How Minds Made Language (4): Communication and Behavioural Control

This post explores communication and behavioural control as a precursor to language's evolution. We will dive into how primates' call variants demonstrate the evolutionary intermediary between syntactical and non-syntactical vocalisations. Additionally, we will also cover how the development of voluntary control over performing calls and one's vocal tract is essential for developing language communication abilities.

Call Variants

Language users employ syntax to enable listeners to better understand by discerning relationships between words.[i] Language is formed from complex sequences of meaningless and meaningful units (phonological & lexical syntax); an intermediary evolutionary stage between non-syntactical and syntactical language is found in non-human primates.[ii] Chimpanzees and bonobos recombine and break down calls to form alternative meanings. These long (compound) calls are formed from small segments of distinguishable units which hold ‘traditional’ call functions (e.g., alarm calls), and are combined in different patterns (lexical syntax); chimpanzees also insert uniquely located acoustic features into their calls (phonological syntax).

These call variations distinguish the vocalisations of group members; such member recognition becomes more important with increasingly complex social structures.[ii] Arguably, these complex social groups selected for phonological syntax; the subhuman level of phonological syntax presented above does not enable freely combinable call-variants, although it remains a precursor for the evolution of phonemes. Phonological syntax (phoneme recombination) enables language to have a larger repertoire of vocabulary.[iii] Alternatively, primate lexical syntax does exhibit free combination, but it is limited to the few ‘traditional calls’.[ii] Sexual selection for better communicators caused lexical syntax to evolve, reducing ambiguities in rapidly spoken complex utterances.[iv] Despite some syntactical abilities, primate species cannot form sequences of calls into sentences but present an intermediary evolutionary stage important for sentence understanding, member recognition and phoneme production.[vi]

Voluntary control

Voluntary control over the vocal tract is essential for language; with the increasing importance of vocalisations, increased vocal control is selected for.[iii] Mostly automatic vocalisations are made by primates, whilst humans exhibit some voluntary control.[v] However, research has demonstrated cases of voluntary control in primates. Cheney & Seyfarth describe a case in vervet monkeys where alarm calls for predators are more likely to be conducted in the presence of kin.[iii] Unlike other primates, humans have complete control over their vocal tract, apart from gesture-calls such as smiling, laughing, and gasping, which can be involuntary; we can assume that an equivalent amount of voluntary control over human gesture-calls is present in vervet alarm calls.

Moreover, copulation calls in some species of primates can be suppressed when females are mating with lower-ranking males. [viii] Distinct protosyllables needed for the evolution of language required modulation of their acoustic properties.[vii] Another study found that changes in jaw and lip configuration in rhesus monkeys caused modulation in their calls. Such modulations are a step towards syntactic properties (see call variants) and thus, language, requiring increased voluntary control. Furthermore, an increasing vocabulary repertoire selects for vocal control to enable the efficient use of a larger quantity of sounds to distinguish words.[iii]

[i] Vigliocco, G. (2000). Language processing: The anatomy of meaning and syntax. Current Biology, 10(2), R78-R80. doi:10.1016/s0960-9822(00)00282-7

[ii] Ujhelyi, M. (1998). Long-call structure in apes as a possible precursor for language. In J. R. Hurford, M. Studdert-Kennedy, C. Knight (Eds.), Approaches to the evolution of language: Social and Cognitive Bases (pp. 177-187). Cambridge, New York: Cambridge Univ. Press.

[iii] Burling, R. (2005). The talking ape: How language evolved. Oxford: Oxford University Press.

[iv] Bickerton, D. (1998). Catastrophic Evolution. In J. R. Hurford, M. Studdert-Kennedy, C. Knight (Eds.),  Approaches to the evolution of language: Social and Cognitive Bases (pp. 350-353). Cambridge: Cambridge Univ. Press. 

[v] Aitchison, J. (1998). On discontinuing the continuity-discontinuity debate. In J. R. Hurford, M. Studdert-Kennedy, C. Knight (Eds.), Approaches to the evolution of language: Social and Cognitive Bases (pp. 20-22). Cambridge, New York: Cambridge Univ. Press.

[vi] Ulbaek, I. (1998). The origin of language and cognition. In J. R. Hurford, M. Studdert-Kennedy, C. Knight (Eds.), Approaches to the evolution of language: Social and Cognitive Bases (pp. 30-36). Cambridge, New York: Cambridge Univ. Press.

[vii] Studdert-Kennedy, M. (1998). The particulate origins of language generativity. In J. R. Hurford, M. Studdert-Kennedy, C. Knight (Eds.), Approaches to the evolution of language: Social and Cognitive Bases (pp. 208-209). Cambridge, New York: Cambridge Univ. Press.

[viii] Byrne, Whiten, (1992). In J. R. Hurford, M. Studdert-Kennedy, C. Knight (Eds.), Approaches to the evolution of language: Social and Cognitive Bases (pp. 20-22). Cambridge, New York: Cambridge Univ. Press.