Self-Organization and Morphogenesis
in the Evolution of Human Speech Sounds
Human vocalization systems are characterized by complex structural properties. They are combinatorial, based on the systematic reuse of phonemes, and the set of repertoires in human languages is characterized by both strong statistical regularities – universals—and a great diversity. Besides, they are conventional codes culturally shared in each community of speakers. What is the origins of the forms of speech? What are the mechanisms that permitted their evolution in the course of phylogenesis and cultural evolution? How can a shared speech code be formed in a community of individuals?
I have been studying the way the concept of self-organization, and its interaction with natural selection, can throw light on these three questions. The hypothesis I am studying is that the origins of speech can be understood only as the result of complex self-organized dynamical interactions between speaking and listening individuals, each of them being a complex system in which the vocal tract, the ear, and the neural system that connects them are coupled. The dynamics of complex systems is difficult to understand, and one of the best tools to study them is computer modeling. This is why I have developped a series of computational models, which allowed to show that a basic neural equipment for adaptive holistic vocal imitation, coupling directly motor and perceptual representations in the brain, can generate spontaneously shared combinatorial systems of vocalizations in a society of babbling individuals. Furthermore, this has allowed to show how morphological and physiological innate constraints (i.e. properties of the body) can interact with these self-organized mechanisms to account for both the formation of statistical regularities and diversity in vocalization systems.
Keywords: self-organization, natural selection, evolution of speech, combinatoriality, computational model.
I wrote a book the following book about this research:
Oudeyer, P-Y. (2006) Self-Organization in the Evolution of Speech, Studies in the Evolution of Language, Oxford University Press. Bibtex (Translated by James R. Hurford.)
The following book chapter synthesizes the main ideas in this book:
Oudeyer, P-Y. (2013) Self-Organization and
Complex Dynamical Systems in the Evolution of Speech, in Smith, K. and
Binder, P. eds., The Language Phenomenon, Springer. Bibtex
My main papers on this subject:
1) The three following papers summarize the main results of a recent model in which ears and vocal tracts are coupled with simple neural maps. The first one shows how the coupling of babbling agents produces a shared system of syllable system at the population level, and how discreteness in syllable systems can appear:
Oudeyer, P-Y. (2005) The Self-Organization of Speech Sounds, Journal of Theoretical Biology, Volume 233, Issue 3, pp.435--449. pdf or html. The authoritative version of this article can be accessed via Science Direct
The second paper describes how combinatoriality, i.e. phonemic coding, and basic rules of phonotactics can form:
Oudeyer, P-Y. (2005) The self-organisation of combinatoriality and phonotactics in vocalization systems, Connection Science, vol. 17, No. 3, pp. 1-17.
The third one provides an evolutionary interpretation of the computational models developed in the two previous papers, basically arguing that evolutionary step from analogic and basic vocal imitation to shared combinatorial speech codes might have been rather small:
Oudeyer, P-Y. (2007) From vocal replication to shared combinatorial speech codes: a small step for evolution, a big step for language, In Lyon, C., Nehaniv L. and A. Cangelosi, editor, Emergence of Communication and Language, pp. 207--222, Lecture Notes in Computer Science, Springer-Verlag. Berlin. bibtex reference
2) Another model which I developed showed how syllable systems constructed through cultural evolution could become adapted to the cognitive constraints of speakers and listeners: syllable systems were culturally selected for learnability. This work was based on an extensions of Bart de Boer's work on vowel systems to syllable systems.
Oudeyer, P-Y (2005) How phonological structures can be culturally selected for learnability, Adaptive Behavior, 13(4), pp. 269--280. bibtex reference
A related and more general paper:
Oudeyer P-Y., Kaplan F. (2007) Language Evolution as a Darwinian Process: Computational Studies, Cognitive Processing, , 8(1), pp. 21--35. DOI: 10.1007/s10339-006-0158-3.
3) In french:
Oudeyer, P-Y. (2009) L'auto-organisation dans l'évolution de la parole, in Dehaene, S., and Petit, C., Parole et Musique: Aux origines du dialogue humain, Colloque annuel du Collège de France, pp. 83-112, Odile Jacob.