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Abstract

De Valois and De Valois (1991 Vision Research 31 1619-1626) showed that moving Gabors (cosine gratings windowed by a stationary 2-dimensional Gaussian envelope) are locally misperceived in their direction of motion. In a pointing task, Yamagishi, Anderson and Ashida (2001 Proceedings of the Royal Society 268 973-977) reported even stronger visuo-motor localization error especially when participants had to make a speeded response.
Here, we examined motion-induced bias in the context of an active navigation task, a situation in which perception and action are tightly coupled. Participants were presented with a birds-eye view of a vertically moving contour that simulated observer motion along a path. Observers centrally fixated while the path and a moving Gabor target were presented peripherally. The task was to follow the path with the moving Gabor, whose position (left/right) and direction(towards left/right) were varied in separate blocks. Gabor eccentricity was constant relative to fixation, with observers adjusting their simulated position with a joystick. Deviations from the path were analyzed as a function of Gabor direction. We found large and consistent misalignment in the direction of the moving
Gabor, indicating that global position/motion judgments during action can be strongly affected by irrelevant local motion signals.