Predicting what and when across saccades: Evidence from the extrafoveal preview effect.

In order to fully process items of interest, we use information from outside the fovea to plan the target of the next saccadic eye movement. There is growing evidence that our initial preview of the identity and features of the saccade target, prior to bringing it to the fovea using the saccade, is used to make our subsequent post-saccadic processing more efficient. However, the mechanisms underlying trans-saccadic previews remain unknown. We investigated this in a gaze-contingent preview paradigm in which a face stimulus either remained the same ("valid preview") or changed ("invalid preview") during the saccadic eye movement. On some trials, a brief blank gap was added at the beginning of the new fixation, before the face was presented at the fovea. Although the expected preview benefit was found when the face stimulus was present after the saccade, the addition of the blank period eliminated the preview effect. Our results suggest that the preview effect relies on a sensorimotor prediction about both "what" will be present at the fovea after the saccade and "when" the new fixation will begin. These findings provided further evidence for an active, predictive mechanism for trans-saccadic perception.