Simulation of Explicit and Implicit Category Learning: Evidence for a Single Learning System

Previous experiments (Waldron & Ashby, 2001) showed that category learning was differentially impaired by a concurrent Stroop task, depending on the type of rule used to categorize items. Learning was more impaired for simple explicit rules than for complex implicit rules. The present simulation suggests that the multiple learning systems hypothesized by Waldron and Ashby are not necessary to explain their results because a single learning system provides a parsimonious account of the data. In this model, the harder of two concurrent tasks determines learning time. Therefore, combined task complexity explains why the concurrent Stroop task impairs learning in the explicit group more than in