Abstract
Humans change their point of gaze thousands of times per day, redirecting the high-resolution fovea to objects of interest previously viewed in the periphery. Is peripherally viewed information merely used to redirect gaze, or are the two sources of information integrated to improve performance possible from either view alone? We examine this question for orientation discrimination. Method. Observers viewed a small grating patch either in the periphery prior to a saccade, in the fovea after saccading to it, or both. The task was orientation discrimination relative to the vertical. Contrast was reduced during the saccade to equate peripheral and foveal performance. Results. Performance was better with two views than with either view alone, indicating integration across the saccade. A perturbation method (rotating the foveal relative to the peripheral grating) showed that the two orientation estimates were averaged, the weights depended on the reliability of each estimate, and the weight on the foveal estimate was higher than predicted by the ideal observer. A similar result was obtained if the foveal view occurred first, followed by a saccade away from the patch. The saccade was required for integration; there was no evidence of integration with the same sequence of retinal views without the intervening saccade.
Conclusion. Humans integrate orientation information across saccades, giving priority to the foveal view. This is consistent with observers using a prior distribution on cue reliability that expects foveal to have higher acuity than peripheral information, as is usually true in natural vision.
NIH EY08266 (MSL), James S. McDonnell Foundation (EG), Howard Hughes Medical Institute (EPS).