The authors tested 288 participants in the classic category-learning tasks introduced by Shepard, Hovland, and Jenkins (1961). However, separable-dimension stimuli were used in previous tests, whereas integral-dimension stimuli were used in the present study. In contrast to previous results, which showed a superiority for Problem Type II over Problem Types III, IV, and V, the reverse pattern was observed in the present research. This result confirms a fundamental prediction made by modern exemplar-based models of classification learning. The results are interpreted in terms of the extent to which selective-attention learning mechanisms operate when separable-dimension versus integral-dimension stimuli are used.