Figure 1

Stimuli used in the experiment. (a) The DoG bars had a white center surrounded by a darker grey region on both sides. A white square outline served as the binocular fusion lock. Two fine vertical black lines pointing towards the center part of the reference served as a fixation guide. The horizontal reference bar was presented continuously to one eye. The two vertical suppressors were presented briefly (1 s) to the other eye following a keypress. (b) Subjects adjusted the separation of the vertical bars to the widest setting that still suppressed the horizontal segment between them, and could present the suppressors as many times as needed. The distance between the center of the two suppressors is termed as the suppression zone width, (red arrow). An illustration of the area of perceived suppression upon vertical suppressor appearance is outlined by the yellow circles. (c–e) These figures illustrate the different combinations of contrast polarity tested in Experiment 2B: (c) black–black, (d) black–white, and (e) white–black. The first color in the combination refers to the center of the horizontal reference followed by the vertical suppressors.