Abstract
According to biased competition models, spatial attention facilitates target discrimination by protecting the processing of attended objects from distractor interference. Supporting this view, the relative improvement in visual processing at attended locations relative to unattended locations is substantially larger when the display contains distractor interference. The present research shows that even when the level of distractor interference and the attended locations are held constant, spatial cueing effects can vary dramatically as a function of the context in which a trial is presented. When there was a high probability of distractor interference, spatial cueing effects were significantly enlarged relative to a condition in which distractor interference was less likely. This context-driven modulation of the spatial cueing effects was restricted to trials that contained distractor interference; with displays that contained no distractors, spatial cueing effects were unaffected by the probability of distractor interference. This interaction of display and context suggests that the context effect is not a result of changes in the level of signal enhancement at the attended locations. A change in signal enhancement should be evident even in the absence of distractor interference. Instead, we suggest that a high probability of distractor interference stimulates a top-down increase in the degree of distractor exclusion at the attended locations. While a number of studies have shown that observers have top-down control over where spatial attention is directed, these studies provide new evidence of top-down control over how visual processing is affected at the attended locations.