Toward a Better Understanding of Costs in Prospective Memory: A Meta-Analytic Review

In prospective memory (PM) research, a common finding is that people are slower to perform an ongoing task with concurrent PM demands than to perform the same task alone. This slowing, referred to as costs, has been seen as reflecting the processes underlying successful PM. Historically, costs have been interpreted as evidence that attentional capacity is being devoted toward detecting PM targets and maintaining the intention in working memory; in other words, the claim is that participants are monitoring. A new account, termed delay theory, instead suggests that costs indicate a strategic speed/accuracy adjustment in favor of accuracy, allowing more time for PM-related information to reach its own threshold. Taking a meta-analytic approach, we first review studies in the PM literature that have reported ongoing task performance, both with and without a concurrent PM task, identifying key factors suitable for the meta-analysis. Next, we analyze the data of these studies, using our factors as moderators in a series of metaregressions, to determine their impact on the presence or magnitude of PM-related costs. Finally, we interpret the results of the meta-analysis from both monitoring and delay perspectives in an effort to better understand the nature of costs and what they reflect about the underlying cognitive processes involved in PM.