| Summary: | Revesz (1934 Zeitschrift fur PsychologieBd . 1, Kap 20) and Bean (1938 Journal of Experimental Psychology 22 283–289.) reported almost all the geometrical optical illusions existed in a tactual mode. Such a study can examine theories of visual illusions with modality-free theories. A number of articles have been devoted to the theory that repeated judgments decline the magnitude of visual illusion. In the current study, we examine whether repeated judgments decline the magnitude of geometrical haptic illusion. The Fick illusion (i.e., a horizontal vertical illusion) was investigated. A graphics Braille display with 32×48 dots was used to present an inverted T haptically without vision. The horizontal line was consistently 49.2 mm long, and the vertical line was varied in each trial. Three subjects with normal sight participated. They judged which line was longer than the other. The point of subjective equality at which the subject perceives the two lines to be the same was measured using the method of constant stimuli. In the first session the mean PSE was about 13%; to compensate for the illusion, the vertical line must be set physically shorter than the horizontal line. We found that repeated judgments produced a reduction in illusion magnitude and dissolved the illusion entirely.
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