Influence of direction of attention upon saccade-contingent visual mislocalization of a flashing target

Abstract

In complete darkness, the subject made a saccade from the central flashing target to the saccade target positioned 10 deg to the right. The subject was asked to observe the phantom lights of the flashing target. The target was extinguished various points in time after saccade onset. The subject reported the final perceived flash position using the probe stimulus. The attention was voluntarily directed toward the saccade target (ST), fixation point (FP), or phantom lights (PL), through the saccade. The time course of the localization of the final phantom light was much different from the attention-directed position. In the ST-attended condition, all of the three subjects observed the final phantom light near the saccade target consistently. That is, the flashing target was largely mislocalized toward the saccade goal. In the FP-attended condition, the degree of mislocalization was significantly smaller than that of the ST-attended condition. In the PL-attended condition, the degree of mislocalization changed within 20 or 40 ms from saccade onset smoothly. The smooth displacement of mislocalization supported the speculation of Ebisawa. That is, the attempt to observe the phantom flashes, which showed the apparent motion, produced the smooth attention shift, this yielding the smooth displacement of mislocalization.