Fig. 1.

Illustration of the three masking conditions in Experiment 1 (a; closed-curvature stimuli) and in Experiment 2 (b; open-curvature stimuli). Stimuli were presented to the left eye (L; not illustrated here), the right eye (R), or both eyes, depending on condition. In the no-mask condition, the adaptor was presented to one eye (with no mask) and was nearly always clearly visible. In the monoptic-mask condition, the adaptor was presented to one eye, and the mask was superimposed over the adaptor in the same eye; both mask and adaptor were nearly always clearly visible. In the dichoptic-mask condition, the adaptor and mask were presented to different eyes; in almost all cases, only the mask was visible.