Stop before you saccade: Looking into an artificial peripheral scotoma.

Abstract

We investigated whether adults with healthy vision can move their eyes toward an informative target area that is initially hidden by a gaze-contingent scotoma in the periphery when they are under time pressure. In the experimental task, participants had to perform an object-comparison task requiring a same-different judgment about two silhouettes. One silhouette was visible, whereas the other was hidden under the scotoma. Despite time pressure and the presence of the visible silhouette, most participants were able to move their eyes toward the informative region to reveal the hidden silhouette. Saccades to the hidden stimulus occurred when the visible stimulus was presented directly opposite in either fixed or variable locations and when the visible stimulus was presented at an adjacent location. Older participants were also able to perform this task. First saccades in the direction of the hidden stimulus had longer latencies compared with saccades toward the visible stimulus. This suggests the use of a deliberate, nonreflexive saccade strategy ("stop before you saccade"). A subset of participants occasionally made curved saccades that were aimed first toward the visible stimulus and then toward the hidden stimulus. We discuss the implications of our findings for patients who have a biological scotoma, for example, in macular degeneration.