Abstract
While most research has examined foveal vision using stimuli with a sudden onset, natural viewing is an active process where objects are bought to the fovea based on a peripheral preview of the saccade target. Recent behavioral and neuroimaging studies have revealed robust changes in foveal target processing when the target is available extrafoveally before the saccade (i.e., the extrafoveal preview effect). To further characterize the role of peripheral vision, we measured the preview effect for stimuli that varied in eccentricity and added noise. Using a gaze-contingent paradigm, an upright/inverted face was presented 8, 11, or 14 degree in the periphery while participants fixated at a central cross. This preview was followed by a cue prompting participants to make a saccade to the extrafoveal face, during which the face changed on 50% of trials to the opposite orientation, making the preview invalid. Participants then indicated the tilt direction of the briefly presented foveal face. Faces were displayed with a 0, 20%, or 40% noise mask, and face visibility was operationalized by a lateralized face identification task, run in a separate session. As expected, we replicated the extrafoveal preview effect, at least for the nearby faces. Discrimination performance was significantly enhanced in the valid versus invalid preview condition. Planned comparisons revealed that this validity effect did not occur in all visibility conditions, showing that the noise and eccentricity manipulations did influence the preview effect. This was confirmed with a mixed model analysis. In addition, we found that a validity effect on gaze behavior: first fixation duration of the saccade target decreased and total number of saccades increased for invalid trials. Overall, these findings constrain theories of how preview effects might influence perception in natural viewing conditions.