Parametric integration of visual form across saccades

Through saccadic eye movements, the retinal projection of an extrafoveally glimpsed object can be brought into foveal vision quickly. We investigated what influence visual detail collected before the saccade exerts on the postsaccadic percept. Participants were instructed to saccade towards a peripheral stimulus, and to indicate on a continuum of ellipses with varying aspect ratios which exact shape they had perceived to be present after saccade landing. Compared to both an identical ellipse preview and a qualitatively different square preview, a quantitatively different ellipse preview was observed to shift the mean postsaccadic percept towards the presaccadic aspect ratio parameter value. This integration of subtly different form information was accompanied by an integration of the identity of both stimuli presented: In the great majority of these trials, subjects indicated that they had not noticed the occurrence of a change to the stimulus. When a blank screen preceded the postsaccadic stimulus onset the influence of presaccadic stimulus information on postsaccadic perception was weaker. An immediate postsaccadic mask on the other hand abolished the effect entirely. We conclude that integration of parametric visual form information occurs across saccades, but that it relies on a quickly decaying and maskable visual memory.