WHEN WHERE THINGS ARE DEPENDS ON WHAT YOU’RE DOING: STIMULUS CONTROL REVERSES IMPLIED FRICITON EFFECTS IN SPATIAL PERCEPTION

  • Scott J. Jordan

Abstract

The perceived vanishing point of a moving stimulus is displaced beyond the actual vanishingpoint. Displacement decreases as the stimulus appears to move under implied friction (i.e., byitself, over a surface, or between two surfaces). The present experiment examined what wouldhappen if stimulus movements were controlled by the participant, not the computer. Asparticipants controlled the stimulus in conditions of increasing implied friction, thedisplacement actually increased. This reversal is consistent with economy-of-action effects inwhich variables such as perceived distance increase as the energy-requirements implied by thestimulus (e.g., a steeper hill) increase. What is unique about these findings is that the impliedeffort was virtual—the computer-generated stimulus only appeared to be under increasedfriction, and the behaviors required to control the stimulus (i.e., button presses) were exactlythe same in all conditions. These finding indicate spatial perception entails intentional, planningproperties and is, therefore, more than a mapping process regarding where things are.
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