Popov, V., Marevic, I., Rummel, J., & Reder, L. M. (2019).
Psychological Science, 30(9), 1303–1317.
https://doi.org/10.1177/0956797619859531
Abstract
We used an item-method directed forgetting paradigm to test whether instructions to forget or to remember one item in a list affects memory for the subsequent item in that list. In two experiments, we found that free and cued recall were higher when a word-pair was preceded during study by a to-be-forgotten (TBF) word pair. This effect was cumulative – performance was higher when more of the preceding items during study were TBF. It also interacted with lag between study items – the effect decreased as the lag between the current and a prior item increased. Experiment 2 used a dual-task paradigm in which we suppressed either verbal rehearsal or attentional refreshing during encoding. We found that neither task removed the effect, thus the advantage from previous TBF items could not be due to rehearsal or attentional borrowing. We propose that storing items in long-term memory depletes a limited pool of resources that recovers over time, and that TBF items deplete fewer resources, leaving more available for storing subsequent items. A computational model implementing the theory provided excellent fits to the data.
General Discussion
We demonstrated a previously unknown DF (Directed Forgetting) after-effect of remember and forget instructions in an item method DF paradigm on memory for the items that follow a pair that was to be remembered versus forgotten: cued and free recall for word pairs was higher when people were instructed to forget the preceding word pair. This effect was cumulative, such that performance was even better when more of the preceding pairs had to be forgotten. The size of the DF after-effect depended on how many pairs ago the DF instruction appeared during study. Specifically, the immediately preceding word-pair provided a stronger DF aftereffect than when the DF instruction appeared several word-pairs ago. Finally, neither increased rehearsal nor attentional borrowing of TBR items could explain why memory for the subsequent item was worse in those cases – the DF after-effects remained stable, even when rehearsal was suppressed or attention divided in a dual-task paradigm.
The DF after-effects are replicable and are remarkably consistent across the two experiments – the odds
ratio associated with items preceded by TBR items rather than TBF items at lag one was 0.66 in the prior
study and 0.67 in the new experiment. Similarly, the odds ratio for the effect of cues at lag two were 0.77
and 0.76 in the two studies. Thus, this represents a robust and replicable phenomenon. Additionally, the
multinomial storage–retrieval model confirmed that DF after-effects are clearly a storage phenomenon.
Summary: forgetting is not always a bad thing. In fact, it can sometimes be helpful. For example, if we are trying to learn a new skill, it may be helpful to forget some of the old information that is no longer relevant. This will free up working memory resources, which can then be used to store the new information. It may be helpful to include instructions to forget some information in learning materials. This will help to ensure that the learners are able to focus on the most important information.
