Abstract
The dissociations between visual perception and visual guided action have long been suggested (Goodale & Haffenden, 1998). Studies showed that the saccadic eye movements were guided by real physical stimuli rather than by the perceived visual illusions. In the present research, we explored which guides the pursuit eye movements, physical stimuli or visual illusions. In the case of Hering illusions, where radiant lines induce a perceived curvature for a physically straight line, a ViewPoint PC60 video eye tracker was used to record the eye movements during observers pursuing a red dot target moving along a straight line, a Hering illusory curve (physically a straight line), or a curve with curvature match the Hering illusion. The results showed that the eye scanning paths of pursuing a target moving alone an illusory curve are more similar to those of viewing a real curve than to those of viewing a straight line, what the illusory curve is physically. This suggested that the visual illusion guides the pursuit eye movements in the case. We then applied similar paradigm to test the Wundt, Müller-Lyer, and Ebbinghaus illusory patterns, which exhibited illusory curvatures, line segment lengths, and sizes, respectively. By analyzing the gaze paths of pursuing targets moving along those illusory rails, we found that the scanning paths followed the illusory rather than the real physical patterns. The results suggested that pursuit eye movements may be guided by the what rather than by the how visual information processing streams.
NSC 98-2410-H-034 -036 National Science Council Taiwan.