Task Interference in Prospective Memory: Adopting a Retrieval Mode and Checking for Targets

Embedding a prospective memory task in an ongoing activity can interfere with performance of that ongoing activity. One explanation of this task interference is that it entails (a) adopting a retrieval mode or readiness to encounter the targets that indicate when to perform the intended action and (b) checking the environment for those targets. An experiment using a new method is reported and provides evidence for these processes. On control trials, participants performed just the ongoing activity (a short-term memory task combined with a 4-choice RT task). On experimental trials, a prospective memory task (press the Enter key if certain words appear in the short-term memory task) was embedded in the ongoing activity. Evidence for adopting a retrieval mode came from finding slower RT task performance on control trials when participants had already been instructed about the prospective memory task than when they had not yet been so instructed. Evidence for target checking came from finding slower RT task performance on experimental trials when a target could appear in any one of five locations than in just one location.