Re-examining the contribution of visuospatial working memory to inhibition of return

Castel and colleagues (Percept Psychophys 65(6):970-981, 2003) proposed that visuospatial working memory is needed to retain and update the irrelevant but attended location in an inhibition of return (IOR) procedure. In a series of three experiments, we re-examined this hypothesis by loading visuospatial working memory and manipulating the timing of encoding. When the visuospatial memory items were presented right after the cue, as in Castel et al. (Percept Psychophys 65(6):970-981, 2003), we replicated the lack of IOR in the dual-task condition (Experiment 1). However, when we presented the visuospatial memory items before the spatial cue, to control for retroactive interference in encoding, we found robust IOR effects (Experiment 2); the effect remained strong even when participants were prevented from using verbal labels to rehearse the memory material (Experiment 3). We conclude that IOR does not seem to depend on retaining the position of the irrelevant cue in visuospatial working memory.