page_title: Origin of speech
section_title: Self-organization theory
hierarchical_section_title: Origin of speech / Origin of speech sounds / Self-organization theory
caption_attribution_description: Dansk: Billede af "sort sol" ved Ørnsø i SilkeborgEnglish: Blick of "sort sol"
context_page_description: The origin of speech refers to the more general problem of the origin of language in the context of the physiological development of the human speech organs such as the tongue, lips and vocal organs used to produce phonological units in all human languages.
context_section_description: Self-organization  characterizes systems where macroscopic structures are spontaneously formed out of local interactions between the many components of the system. In self-organized systems, global organizational properties are not to be found at the local level. In colloquial terms, self-organization is roughly captured by the idea of "bottom-up" (as opposed to "top-down") organization. Examples of self-organized systems range from ice crystals to galaxy spirals in the inorganic world, and from spots on the leopard skins to the architecture of termite nests or shape of a flock of starlings.
  According to many phoneticians, the sounds of language arrange and re-arrange themselves through self-organization Speech sounds have both perceptual ("how you hear them") and articulatory ("how you produce them") properties, all with continuous values. Speakers tend to minimize effort, favoring ease of articulation over clarity. Listeners do the opposite, favoring sounds that are easy to distinguish even if difficult to pronounce. Since speakers and listeners are constantly switching roles, the syllable systems actually found in the world's languages turn out to be a compromise between acoustic distinctiveness on the one hand, and articulatory ease on the other.
  How, precisely, do systems of vowels, consonants and syllables arise? Agent-based computer models take the perspective of self-organisation at the level of the speech community or population. The two main paradigms here are (1) the iterated learning model and (2) the language game model. Iterated learning focuses on transmission from generation to generation, typically with just one agent in each generation.
  In the language game model, a whole population of agents simultaneously produce, perceive and learn language, inventing novel forms when the need arises.
  Several models have shown how relatively simple peer-to-peer vocal interactions, such as imitation, can spontaneously self-organize a system of sounds shared by the whole population, and different in different populations. For example, models elaborated by Berrah et al., as well as de Boer, and recently reformulated using Bayesian theory, showed how a group of individuals playing imitation games can self-organize repertoires of vowel sounds which share substantial properties with human vowel systems. For example, in de Boer's model, initially vowels are generated randomly, but agents learn from each other as they interact repeatedly over time. Agent A chooses a vowel from her repertoire and produces it, inevitably with some noise. Agent B hears this vowel and chooses the closest equivalent from her own repertoire. To check whether this truly matches the original, B produces the vowel she thinks she has heard, whereupon A refers once again to her own repertoire to find the closest equivalent. If this matches the one she initially selected, the game is successful, otherwise, it has failed. "Through repeated interactions," according to de Boer, "vowel systems emerge that are very much like the ones found in human languages."
  In a different model, the phonetician Björn Lindblom was able to predict, on self-organizational grounds, the favored choices of vowel systems ranging from three to nine vowels on the basis of a principle of optimal perceptual differentiation.
  Further models studied the role of self-organization in the origins of phonemic coding and combinatoriality, which is the existence of phonemes and their systematic reuse to build structured syllables. Pierre-Yves Oudeyer developed models which showed that 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, including phonotactic patterns, in a society of babbling individuals. These models also characterized how morphological and physiological innate constraints can interact with these self-organized mechanisms to account for both the formation of statistical regularities and diversity in vocalization systems.
caption: Birds flocking, an example of self-organization in biology
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