Investigating temporal properties of covert shifts of visual attention using the attentional walk task.

The attentional walk task was used to investigate the temporal properties of covert shifts of attention. Observers shifted attention within arrays of identical items in response to a series of auditory commands and reported the color of the final disk. The density of the arrays and the timing of the shift commands varied. Performance decreased as density increased, and the minimal amount of time needed to shift attention depended on the density of the display, varying from 350 to 750 msec. In addition, the observers were able to maintain attentional focus for at least 3,500 msec without a decline in performance, regardless of density. Thus, although the ability to maintain attention at a given position was found to be independent of the precision with which that location was defined, more precise attentional shifts required more time to execute.