Working memory contents enhance perception under stimulus-driven competition.

It is well known that attention is biased toward a stimulus matching working memory contents. However, it has been debated at which processing stage this memory-driven attentional bias takes place. While some studies show that memory-driven attention affects the early, perceptual stage of information processing, others argue that the finding showing such an effect is the result of working memory contents reducing uncertainty regarding the location of a target stimulus, without affecting the perception of the target. The present study tested whether a previous finding showing the perceptual effect of memory-driven attention is solely due to reduced target location uncertainty. We found that attentional bias by working memory contents affected the perception of a target stimulus, especially when multiple stimuli were present, competing against each other. This perceptual effect was not due to reduced target location uncertainty because the target location was always indicated by a response cue. Similar results were found regardless of whether working memory contents predicted the target location or not. These findings suggest that automatic, involuntary orienting of attention by working memory contents affects perception by resolving stimulus-driven competition.