocal tract consisting of three different tubes with a number of articulatory manoeuvres. We discuss the implications of these findings for evolutionary theories of human and non-human vocal production.

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Available from: Klaus Zuberbühler
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    • "Thus, the sagittal distances measured in our three anaesthetized Diana monkeys are likely to represent a reasonable estimate of the area function of the monkeys' vocal tract. Nevertheless, we agree with Lieberman that more sophisticated techniques capable of documenting the vocal tract changes in vocalizing animals are desirable for future studies (Riede et al., 2005). "
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    ABSTRACT: Male West African Diana monkeys (Cercopithecus diana) produce acoustically distinct alarm calls to two of their main predators, the crowned eagle and the leopard. The calls are re-markable in their acoustic structure for at least three reasons. First, they exhibit clear formant frequencies, a defining feature of human speech. Second, Diana monkeys are able to modify the basic structure of these formants by creating formant tran-sitions. In leopard alarm calls, the first formant describes a transition of approximately 150 Hz, while the transition of the second one is about 200 Hz. In striking contrast, the two formants remain relatively constant in eagle alarm calls (Riede and Zuberbühler, 2003a,b). Experiments have shown that these acoustic differences have semantic value to recipients (Zuber-bühler, 2003). Third, the first and second formants in Diana monkeys' alarm calls are in close proximity, a feature not nor-mally observed in animal vocalizations. We propose that this formant proximity is the result of a discontinuity (or 'non-uni-formity') along the monkey's vocal tract. In a previous paper (Riede et al., 2005), we sought to un-derstand the production mechanisms of the Diana monkey vocal system using a computer modelling technique, based on anatomical data. Lieberman (2006) has challenged a num-ber of our findings. His concerns relate to the possibility of tongue movements, pharyngeal constrictions, and the posi-tion of the larynx. Additionally, the technique of deriving vocal tract area functions from lateral x-rays is criticized. We would like to respond to these criticisms by first sum-marizing our main point, the notion of non-uniform vocal tracts in nonhumans, before responding in detail to Lieber-man's critique.
    Full-text · Article · Oct 2014 · Journal of Human Evolution
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    • "More recent studies have suggested that mammalian vocal tracts are in principle capable of producing speech sounds, suggesting that limitations are more likely at the neural and not the anatomical level (e.g. Fitch & Zuberbühler, 2013 ; Riede, Bronson, Hatzikirou, & Zuberbühler, 2005 ) although little is known about the actual dynamics of primate vocal tracts during vocalisation (de Boer & Fitch, 2010 ; Fitch, 2000 ). An unresolved problem is what genetic changes during human evolution have led to greater motor control of the vocal tract in humans. "
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    ABSTRACT: How did human language evolve from earlier forms of primate communication? One key transition has been increased motor control during vocalisation, which enables humans to generate and imitate complex vocal patterns. Although humans are unique in this way, evolutionary inventions are usually modifications of earlier adaptations. The purpose of this chapter thus is to survey the recent primate literature for evidence of vocal control. To this end, we are interested in two qualities, acoustic variants of basic call types and call sequences. We find evidence for both in different species of primates, suggesting a direct transition from primate vocal behaviour to human speech. Future research will have to focus on the mechanisms of motor control of the speech-relevant articulators, particularly the larynx, velum, tongue, and lips. © 2014 Springer Science+Business Media New York. All rights are reserved.
    Full-text · Book · Jan 2014
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    • "Human sopranos change the mouth opening to move F 1 in synchronization with f 0 as the latter changes. The vocal apparatus moves flexibly during vocalizations in nonhuman primates (Fitch, 2000b; Riede et al., 2005) rather than remaining static as previously thought (Lieberman et al., 1969), and gibbons indeed open their mouths wider in synchrony with rising pitch (Haimoff, 1984). Furthermore, gibbons might voluntarily regulate movements of their vocal apparatus to perform such synchronized movements (e.g., through the audio feedback ). "
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    ABSTRACT: Diversifications in primate vocalization, including human speech, are believed to reflect evolutionary modifications in vocal anatomy and physiology. Gibbon song is acoustically unique, comprising loud, melodious, penetrating pure tone-like calls. In a white-handed gibbon, Hylobates lar, the fundamental frequency (f(0) ) of song sounds is amplified distinctively from the higher harmonics in normal air. In a helium-enriched atmosphere, f(0) does not shift, but it is significantly suppressed and 2f(0) is emphasized. This implies that the source is independent of the resonance filter of the supralaryngeal vocal tract (SVT) in gibbons, in contrast to musical wind instruments, in which the filter primarily determines f(0) . Acoustic simulation further supported that gibbons' singing is produced analogously to professional human soprano singing, in which a precise tuning of the first formant (F(1) ) of the SVT to f(0) amplifies exclusively the f(0) component of the source. Thus, in gibbons, as in humans, dynamic control over the vocal tract configuration, rather than anatomical modifications, has been a dominant factor in determining call structure. The varied dynamic movements were adopted in response to unique social and ecological pressures in gibbons, allowing monogamous gibbons to produce pure-tonal melodious songs in the dense tropical forests with poor visibility. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.
    Full-text · Article · Nov 2012 · American Journal of Physical Anthropology
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