Further Evidence for the Division of Attention Among Non-contiguous Locations

Abstract

Models of visual attention have, with few exceptions, suggested that attention is deployed to unitary regions of visual space. Kramer and Hahn (1995) recently reported that attention is considerably more flexible than previously believed, such that under some conditions attention may be focused on multiple non-contiguous areas of the visual field. In the five studies reported here, we examined the boundary conditions on the ability to divide attention among different locations in visual space. In each of the studies, subjects performed a same-different matching task with target letters that were presented on opposite sides of a set of distractor letters. Experiments 1, 2 and 3 provide further support for our proposal that subjects can concurrently attend to non-contiguous locations as long as new objects do not appear between the attended areas. Experiment 4 examined whether the disruption of multiple attentional foci was the result of the capture of attention by new objects per se, or by task-irrelevant objects. Multiple attentional foci could be maintained as long as new distractor objects did not appear between target locations. Experiment 5 examined whether attention can be divided among non-contiguous locations within as well as between hemifields. Hemifield boundaries did notconstrain subjects' ability to divide attention among different areas of visual space. The results of these studies are discussed in terms of the nature of attentional flexibility and putative neuroanatomical mechanisms which support our ability to split attention among different regions of the visual field.