Splitting the beam: Distribution of attention over noncontiguous regions of the visual field

In an effort to examine the flexibility with which attention can be allocated in visual space, we investigated whether subjects could selectively attend to multiple noncontiguous locations in the visual field. We examined this issue by precuing two separate areas of the visual field and requiring subjects to decide whether the letters that appeared in these locations matched or mismatched while distractors that primed either the match or mismatch response were presented between the cued locations. If the distracters had no effect on performance, it would provide evidence that subjects can divide attention over noncontiguous areas of space. Subjects were able to ignore the distracters when the targets and distracters were presented as nononset stimuli (i.e., when premasks were changed into the targets and distracters). In contrast, when the targets and distractors were presented as sudden-onset stimuli, subjects were unable to ignore the distractors. These results begin to define the conditions under which attention can be flexibly deployed to multiple noncontiguous locations in the visual field.