Exemplar Dynamics Models of the Stability of Phonological Categories
This addresses the problem of how phonological categories remain stable over time for linguists and cognitive scientists, but it is incremental as it builds on existing exemplar theory.
The authors tackled the problem of understanding the stability of phonological categories, such as vowel sounds, by developing a model based on exemplar dynamics. They found that for distinct categories to be preserved, anomalous speech tokens must be discarded rather than stored as exemplars of another category.
We develop a model for the stability and maintenance of phonological categories. Examples of phonological categories are vowel sounds such as "i" and "e". We model such categories as consisting of collections of labeled exemplars that language users store in their memory. Each exemplar is a detailed memory of an instance of the linguistic entity in question. Starting from an exemplar-level model we derive integro-differential equations for the long-term evolution of the density of exemplars in different portions of phonetic space. Using these latter equations we investigate under what conditions two phonological categories merge or not. Our main conclusion is that for the preservation of distinct phonological categories, it is necessary that anomalous speech tokens of a given category are discarded, and not merely stored in memory as an exemplar of another category.