Forgetting no-longer-relevant prospective memory intentions is (sometimes) harder with age but easier with forgetting practice

In young adults, it has been shown that prospective memory (PM) commission errors, the erroneous performance of a previously relevant intention, are less likely for repeatedly performed intentions (than never performed intentions). We examined whether this pattern holds for older adults, for whom impaired response inhibition processes might heighten risk of commission errors for repeatedly performed PM intentions. Older adults encoded a PM intention to press a key when a target word appeared during an ongoing lexical decision task. Target words were presented 4 (repeatedly) or 0 times before participants were instructed the PM task was finished and should not be performed again. Target words were then (re)presented and commission errors were recorded. Experiment 1 demonstrated it was easier for older adults to forget (deactivate) a PM intention that was performed repeatedly (4-target condition) than one that was never performed (0-target condition). However, older adults were more likely to make commission errors than young adults in the 4- but not the 0-target condition. Experiments 2 and 3 examined whether distinct strategies reduce commission errors. Whereas a preparatory instructional strategy produced inconsistent effects, forgetting practice was highly effective in producing floor levels of commission errors for older and young adults in the 4-target condition. Findings are interpreted within the dual-mechanisms account of PM commission errors, which highlights the interplay of spontaneous retrieval and cognitive control in the forgetting of previously relevant intentions. Practically, the findings provide first evidence of a translational strategy that older adults may use to minimize commission errors.