Category Discontinuity Interacts with Verbal Rule Complexity 1 Within-Category Discontinuity Interacts with Verbal Rule Complexity in Perceptual Category Learning

Two experiments were conducted that provide a test of the predicted interaction between within-category discontinuity and verbal rule complexity on the efficiency of the neurobiologically-motivated procedural-based and hypothesis-testing category learning systems, and by extension, on information-integration and rule-based category learning. In Experiment 1, within-category discontinuity adversely affected information-integration category learning but not rule-based category learning. Model based analyses of the information-integration data suggested that some participants improved performance by recruiting more “units” in the discontinuous condition. Even so, participants in the discontinuous condition evidenced more sub-optimal unit placement, less deterministic responding or both. In Experiment 2, verbal rule complexity adversely affected rule-based category learning but not information-integration category learning. Model-based analyses of the rule-based data suggested that the effect was on both decision criterion learning and the variability associated with the memory for, and trial-by-trial application of, the decision criteria. Transfer performance suggested that the hypothesis-testing system learns an abstract rule and can generalize to parts of the stimulus space that were not trained, whereas the procedural-based learning system learns to assign categorization responses to regions of perceptual space and does not generalize well to untrained parts of the stimulus space. These results suggest that within-category discontinuity and decision rule complexity differentially impact information-integration and rule-based category learning, and provide information regarding the detailed processing characteristics of these two proposed category learning systems.