Effect of stimulus orientation upon haptic perception of the horizontal-vertical illusion.

Abstract

The effect of orientation upon haptic perception of the L and T figures presented in S's frontoparallel plane and in a horizontal plane in front of him was investigated. The data confirm the importance of the section effect and suggest that this effect is independent both of the inclination of the stimulus within a plane and of the plane within which it is presented. A theoretical curve showing the relationship between the radial and tagential components of haptic exploration was derived and found, prima facie, to provide a satisfactory approximation to the data. 1 We wish to acknowledge the assistance of Rosalind Heaton in collecting the data.2 Requests for reprints should be sent to J.

Muscular Torque Can Explain Biases in Haptic Length Perception: A Model Study on the Radial-Tangential Illusion

“…For example, the r-t illusion was found to be larger for inverted-T-figures than for Lfigures (e.g., [9,17,18]; but see also [7]). This difference was found to result from the underestimation of bisected stimuli ( [18]).…”

“…Our analysis consists of a qualitative comparison between patterns of biases predicted from the model, with patterns of biases reported in the literature. We will do so for three different studies ( [7][8][9]…”

“…Deregowski and Ellis ( [9]) demonstrated that the magnitude of the r-t illusion depends on stimulus orientation. In Experiment 1, they presented an L-figure at 7 orientations: 0°, 15°, 30°, 45°, 60°, 75°, and 90° relative to the body-midline.…”

“…Whole-arm movements induce large perceptual biases, whereas finger-and-hand motions alone induce no bias ( [7]). Furthermore, for whole-arm movements the strength of the illusion varies with stimulus length (e.g., [7,8]) and stimulus orientation ( [8,9]). …”

Dynamic properties of radial and tangential movements as determinants of the Haptic Horizontal-Vertical Illusion with an 'L' figure.

“…The effect operates regardless of the spatial separation of the two extents to be judged (Cheng, 1968) and independently of two different types of movement involving different joints and muscle groups (Day & Wong, 1971). As radial movements are specific to the horizontal plane, no relative overestimation of haptic extent is found when the L figure is presented in the vertical (fronto-parallel) plane (Cheng, 1968;Day & Avery, 1970;Day & Wong, 1971;Deregowski & Ellis. 1972).…”