Adaptive Cognitive Control in Prospective Memory

Event-Based Prospective Memory (PM) requires performing a planned action upon encountering a target event. The PM decision control (PMDC) model quantifies the dual mechanisms of cognitive control (proactive and reactive, Braver, 2012) that support PM. Here, we test a key prediction of the dual-mechanisms theory: that cognitive control will shift from proactive to reactive as the need for control lessens due to PM targets being infrequent. Participants made lexical decisions (ongoing task) and were presented blocks of trials which either contained no PM targets, a high PM target frequency (19% of trials), or a low PM target frequency (5%). We fit the behavioural data with an extended version of PMDC that was augmented to specify the ongoing-task habituation and PM learning dynamics required to account for the way in which participants adapted their behaviour as a function of task practice and expected PM target frequency. PM costs (ongoing task response slowing in PM conditions relative to no PM target condition) were observed only in the high frequency condition, explained by PMDC by an increase in proactive control. PM accuracy was similar across high and low frequency conditions early in the experiment, but later an advantage emerged for the lower frequency PM task. PMDC accounted for this with stronger reactive control in low frequency condition that increased over practice. Our results confirm the prediction that control shifts from proactive to reactive with lower target event frequency, respond to recent calls from the PM literature for theory to account for across-trial dynamics.