Separating Inhibition and Interference in Retrieval-Induced Forgetting

Abstract

Retrieval-induced forgetting (RIF) is the phenomenon whereby remembering a subset of items impairs memory for related information. There are two main explanations for RIF: the inhibition account, attributing the forgetting to neural suppression, and the competition account, attributing it to associative interference. Prior research has favoured the former, but there are persistent exceptions within the evidence for to each point of differentiation. The first experiment described here tested several confounds identified in prior support for the inhibition account, with a novel adaptation of the Retrieval Practice paradigm. This indicated that these confounds were not issues, but suggested the typical choice of category-exemplar stimuli may allow both processes to act in Retrieval Practice studies. A variation on the Paired-Associates paradigm was used to disentangle these processes across three further experiments, with results indicating that both contribute to RIF. Using unrelated cue-exemplar pairs, we isolated these effects, finding that only the inhibition-attributed effect was dependent on both sleep and the function of the dorsolateral prefrontal cortex. Finally, two further experiments were used to probe the conditions which lead to associations being treated as exclusive, eliciting inhibition in RIF experiments. These revealed that while high-level structural information does not affect the implementation of inhibition, prior evidence of co-occurrence between exemplars can attenuate the RIF effect. Overall, the present work indicates that RIF is predominantly driven by inhibition, but the contribution of competition should not be overlooked, as it is not possible to account for all demonstrations of the phenomenon with inhibition alone. When these effects need to be separated, the novel Paired-Associates paradigm is a useful alternative to the traditional Retrieval Practice paradigm, allowing for the independent manipulation of both processes.