Stewart, N., & Chater, N. (2002). The effect of category variability in perceptual categorization. Journal of Experimental Psychology: Learning, Memory, and Cognition, 28, 893-907.

Exemplar and distributional accounts of categorization make differing predictions for the classification of a critical exemplar precisely halfway between the nearest exemplars of two categories differing in variability. Under standard conditions of sequential presentation, the critical exemplar was classified into the most similar, least variable category, consistent with an exemplar account. However, if the difference in variability is made more salient, then the same exemplar is classified into the more variable, most likely category, consistent with a distributional account. This suggests that participants may be strategic in their use of either strategy. However, when the relative variability of two categories was manipulated, participants showed changes in the classification of intermediate exemplars that neither approach could account for.