Abstract
The gaze control system ought to inhibit saccades under two conditions. On the one hand, saccades should be inhibited when the sudden onset of stimuli threatens to capture attention and divert gaze. On the other hand, saccades should also be suppressed when task-relevant information accrual is ongoing and vulnerable to disruptions in movements of gaze. These two goals need not be mutually exclusive. In order to examine the time course of verbal-to-sensory translation in a reverse Stroop color search task, we delayed onset of target colors by 200, 300 or 400 msec. The result was clear saccadic inhibition that was time-locked to the onset of the color targets. Secondarily, there was little evidence of any saving from the initial presentation of the verbal specification of the target (a color word): For each additional 100 msec of delay of the search targets, there was a corresponding additional delay of 75 msec in response time. In order to reduce saccadic suppression due to the sudden onset of the search array, we employed gradual color changes of initially uniformly gray targets. When initiation of the color fades was consistently delayed by 400 msec, there was still evidence of saccadic suppression during the fade-in of the coloration of the targets, and only partial savings in response times. However, reverse Stroop interference was eliminated in this case. Presumably the delayed presentation of the search array allowed strategic re-encoding (translation) of the verbal information into a searchable sensory code. Whereas saccadic inhibition that was due to sudden onsets was accompanied by disruptions of cognitive processing, saccadic inhibition due to information accrual was not.
Swarthmore College Faculty Research Grant, HHMI.