Flexible attention allocation dynamically impacts incidental encoding in prospective memory

Remembering to fulfill an intention at a later time often requires people to monitor the environment for cues that it is time to act. This monitoring involves the strategic allocation of attentional resources, ramping attention up more in some contexts than others. In addition to interfering with ongoing task performance, flexibly shifting attention may affect whether task-irrelevant information is later remembered. In the present investigation, we manipulated contextual expectations in event-related prospective memory (PM) to examine the consequences of flexible attention allocation on incidental memory. Across two experiments, participants completed a color-matching task while monitoring for ill-defined (Experiment 1) or specific (Experiment 2) PM targets. To manipulate contextual expectations, some participants were explicitly told about the trial types in which PM targets could (or not) appear, while others were given less precise or no expectations. Across experiments, participants' color-matching decisions were slower in high-expectation trials, relative to trials when targets were not expected. Additionally, participants had better incidental memory for PM-irrelevant items from high-expectation trials, but only when they received explicit contextual expectations. These results confirm that participants flexibly allocate attention based on explicit trial-by-trial expectations. Furthermore, the present study indicates that greater attention to item identity yields better incidental memory even for PM-irrelevant items, irrespective of processing time.