Filling-in at the natural blind spot contributes to binocular rivalry.

The human natural blind spot is usually filled in based on the contextual information. When two sufficiently different images are presented to the two eyes, observers typically perceive an alternation between the two images (binocular rivalry). Both the filling-in process and binocular rivalry have been the subject of considerable research. This study investigates whether filled information in one eye's natural blind spot can contribute to binocular rivalry. A radial grating (D=12 degrees ) was presented to one eye, centered on the natural blind spot. Observers perceived a complete figure in monocular view; the blind spot area was filled-in based on the surrounding information. Simultaneously, a circular grating smaller than the blind spot (D=4 degrees ), was presented to the fellow eye in the region corresponding to the other eye's blind spot. The amount of rivalry as indexed by how often the smaller circular grating remained visible was measured. The results suggest that the filled information in the area of the blind spot does contribute to the rivalry process.