Observations of Poggendorff Illusion in 3D Space without Physical Interaction between Line Segments and Inducing Rectangle

摘要

Visual illusion is purely reflecting the human visual mechanism and the studies on visual illusions can provide effective clues to reveal the human visual mechanism. In the present study, we had investigated the Poggendorff illusion and its variants in relation to the depth difference between the line element and the rectangle element with binocular viewing. In the classic Poggendoff illusion, two collinear segments abutting obliquely on a vertical rectangle could not be perceived collinear. Many studies on the Poggendorff illusion have been reported, but they only focus on the area near the junction considered playing important roles in causing this illusion. In this paper, interesting findings on a variant of the Poggendorff illusion were reported. In this variant, two collinear segments are arranged separately in two sides of a rectangle, namely without physical interaction between line element and rectangle element. Contrary to this variant, the classic Poggendorff illusion was called with physical interaction. We found that in the case without physical interaction Poggendorff illusion could be perceived as line element being placed at equidepth or farther depth than that of a rectangle element, but could not perceived as line element being at nearer depth than a rectangle element, which was the same phenomena as that occurred in the classic Poggendorff illusion. Furthermore, we found that the strength of Poggendorff illusion had a little or no change with increasing line depth when line segments were placed beyond inducing rectangle in the case without physical interaction, which was quite different from that the magnitude of the illusion was diminishing with increasing line depth in the case with physical interaction. We inferred that occlusions were working and causing this illusion in the case with physical interaction, but no occluding physically in the configuration without physical interaction; and it could not be made clear by conventional interpretation; therefore, the existence of some new factors, which could not be considered before, were expected. Moreover, we utilized Poggendorff illusion composed an illusory rectangle and a real line to investigate temporal properties on perception of 3D surface by changing displaying time sequence of illusory rectangle and real line. Experimental results are suggesting that perception of illusory surface takes bit more time than that for real surface; and perceptions of illusory surface and real surface are treated in different stage of visual systems. It is expected that the further investigation on these subjects can provide a new clue to reveal human visual mechanism.