Withdrawal of spatial overt attention following intentional forgetting: evidence from eye movements

Let me give you something to think about: Does needing to remember something new make it easier to forget something old?

In an item-method directed forgetting task, memory instructions presumably operate by promoting further rehearsal of to-be-remembered (TBR) items and limiting encoding of to-be-forgotten (TBF) items. We asked whether diverting attentional resources away from TBF items and towards a new item that needed to be committed to memory would improve forgetting. To this end, study words in our experiments were presented singly followed by a remember instruction (single-TBR), by a forget instruction (single-TBF), or else were replaced by a new word to be remembered (replace-TBR) in place of the original study word which could be forgotten (replace-TBF). A typical directed forgetting effect was observed across single and replace trials. However, there was no compelling evidence that forgetting was better for replace-TBF compared to single-TBF words, suggesting that, by itself, the explicit redirection of attentional and other processing resources away from forget items may not be sufficient to improve item-method directed forgetting.

Instructions to shift eyes do not increase item-method directed forgetting

Successful forgetting of recently-studied information has been shown to be positively correlated with eye movements [Lee, Y. (2018). Withdrawal of spatial overt attention following intentional forgetting: Evidence from eye movements. Memory (Hove, England), 26(4), 503-513. https://doi.org/10.1080/09658211.2017.1378360]. We tested whether eye movements caused forgetting by manipulating instructions to move eyes following forget and remember cues in item-method directed forgetting. In Experiment 1, participants were instructed to move eyes to the periphery after TBF trials or to focus on the centre where the TBF word and cue had been presented. In Experiment 2, we manipulated eye movement instructions within participants such that on half of the TBR and TBF trials participants shifted their eyes to the periphery, and on the other half of the trials, participants focused on the centre of the screen. Experiment 3 replicated Experiment 2 with an added probe task which ensured participants were moving their eyes as instructed. Results overall showed eye movements did not increase directed forgetting. Instructing participants to shift or focus eyes did not interact with the effectiveness of directed forgetting. Furthermore, metacognitive measures collected during study indicated that participants are sensitive to the significant effects of directed forgetting, but - like recall - judgments were not affected by eye movement instructions. From these findings, we concluded that eye movements do not promote intentional forgetting.

Oscillatory Correlates of Intentional Forgetting: The Role of Theta and Alpha Power in Item-Method Directed Forgetting

Results from item-method directed forgetting suggest that individuals are able to intentionally forget processed information. Most research suggests that either selective rehearsal of to-be-remembered or inhibitory control of to-be-forgotten information is accountable for the effects of intentional forgetting. Some research, however, hypothesized that the time to process information mediates the underlying mechanism. To test this hypothesis, the current study investigated associations between oscillatory power in theta (3–7.5 Hz) and alpha frequencies (8–13 Hz) and intentional forgetting in human participants and explored whether or not these mechanisms depended on processing time. Previously, theta power was shown to be associated with the creation of episodic memory traces and alpha power with inhibition. We therefore expected to find associations between these neural signatures and behavioral effects. Consistent with our hypotheses, we revealed increased theta power for to-be-remembered and increased alpha power for to-be-forgotten information and that the effects of activity in both frequency bands were influenced by the time individuals were given for processing the memory cue. These results suggest that not one but two mechanisms, rehearsal and inhibitory control, are accountable for item-method directed forgetting, both with different temporal profiles.

Intention matters more than attention: Item-method directed forgetting of items at attended and unattended locations

This study embedded attentional cues in the study phase of an item-method directed forgetting task. We used an unpredictive onset cue (Experiment 1), a predictive onset cue (Experiment 2), or a predictive central cue (Experiments 3-6) to direct attention to the left or right. In Experiments 1-5, this was followed by a pink or blue study word that required a speeded colour discrimination; in Experiment 6, it was followed by a pink or blue word or nonword that required a lexical decision. Each study word was followed by an instruction to Remember or Forget. A yes-no recognition test confirmed better recognition of to-be-remembered words than to-be-forgotten words; a cueing effect confirmed the effectiveness of predictive cues in allocating attentional resources. There was, however, no evidence that the directed forgetting effect differed for attended and unattended words: Encoding depends more on the memory intention formed after a study word has disappeared than on the availability of processing resources when that word first appears.

