Spatial Independency in Perceived Lengths of Saccade-induced Images

When observers make a saccade across a flickering light dot at the same location, they usually perceive an array of dots (Hershberger, 1987). This phenomenon can be exploited for presenting two-dimensional images using only a single dimensional light source such as a single column of LEDs or laser projectors. In the present study, we investigated whether the perceived length of saccade-induced images is modulated by relative position of the light source and the observer. Participants were presented with a continuous laser-lit dot at several different locations adjacent to a saccade target. On each trial, they were required to make a saccade from a fixation point to the saccade target and then to localize the two endpoints of perceived line induced by the saccade. The results showed that the perceived length of the saccade-induced lines was approximately a half of the distance between the fixation point and the saccade target regardless of the light source location.