A large body of literature agrees that accessing a target memory appears to trigger a difference-of-Gaussian memory activation pulse under which the target representation is activated and categorically flanking items are suppressed and forgotten. The nature of the underlying forgetting mechanism is far from settled, with support for several theories of forgetting. Here we argue the debate is partly fueled by different forgetting mechanisms underlying the forgetting of different memoranda. We capitalized on the unique aspect of the recognition-induced forgetting paradigm to test forgetting of both pictures and words in identical recognition-practice and restudy tasks. We found that memory for pictures and words followed different patterns of forgetting. Specifically, forgetting was retrieval specific for words, in that forgetting occurred only when words were recognized, and not when words were merely restudied. However, forgetting was not retrieval specific for pictures, in that forgetting occurred both when pictures were recognized as well as restudied. Further, patterns of forgetting operated along different category-level groupings for pictures and words. Words grouped along the superordinate level were susceptible to forgetting but pictures were not. The strength of this design is the ability to directly compare forgetting for different memoranda, establishing that patterns of forgetting are modality specific. These findings demonstrate that the mechanisms underlying forgetting may differ as a function of the particular memoranda, emphasizing the need for examining forgetting in long-term memory across modalities.

Human alpha-band activity (8–12 Hz) has been proposed to index a variety of mechanisms during visual processing. Here, we distinguished between an account in which alpha suppression indexes selective attention versus an account in which it indexes subsequent working memory storage. We manipulated two aspects of the visual stimuli that perceptual attention is believed to mitigate before working memory storage: the potential interference from distractors and the size of the focus of attention. We found that the magnitude of alpha-band suppression tracked both of these aspects of the visual arrays. Thus, alpha-band activity after stimulus onset is clearly related to how the visual system deploys perceptual attention and appears to be distinct from mechanisms that store target representations in working memory.

Intentional forgetting refers to the attempt to marshal top-down control to purposefully forget, and has been demonstrated in the laboratory using directed forgetting paradigms. Here, we asked whether the mechanisms of top-down control can run in the opposite direction to prevent the forgetting of information; that is, can we actively resist unintentional forgetting? Recognition-induced forgetting is an unintentional forgetting effect in which accessing one memory leads to the forgetting of related memories. Just as intentional forgetting possesses intuitively appealing control over eliminating undesirable memories, resisting unintentional forgetting over desired memories would improve cognitive performance. We showed subjects a 9-min video to teach them about the recognition-induced forgetting paradigm and how recognition of certain objects unintentionally leads to forgetting of semantically related objects. After testing their comprehension of the video, we conducted a typical recognition-induced forgetting experiment and challenged the subjects to resist this form of unintentional forgetting. Despite their knowledge of the forgetting effect, and the challenge to subjects to resist the forgetting induced by the paradigm, recognition-induced forgetting persisted. These results show that knowledge of this unintentional forgetting phenomenon and the challenge to resist forgetting do not eliminate it, suggesting that it is cognitively impenetrable. Electronic supplementary material The online version of this article (10.1186/s41235-019-0180-5) contains supplementary material, which is available to authorized users.

Induced forgetting occurs when accessing an item in memory appears to harm memory representations of categorically related items. However, it is possible that the actual memory representations are unharmed. Instead, people may just change how they make decisions. Specifically, signal detection theory suggests this apparent forgetting may be due to participants shifting their decision criterion. Here, we used behavioral and electrophysiological measures to determine whether induced forgetting is truly due to changes in how items are represented or simply due to a shifting criterion. Participants' behavior and brain activity showed that induced forgetting was due to changes in the strength of the underlying representations, weighing against a criterion shift explanation of induced forgetting.

Here we employ a novel analysis to address the question: what causes induced forgetting of pictures? We use baseline memorability as a measure of initial memory strength to ask whether induced forgetting is due to (1) recognition practice damaging the association between the memory representation and the category cue used to activate the representation, (2) the updating of a memory trace by incorporating information about a memory probe presented during recognition practice to the stored trace, (3) inhibitory mechanisms used to resolve the conflict created when correctly selecting the practiced item activates competing exemplars, (4) a global matching model in which repeating some items will hurt memory for other items, or (5) falling into the zone of destruction, where a moderate amount of activation leads to the highest degree of forgetting. None of the accounts of forgetting tested here can comprehensively account for both the novel analyses reported here and previous data using the induced forgetting paradigm. We discuss aspects of forgetting theories that are consistent with the novel analyses and existing data, a potential solution for existing models, proposals for future directions, and considerations when incorporating memorability into models of memory.