The Hering Illusion has not been widely studied in recent years. Coren (1970) investigated the role of lateral inhibition. A.W. Pressey (1971) experimented with the acute angles formed by the radial lines. He showed that when dots are placed where the solid line had been, the illusion still remaines. A different factor which may be important is the end points of the radial lines. Of particular interest are the subjective contour lines formed by the end points. By adjusting the lengths of the radial lines, we can control the shape of this contour. We hypothesized that parallel contours would elicit a greater perception of curvature in the illusion.

Methods:The subjects used were eighteen Alma College students. The stimuli were presented to the subjects on a computer screen using the Eye Lines software created by Dr. Walter Beagley. There were four different stimuli presented to each subject. In trial 1 the end points of the radial lines formed convex subjective lines. In trial 2 the end points of the radial lines formed parallel subjective lines. In trial 3 the end points of the radial lines formed concave subjective lines. In trial 4 the end points of the radial lines form no subjective lines. The subjects were instructed to adjust two parallel lines below each stimuli so they appeared to have the same curvature as those parallel lines in the illusion. The Eye Lines program measured the differences in adjustment. Refer to Figure 1 for representatives of stimuli used.

Figure1: stimuli used

Results:The convex, parallel, and variable stimuli all produced similarly large amounts of perceived curvature. The concave stimulus produced significantly less. Figure 2 shows these results in terms of maximum adjusted displacement.

Discussion: With similar results from the convex, parallel, and variable subjective line stimuli we concluded, in this experiment, these were not substantial determinants of the Hering Illusion. The stimuli which produced the least amount of perceived curvature was the concave subjective line contour. We have attributed this decrease in perceived curvature in the Hering Illusion to the cancelling effect of the concave subjective lines. We suggest because the radial lines in each stimulus were of the same origin and the acute angles formed by the radial lines were the same, the end points of the radial lines which formed the subjective contours contributed to the results.

References:

A.W. Pressey. (1971) An Extension of the Assimilation Theory to Illusions of Size, Area, and Direction. Perception & Psychophysics 9, 172-176.

Coren, S. (1970) "Lateral Inhibition and the Wundt-Hering Illusion." Psychonomic Science 18, 341.

More Posters

Web Posters from other courses and projects

Alma College Psychology Department