Abstract
The Horizontal-Vertical illusion is a phenomenon in which participants underestimate the length of horizontal lines when compared to vertical lines of the same length (Yang, Dixon, & Proffitt, 1999). The illusion is traditionally thought of as only a visual phenomenon in geometric tasks. The present project sought to demonstrate that the illusion occurs in haptic perception as well. Three groups of participants provided matching judgments in three conditions: (1) haptic perception with visual matching, (2) visual perception with visual matching, and (3) combined visual and haptic perception with visual matching. In condition (1), participants haptically manipulated vertically positioned wooden dowels of various lengths, then attempted to match the length of the dowel with a horizontal pulley system positioned frontally with respect to the participant. In condition (2), participants viewed vertically positioned wooden dowels of various lengths, then attempted to match the length of the dowel with a horizontal pulley system positioned frontally with respect to the participant. In condition (3), participants both viewed and were permitted to manipulate through wielding vertically positioned wooden dowels of various lengths and then attempted to match the length of the dowel with the same pulley system used in conditions 1 and 2. Results indicated no differences between the three experimental conditions: haptic, vision, and combined (haptics and vision). Regardless of condition, participants underestimated the dowel length in the horizontal orientation. The current experiment offers support for the Horizontal-Vertical Illusion affecting the haptic system. Additionally, the lack of differences between experimental conditions offers support for Gibson's (1979) theory of equivalence in perceptual systems.
Meeting abstract presented at VSS 2017