Search

Observers can voluntarily select which items are encoded into working memory, and the efficiency of this process strongly predicts memory capacity. Nevertheless, the present work suggests that voluntary intentions do not exclusively determine what is encoded into this online workspace. Observers indicated whether any items from a briefly stored sample display had changed. Unbeknown to observers, these changes were most likely to occur in a specific quadrant of the display (the dominant quadrant). Across 84 subjects and 5 groups of observers, change detection accuracy was significantly higher for items in the dominant quadrant, suggesting that memory encoding was biased towards the dominant quadrant. Only 9 of the 84 subjects were able to correctly specify the dominant quadrant when asked whether any location was more likely to contain the changed item, but more sensitive forced-choice procedures did reveal above-chance discrimination of the dominant quadrant. Nevertheless, because forced choice performance was unrelated to the size of the bias and no observer reported a biased encoding strategy, the bias was unlikely to depend on voluntary encoding strategies. The encoding bias was not due to a reduction in the response threshold for indicating changes in the dominant quadrant (Experiment 2). Finally, separate measures of the number and resolution of the representations in memory suggested that encoding was biased in a discrete slot-based fashion (Experiment 3). That is, although items in the dominant quadrant were more likely to be encoded into memory, mnemonic resolution for the favored items was not affected. Keywords: working memory, encoding, statistical learning DOI: 10.1037/a0019324

Models of attentional control usually describe online shifts in control settings that accommodate changing task demands. The current studies suggest that online control over distractor exclusion--a core component of visual selection--can be accomplished without online shifts in top-down settings. Measurements of target discrimination accuracy suggested that the degree of distractor exclusion was guided by retinotopic maps of the prior probability of distractor interference at the attended locations. These probability maps can be retrieved via object-based cues, and they interact with shifts of attention to elicit increased levels of distractor exclusion when it is most needed. Thus, static probability maps can provide an internal template that guides the resolution of visual interference as spatial attention traverses the visual field.

Larger benefits of spatial attention are observed when distractor interference is prevalent, supporting the view that spatial selection facilitates visual processing by suppressing distractor interference. The present work shows that cuing effects with identical visual displays can grow substantially as the probability of distractor interference increases. The probability of interference had no impact on spatial cuing effects in the absence of distractors, suggesting that the enlarged cuing effects were not caused by changes in signal enhancement or in the spatial distribution of attention. These findings suggest that attentional control settings determine more than where spatial attention is directed; top-down settings also influence how attention affects visual processing, with increased levels of distractor exclusion when distractor interference is likely.