The effect of deferring feedback on rule-based and information-integration category learning.
Previous work has shown that deferring feedback significantly impairs two-dimensional information-integration category learning, often thought to recruit an implicit learning system, but leaves intact unidimensional rule-based learning, commonly assumed to engage an explicit system (Smith et al., 2014). These results were taken to support the influential COmpetition between Verbal and Implicit Systems (COVIS) dual-process theory. This conclusion has subsequently been challenged by the finding that this dissociation disappears when the number of relevant dimensions is matched between tasks (Le Pelley et al., 2019). However, as well as replacing a unidimensional rule-based task with a two-dimensional conjunction task, Le Pelley et al. also changed the stimuli that were used in their study making it unclear which of these alterations was driving the difference in results. The current paper directly examined how both category structure and stimulus type influence the deferred feedback effect. We replicated both the original sets of results but found that deferred feedback also impaired information-integration learning to a greater extent than a conjunction task when Smith et al.s original stimuli were used. This result suggests that the effect of deferred feedback on category learning is more complicated than has previously been documented and highlights the critical role the choice of stimuli has in determining whether the effect is obtained.