Emotional memories are (usually) harder to forget: A meta-analysis of the item-method directed forgetting literature

The current meta-analysis explored whether emotional memories are less susceptible to item-method directed forgetting than neutral memories. Basic analyses revealed superior memory for remember (R) than forget (F) items in both the neutral, M = 19.6%, CI_95% [16.1, 23.1], and the emotional, M = 15.1%, CI_95% [12.4, 17.7], conditions. Directed forgetting in either valence condition was larger for (a) words than for other stimuli; (b) recall than recognition tests; (c) studies that used recall prior to recognition testing; (d) shorter lists; and (e) studies that included buffer items. Direct comparison of the magnitude of the directed forgetting effect across neutral and emotional conditions within studies revealed relatively diminished directed forgetting of emotional items compared to neutral items, with an average difference of 4.2%, CI_95% [2.0, 6.4]. However, the nature of this finding varied broadly across studies, meaning that whether - and to what degree - emotional memories are more resilient than neutral memories likely depends on the methodological features of the study in question. Moderator analyses revealed larger differences (a) in studies for which the emotional items were more arousing than the neutral items, and (b) when buffer items were included. Together, these findings suggest that emotional memories are often more resilient to intentional forgetting than neutral memories, although further research is necessary to characterize the circumstances under which these differences emerge.

Forgetting under difficult conditions: Item-method directed forgetting under perceptual processing constraints

Intentional forgetting of unwanted items is effortful, yet directed forgetting seems to improve when a secondary task is performed. According to the cognitive load hypothesis of directed forgetting, allocating attentional resources to another task improves forgetting by restricting unwanted encoding of to-be-forgotten (TBF) items. Alternatively, it might be that anything that makes studying more difficult will encourage greater effort to perform the task well and therefore lead to improved intentional forgetting. To assess these proposals we imposed data-processing limitations on study words in an item-method directed forgetting paradigm. Across six experiments, the perceptual quality of study words was manipulated by varying: (1) the duration of study word presentation (Experiments 1-4); (2) the contrast of the displayed word against its visual background (Experiment 5); or (3) the amount of visual background noise on which the word was presented (Experiment 6). In Experiments 4-6, a lexical decision task corroborated the difficulty of study word processing. Despite evidence that relatively low visual contrast and relatively high visual background noise, in particular, create challenging conditions, we found no evidence that perceptual quality impacts the magnitude of the directed forgetting effect. This work suggests that data limitations have no discernible effect on forgetting and corroborate that only attentional resource limitations improve directed forgetting.

Remember to blink: Reduced attentional blink following instructions to forget

This study used rapid serial visual presentation (RSVP) to determine whether, in an item-method directed forgetting task, study word processing ends earlier for forget words than for remember words. The critical manipulation required participants to monitor an RSVP stream of black nonsense strings in which a single blue word was embedded. The next item to follow the word was a string of red fs that instructed the participant to forget the word or green rs that instructed the participant to remember the word. After the memory instruction, a probe string of black xs or os appeared at postinstruction positions 1-8. Accuracy in reporting the identity of the probe string revealed an attenuated attentional blink following instructions to forget. A yes-no recognition task that followed the study trials confirmed a directed forgetting effect, with better recognition of remember words than forget words. Considered in the context of control conditions that required participants to commit either all or none of the study words to memory, the pattern of probe identification accuracy following the directed forgetting task argues that an intention to forget releases limited-capacity attentional resources sooner than an instruction to remember-despite participants needing to maintain an ongoing rehearsal set in both cases.