Attentional Boost in Visual Working Memory? Concurrent Target Detection Enhances the Precision but Reduces the Retention Probability

Dual-tasking causes mutual interference between the two tasks. As an exception to this rule, performance in a memory task improves when participants perform a secondary task in which they detect the presence of a memory-task-unrelated target stimulus. The phenomenon is termed the attentional boost effect. A study using a change detection task has shown that attentional boost also occurs for working memory. In three experiments using a continuous-report task, we examined which aspect of working memory could be boosted by the concurrent target detection. In all experiments, the empirical measure of working memory accuracy, angular error between the probed color and reported color, showed dual-task interference, yielding less accurate memory when concurrent target detection was required than when it was not. However, the mixture-model analysis indicated that concurrent target detection enhanced the memory precision but reduced the probability of memory retention (i.e., increased random guessing) when the single-task and dual-task conditions were separated between blocks and when participants reported the presence of the target immediately as they detected it. These results suggest that differential proactive strategies to adjust working memory resources is responsible for the trade-off between the memory precision and retention probability and that attentional boost arises from an effort to minimize dual-task interference when the need of concurrent target detection can be expected in advance. The findings provide new insights into the paradoxical improvement of memory under a dual-task setting.