Chater, N., Vitányi, P. M. B., & Stewart, N. (2001). Universal generalization and universal inter-item confusability. Behavioral and Brain Sciences, 24, 659-660.

We argue that confusability between items should be distinguished from generalization between items. Shepard's data concern confusability, but the theories proposed by Shepard and Tenenbaum & Griffiths concern generalization, indicating a gap between theory and data. We consider the empirical and theoretical work involved in bridging this gap.