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

Abstract

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. Formantbased 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 nonhuman vocal production.

Vocal Tract Morphology Determines Species-Specific Features in Vocal Signals of Lemurs (Eulemur)

“…Formants were not uniformly distributed in lemurs. This is not the first evidence of nonuniform vocal tract shapes in nonhuman primates (Fitch 2000;Riede et al 2005), but it is particularly interesting because it is in agreement with results for Varecia variegata (Gamba and Giacoma 2006). The role of F1 is particularly important, as in most species F2 is around twice F1, while F3 and F4 are around twice and three times F2, respectively.…”

“…Two studies have used computational models to show that spectral prominences of nonhuman primate vocalizations were formants (Cercopithecus diana: Riede et al 2005;Varecia variegate: Gamba and Giacoma 2006). However, the explanatory potential of applying models of vocal production is limited by the lack of knowledge concerning the anatomy and dynamics of vocal tracts (de Boer and Fitch 2010).…”

The evolution of speech and language

“…Darwin (1871), in his book The Descent of Man, proposed the idea that language appeared by imitation and modification of different sounds from nature and special human sounds, and that it was supported by gestures and favored natural (sexual) selection. Many agree with his idea and emphasize the advantage of sounded spoken language as proof of vocalized beginnings of language (Tomasello 2008;Riede et al 2005;Zuberbühler 2005;Hewes 1973), while comparative studies of primates serve as a basis for the gestural theory (Corballis 2009Goldin-Meadow & McNeill 1999). The first and basic step in studying language in prehistory is to define the term language itself.…”

“…je u djelu O podrijetlu čovjeka predložio kako je jezik nastao iz imitacije i modifikacije različitih zvukova iz prirode te posebnih ljudskih povika, potpomognut znakovima i gestama i favoriziran prirodnim (spolnim) odabirom. Mnogi se slažu s tom pretpostavkom te ističu prednosti zvučno-ga govorenoga jezika kao dokaze vokalnih jezičnih početaka (Tomasello 2008;Riede et al 2005;Zuberbühler 2005;Hewes 1973), dok se komparativna istraživanja primata koriste kao temelj gestikularne teorije (Corballis 2009Armstrong i Wilcox 2007;Goldin-Meadow & McNeill 1999). Prvi i osnovni korak u proučavanju jezika u prapovijesti je definiranje samog pojma jezik.…”

“…Kada je riječ o evoluciji jezika, jedna od važnijih tema rasprava vodi se oko pitanja je li pojava ljudskog jezika u svojim samim počecima bila vokalne ili gestikularne prirode (Arbib 2005;Tomasello 2008;Riede et al 2005;Zuberbühler 2005;Hewes 1973). Iako komparativna istraživanja djelomično podržavaju oba stajališta, vokalizacija i govorni jezik imaju nekoliko bitnih prednosti.…”