Tactual and visual illusions in the T-shaped figure.

Abstract

A. G, Experiments on sensory-tonic field theory of perception: VII. Effect of asymmetrical extent and starting position of figures on the visual apparent median plane.

Stimulus configuration and line orientation in the horizontal-vertical illusion

“…Kunnapas (1955a) and Tedford and Tudor (1969) found a negative HVI with the side-T figure, while Finger and Spelt (1947) and the present study found a small, but positive, HVI with this figure. Several differences in experimental design and stimulus conditions are correlated with the difference.…”

“…He inferred that these results indicated the effects of two illusions in his figures, an overestimation of the vertical line and an overestimation of the dividing line. He suggested that the latter effect was variable, depending upon the point of intersection, and that the two illusions summated in the T and inverted T but opposed one another in the side T. Tedford and Tudor (1969) and Finger and Spelt (1947) also compared the inverted and side-T figures. Both confirmed that the inverted T yielded a greater illusion than the side T. In agreement with Kunnapas, Tedford and Tudor found a reversal of the illusion with the side T (i.e., a greater divided-line illusion), while Finger and SpeIt found a small, but positive, illusion (a greater HVI).…”

Attenuating the haptic horizontal—vertical curvature illusion

“…In the second experiment, we sought to further examine the impact of relevant factors by rotating the curves 90º to the right. The effect of the positive rotation was to prompt radial scanning of the bases of curves and eliminate most of this forward-and-back arm motion during scanning for the rotated curved lines themselves (see also Künnapas, 1955;Tedford & Tudor, 1969). In vision, rotation of an inverted-T shape makes the continuous line horizontal and yields overestimation of the horizontal.…”

Mechanisms in the haptic horizontal-vertical illusion: Evidence from sighted and blind subjects

“…Day and Avery linked the inverted-T illusion to bisection, since the divided line in the inverted T was judged as shorter than the continu" ous vertical segment. Bisection was pitted against radial-tangential effects in a study by Tedford and Tudor (1969). They reported that the illusion was altered by orientation when a 90°rotation made the continuous line segment horizontal rather than vertical.…”