FIG. 1.

Task setup. Targets were back-projected onto a translucent screen. Each trial began with the presentation of a green fixation spot at center that randomly lasted for 500–1,000 ms. Next, a red cue was flashed for 30 ms either 30° left or right of fixation, aligned vertically with the fixation spot. After a variable delay (corresponding to stimulus-onset asynchronies [SOAs] of 50, 100, 200, 500, and 1,000 ms), a red target was presented at the congruent or incongruent position (randomly determined), also 30° left or right of fixation for 1.5 s. Subjects were asked to ignore the noninformative cue and to make a rapid combined head–eye gaze movement to the target as soon as they saw it. A black screen signaled the end of the trial. The intertrial interval (ITI) lasted 2 s.