Self-organization and categorical behavior in phonology

Generative models of phonology account for output patterns through a complex grammar applied over a minimal lexicon. In contrast, many natural complex patterns result from the gradual accumulation of structure through repeated local interactions. In this dissertation I present results of simulations supporting the proposal that some phonological patterns can be accounted for through self-organization within an analogically structured lexicon, in response to forcing from external biases. In Chapter 1, I show that patterns accounted for by the Optimality-Theoretic principles of constraint dominance and strict constraint dominance can be shown to spontaneously arise in analogically-structured systems, driven by competition between leveling pressures within the lexicon and differentiating pressures from lexiconexternal performance biases.; Phonological systems exhibit 'constrained contrast' in two distinct ways: first, phonologies exhibit only a subset of cross-linguistically attested contrasts, formed from a subset of possible features in combination. Second, crosslinguistically infrequent elements also tend to occur less frequently in a language that does have them. In Chapter 2, I present evidence that both of these patterns can be accounted for diachronically through indirect selection over phonetic variants, given the assumptions that, (1) lexical categories are richly specified, (2) a perceived utterance updates the content of a lexical category only if it is identified as an example of that lexical category, and (3) lexical categories can influence each others' production in proportion to phonological similarity.; When a simulated speaker/hearer pair alternately communicate their lexicons to each other under these conditions their lexicons converge. Further, when an output is too close to multiple categories, it is less likely be consistently categorized, with the result that it has less influence on the evolution of the pairs' lexicons, resulting in pressure on lexical categories to remain contrastive. When biases against certain features or feature combinations are introduced, the pairs' lexicons evolve to avoid as many of these 'less-fit' elements as possible. However, when avoidance of all marked elements would result in insufficient contrast, the lexicons evolve to utilize a subset of less-fit elements, but at a lower frequency than fitter elements.