Continuous flash suppression operates in local spatial zones: effects of mask size and contrast

Abstract

Continuous flash suppression (CFS) is a technique in which presenting one eyewith a dynamic Mondrian sequence prevents a low-contrast target in the other eye frombeing perceived for many seconds. Frequently used to study unconscious visualprocessing, CFS bears many similarities with binocular rivalry (BR), another populardichoptic stimulation technique. It is therefore puzzling that the effect of mask size andcontrast seem to differ between CFS and BR. To resolve this discrepancy, we conducted asystematic investigation on the effects of mask size and contrast in CFS. Also, buildingon findings from BR, we asked if the collinearity of the contours in the Mondrian maskerplay a role in CFS suppression. Our results showed a robust effect of mask contrast onsuppression durations, and an effect of mask size that depended on collinearity.Specifically, higher mask contrasts produced longer suppression regardless of collinearityand mask size. Mask size, on the other hand, had little effect on suppression whencollinearity was low and it weakened suppression when collinearity is high. Theseobservations parallel prior findings in BR, further substantiating the close link betweenthe two paradigms and demonstrating the usefulness of a shared explanatory frameworkdescribing both phenomena.