Baronchelli, A.

Loreto, V.

Mukherjee, A.

Puglisi, A.

Tria, F.

City Research Online

Proc. of the Alife XII Conference, Odense, Denmark, 2010 589Aging in the Emergence of Linguistic CategoriesA. Mukherjee1, A. Baronchelli2, V. Loreto1,3, A. Puglisi4,3 and F. Tria11Complex Networks Lagrange Laboratory, ISI Foundation, Torino, Italy2Departament de Fisica i Enginyeria Nuclear, Univ. Politecnica de Catalunya, Barcelona, Spain3Sapienza University of Rome, Physics Department, Rome, Italy4CNR-INFM-SMC, Rome, ItalyExtended AbstractCategories are fundamental to recognize, differentiate and understand the environment. They are meant to provide acoarse-grained description of the world we perceive. For instance, few “basic color terms”, present in natural languages,coarse-grain the infinite number of different colors that humans can possibly perceive. An important question is whethercategories are a manifestation of an underlying structure of nature or an emergent property of the complex interactionsamong individuals themselves as well as with the environment. The current work attempts to seek for an answer to thisquestion by modeling a population of individuals who co-evolve their form-meaning repertoire by playing elementarylanguage games.The Category Game is a computational model designed to investigate how a population of individuals can develop ashared repertoire of linguistic categories, i.e. co-evolve their own system of symbols and meanings, by playing elementarylanguage games (Puglisi et al., 2008). Consensus is reached through the emergence of a hierarchical category structuremade of two distinct levels: a basic layer, responsible for fine discrimination of the environment, and a shared linguisticlayer that groups together perceptions to guarantee communicative success. The only parameter of the model is the JustNoticeable Difference (JND) of the agents defined as the average detectable difference between two stimuli. Remarkably,the number of linguistic categories turns out to be finite and small, as observed in natural languages, even in the limit ofan infinitesimally small JND.The Category Game also allowed to focus on the question of the origins of universal categorization patterns across cultures.In this framework, it has recently been possible to reproduce the outcomes of the World Color Survey (WCS) (Baronchelliet al., 2010). Through the Category Game model, a certain number of non-interacting populations has been simulated,each one developing its own synthetic language. Universal categorization patterns have been discovered among popula-tions whose individuals are endowed with the human JND function, describing the resolution power of the human eye tovariations in the wavelength of the incident light (Long et al., 2006). It turns out that a simple perceptual constraint sharedby all humans, namely the human Just Noticeable Difference (JND), is sufficient to trigger the emergence of universalpatterns that unconstrained cultural interaction fails to produce.A wide open question about the emergence of linguistic categories, and more generally of shared linguistic structures,concerns the role of the timescales. How to reconcile the apparent static character of most of the linguistic structures welearn with the evidences of a fluid character of modern communication systems? Here we report about preliminary studiesthat suggest how the structure of linguistic categories undergoes aging (Henkel et al., 2006): at relatively early stageschanges are very frequent but they become progressively more rare as the system ages; a phenomenon whose intensityincreases with the population size. From this point of view shared linguistic conventions would not emerge as attractorsof a language dynamics, but rather as metastable states.ReferencesBaronchelli, A., Gong, T., Puglisi, A., and Loreto, V. (2010). Modelling the emergence of universality in color naming patterns. PNAS,107:2403–2407.Henkel, M., Pleimling, M., and Sanctuary, R. (2006). Statistical physics of ageing phenomena and the glass transition. Journal of Physics:Conference Series, 40(1).Proc. of the Alife XII Conference, Odense, Denmark, 2010 590Long, F., Yang, Z., and Purves, D. (2006). Spectral statistics in natural scenes predict hue, saturation, and brightness. PNAS, 103(15):6013–6018.Puglisi, A., Baronchelli, A., and Loreto, V. (2008). Cultural route to the emergence of linguistic categories. PNAS, 105:7936.

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