How do categorical sound patterns in language arise and spread?
I have proposed a Similarity-Feedback Model resting on the interaction of two conceptually distinct sources of biases in language production and perception: similarity-biased and externally-biased variation (Wedel 2002, 2006, 2007). Considerable evidence suggests that language production and perception variants are biased toward other similar words and pronunciations, creating a steady tendency for language change to recapitulate and exaggerate existing patterns. Because errors of this type feed back upon themselves to increase similarity over time, they gradually push a system toward categorical behavior even in the absence of any intrinsic or extrinsic bias toward a particular pattern (Wedel 2006, see this simulation). A second source of bias in variation (‘externally-biased variation’) can be idealized as relatively independent of experience, such as the physiological constraints that exist on sound production or perception. Using computational simulations as models of language use
