Explicit eye movements failed to facilitate the precision of subsequent attentional localization

This study investigated the usefulness of explicit spatial coordinates from eye movements for the precision of covert shifts of attention within dense arrays of items. Observers shifted their attention covertly from one item to the next in response to a series of beeps and reported the color of the disc on which the series ended, providing an estimate of the accuracy of the "attentional walk". We compared performance in this task when only covert shifts of attention were done to performance when observers first executed an explicit eye movement to the starting point of the attentional walk before beginning the covert attentional walk. The hypothesis was that the eye movement would activate explicit coordinates of the starting point of the attentional walk within brain systems that are involved in controlling both shifts of attention and eye movements. This in turn would provide an anchor for the attentional walk, thereby improving performance. The evidence did not support this hypothesis. Performance was no better with an explicit eye movement prior to the attentional walk than without one. This suggests that covert orienting--shifting attention--and overt orienting--shifting the eyes-access the same coordinate system and therefore activating new coordinates interferes with the old ones, no matter what the system of orienting is.