Abstract

Navigation in the environment relies, in part, on the visual system to differentiate self-motion from that of other objects. Research examining the way in which the brain is able to visually disentangle forward locomotion from eye motion, for example, suggests that the brain may have an eye movement compensation mechanism. Other findings, however, question the existence of this mechanism in that the previously reported illusory shift in the focus of expansion (FOE) may be due to induced motion. Yet, this alternative hypothesis may need to be revised in order to account for the perception of straight, radial trajectories as curved. In order to understand the conditions under which this trajectory illusion exists, the current investigation examined the role of induced motion, radial speed gradient, and smooth pursuit eye movements (SPEM). Results suggest that the strength of the illusion relies on induced motion and SPEMs, thereby implicating that the role of eye movements in the illusory FOE shift needs to be taken into consideration.