Abstract
The neurocognitive basis of memory retrieval is often examined by investigating brain potential old/new effects, which are differences in brain activity between successfully remembered repeated stimuli and correctly rejected new stimuli in a recognition test. In this study, we combined analyses of old/new effects for words with an item-method directed-forgetting manipulation in order to isolate differences between the retrieval processes elicited by words that participants were initially instructed to commit to memory and those that participants were initially instructed to forget. We compared old/new effects elicited by to-be-forgotten (TBF) words with those elicited by to-be-remembered (TBR) words in both an explicit-memory test (a recognition test) and an implicit-memory test (a lexical-decision test). Behavioral results showed clear directed forgetting effects in the recognition test, but not in the lexical decision test. Mirroring the behavioral findings, analyses of brain potentials showed evidence of directed forgetting only in the recognition test. In this test, potentials from 450–650 ms (P600 old/new effects) were more positive for TBR relative to TBF words. By contrast, P600 effects evident during the lexical-decision test did not differ in magnitude between TBR and TBF items. When taken in the context of prior studies that have linked similar parietal old/new effects to the recollection of episodic information, these data suggest that directed-forgetting effects manifest primarily in greater episodic retrieval by TBR than TBF items, and that retrieval intention may be important for these directed-forgetting effects to occur.
Highlights
A great deal of research interest has been focused on directed forgetting (DF), or the process of intentionally forgetting information that has been learned
To assess the effects of the directed forgetting cues on participants’ recognition accuracy, statistical analyses focused on the percentage of ‘‘old’’ responses registered for each stimulus category on the explicit memory test
Significantly more hits were registered for TBR relative to TBF words [t(13) = 3.68, p,0.01], indicating that the directed forgetting manipulation affected performance on the explicit memory test
Summary
A great deal of research interest has been focused on directed forgetting (DF), or the process of intentionally forgetting information that has been learned. When participants’ memory is tested later, it is typically found that stimuli that were initially marked as to-be-remembered (TBR) are recognized or recalled with greater accuracy relative to items that were marked as to-beforgotten (TBF) These findings have been obtained when TBR and TBF cues are intermixed within the same study list (referred to as item method directed forgetting), as well as when entire study lists are presented and subsequently designated as TBR or TBF (referred to as list method directed forgetting). It has been argued that the involuntary retrieval of both negative and non-negative information from memory is a pervasive but understudied aspect of human experience (for reviews, see [4,5]) For these reasons, it is important to investigate the potential for DF instructions to affect incidental as well as intentional expressions of memory
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