When a visual stimulus is continuously moved behind a small stationary wind
ow the window appears displaced in the direction of motion of the stimulus.
In this study we showed that the magnitude of this illusion is dependent o
n (i) whether a perceptual or visuomotor task is used for judging the locat
ion of the window: (ii) the directional signature of the stimulus, and (iii
) whether or not there is a significant delay between the end of the visual
presentation and the initiation of the localization measure. Our stimulus
was a drifting sinusoidal grating windowed in space by a stationary, two-di
mensional, Gaussian envelope (sigma =1 cycle of sinusoid). Localization mea
sures were made following either a short (200 ms) or long (4.2 s) post-stim
ulus delay The visuomotor localization error was up to three times greater
than the perceptual error for a short delay However: the visuomotor and per
ceptual localization measures were similar for a long delay Our results pro
vide evidence in support of the hypothesis that separate cortical pathways
exist for visual perception and visually guided action and that delayed act
ions rely on stored perceptual information.