High-fidelity but hypometric spatial localization of afterimages across saccades.

Humans typically perceive their visual world as stable and continuous, despite frequent shifts of the retinotopic reference frame caused by saccades. This perceptual stability is paralleled by afterimage movement across saccades: Although retinotopically stable, afterimages appear to move in egocentric space wherever the eye moves. To investigate the mechanisms underlying this phenomenon, we tasked human observers to localize afterimages relative to briefly flashed probes in complete darkness. This psychophysical tracking of afterimages was accompanied by eye tracking, allowing us to fit a dedicated computational model to accurately predict afterimage movement based on the size of eye movements. The gain of afterimage movement was significantly hypometric, remained unaffected by postsaccadic visual feedback and saccadic adaptation, and was inversely related to saccade gain. Assuming a parsimonious framework of head-centered localization, afterimage movement is driven by efference-based, feedforward predictions of visual consequences of saccades, demonstrating the phenomenon's usefulness for studying perceptual stability.