Dissociation between perception and saccadic localization in the Frame Effect

A moving frame can act as a positional reference for the objects that it surrounds. When a frame moves back and forth on the screen, briefly flashed stimuli appear displaced. This illusory shift can be as large as the distance the frame moves, making it one of the most significant position shift illusions. The frame effect persists under many variations of the frame’s shape and motion trajectories, suggesting a position encoding mechanism that relies on relative location rather than motion. With one exception (the double-drift), motion-induced position shifts produce similar effects on saccadic eye movements and perception. Here, we compare the effect of a moving frame on perception and on saccades across spatial and temporal variations of the frame and the probe. The first experiment showed that saccades targeting the probes were displaced by only about a third of the shift seen for the perception of the probe. A second experiment showed that this difference was constant across a large range of frame speeds. These results add novel evidence in support of dissociable position representations for perception and action.