Figure 10.

Illustration of exemplar-based and usage-based models to account for the effects of diversity in input on production of vowels. The exemplar-based model assumes that every perceived variant of a word (the boxes labeled “a” through “e”) gives rise to an exemplar in a direct acoustic-to-lexical mapping. Frequency of occurrence is represented by the size of the box for the exemplar. The usage-based model assumes that linguistic units are gradient categories formed in continuous fashion from experienced tokens. For both models, spoken words are produced in variable fashion reflecting the input diversity.