Forming a new prospective memory intention can reduce prospective memory commission errors

Prospective memory (PM) refers to remembering to perform intended actions in the future. While much research focuses on PM omission errors (forgetting to perform the intended action), recent studies highlight PM commission errors – repeatedly performing an action that is no longer relevant. Commission errors can have serious consequences, particularly for older adults. This study focuses on commission errors resulting from completed PM intentions that remain active. Existing event-based PM paradigms typically involve an active phase (performing both an ongoing task and the PM task) and a finished phase (performing only the ongoing task, with the PM cue reappearing). However, real-life PM involves multiple, sequentially formed intentions. This study investigated the impact of forming a new PM intention in the finished phase on commission errors related to the completed intention. Two primary theoretical perspectives are considered: the attentional dependence hypothesis (where a new intention shifts attention, potentially increasing commission errors) and the intention overwriting hypothesis (where a new intention overwrites the representation of the completed intention, reducing commission errors). Previous research on this topic yielded mixed results, with some studies supporting attentional dependence and others supporting intention overwriting, possibly due to differences in the similarity of old and new PM cues.

Several studies have explored the impact of new PM intentions on commission errors. Walser et al. (2012, 2017) utilized repeated PM cue paradigms, finding that similar new PM cues increased commission errors, consistent with the attentional dependence hypothesis. However, Anderson and Einstein (2017) found no such effect, potentially due to using semantically dissimilar cues. Implementation intentions, a strategy involving "if-then" planning, have been shown to improve PM performance but may also increase commission errors in the active phase. This study examined whether implementing a new intention with an implementation intention strategy in the finished phase would affect commission errors differently than simply performing a new PM task.

Eighty-six participants were randomly assigned to one of three groups: a non-new PM group (only ongoing task in phase 2), a new PM group (new PM task added in phase 2), and an implementation intention group (new PM task with "if-then" encoding in phase 2). The ongoing task was a 1-back letter recognition task. In phase 1 (active phase), participants performed the ongoing task and a PM task (identifying specific letters). In phase 2 (finished phase), participants were informed the PM task was completed. The non-new PM group continued only the ongoing task; the new PM group performed the ongoing task and a new PM task; and the implementation intention group performed the ongoing task and a new PM task encoded using the "if-then" strategy. The PM cues in phase 2 were different from those in phase 1. Data analysis included chi-square tests and ANOVA to compare commission error rates, accuracy, and reaction times across groups.

The chi-square test showed no significant difference in the proportion of participants making at least one commission error across the three groups. However, ANOVA on the commission error rate (excluding participants with no errors) revealed a significant difference among groups, F(2, 63) = 8.47, p = 0.001. Post-hoc comparisons showed that the new PM group had a significantly lower commission error rate than the non-new PM group (p < 0.01), and the implementation intention group had a significantly lower rate than the non-new PM group (p < 0.001). There were no significant differences among the groups in ongoing task accuracy or reaction time or reaction time to old PM cues. The implementation intention group showed significantly better accuracy on the new PM task compared to the new PM group, but reaction times were not significantly different.

The findings support the intention overwriting hypothesis, indicating that forming a new PM intention, especially with implementation intention encoding, reduces commission errors. This contrasts with some previous research suggesting that new PM intentions increase commission errors, possibly due to the similarity of old and new cues used in those studies. The current study used distinct cues, minimizing cue confusion. The reduction in commission errors might be due to the new intention overwriting the representation of the old intention, or potentially through retrieval-induced forgetting, where retrieving the new intention inhibits recall of the old intention. The lack of difference in ongoing task performance across groups suggests that the new PM tasks did not significantly increase attentional load. However, the focality of the PM cues and simplicity of the ongoing task might limit the interpretation of attentional effects.

This study demonstrates that forming a new PM intention can reduce commission errors, particularly when using an implementation intention strategy. The results support the intention overwriting hypothesis, suggesting a mechanism involving interference or retrieval-induced forgetting. Future research could explore the impact of varying delays between the completion of the old PM task and the initiation of the new PM task, and the influence of more demanding ongoing tasks on attentional resources and commission error rates.

The relatively simple ongoing task might have limited the detection of attentional effects. The use of focal PM cues could also have influenced the results. Future research with more complex ongoing tasks and varied cue focality is needed to fully understand the interplay between attention and intention overwriting in reducing commission errors. Additionally, a larger sample size might provide increased statistical power.