The roles of delay and retroactive interference in retrieval-induced forgetting

When subjects study items from different categories and then repeatedly retrieve some of the items from some of the categories, retrieval practice typically improves recall of the practiced items but impairs recall of related but unpracticed items, relative to control items from unpracticed categories. Here, we report the results of three experiments, in which we examined practiced and unpracticed items' delay-induced forgetting (Exp. 1) and their susceptibility to retroactive interference (Exps. 2 and 3). Control items showed the expected memory impairment after longer delay between practice and test and in the presence of retroactive interference. In contrast, both the practiced and the related unpracticed items showed hardly any forgetting under these conditions. The findings are consistent with the results from recent testing-effect studies, which have reported reduced delay-induced forgetting and reduced susceptibility to interference for retrieval-practiced items, and generalize the results to related unpracticed items. The findings are discussed with respect to the inhibitory and noninhibitory accounts of retrieval-induced forgetting, as well as the possible role of selective segregation processes, which may be induced by retrieval practice.