A (further) test of spontaneous serial refreshing in verbal and spatial working memory

Working memory is the cognitive system that keeps a limited amount of information temporarily accessible for ongoing cognition. One proposed mechanism to keep information active in working memory is refreshing. Refreshing is assumed to operate serially, reactivating memory items one by one by bringing them into the focus of attention during retention. We report two experiments in which we examine evidence for the spontaneous occurrence of serial refreshing in verbal working memory (Experiment 1, using letters as memoranda) and in visuospatial working memory (Experiment 2, using locations as memoranda). Participants had to remember series of red memory items, and black probes were presented between these memory items, with each probe to be judged present in or absent from the list presented so far, as quickly as possible (i.e., the probe-span task). Response times to the probes were used to examine whether the content of the focus of attention changed over time, as would be expected if serial refreshing occurs spontaneously during interitem pauses. Contrary to this hypothesis, our results indicate that the last-presented memory item remained in the focus of attention during the interitem pauses of the probe-span tasks. These findings confirm the boundary conditions of spontaneous serial refreshing that were previously observed for verbal working memory and extend them to visuospatial working memory. Implications for working memory maintenance are discussed.