The Horizontal-Vertical Velocity Illusion: Implications for the Design of Dynamic Displays

Abstract

It has long been known that physically equivalent vertical and horizontal stimuli are often perceived as different. The present study examines this phenomenon in the context of motion perception. Participants were asked to judge the speed of stimuli moving in vertical and horizontal directions using the method of constant stimuli. The findings are consistent with previous research in that vertically moving stimuli appear to move relatively faster than horizontal stimuli traveling at the same speed. Further, the axis of focus, i.e., horizontal or vertical, used as the standard for comparison of the two relative velocities, appears to mediate the perceived velocity of the vertically ascending and vertically descending stimuli. These findings may have important implications for the design and implementation of displays that use a combination of both horizontal and vertical indicators.