Figure 2. A schematic representation of the stimuli used. Only one panel was presented to each eye. When uncross-fused, the right-hand pair represents the stimuli used in experiment 1, the left-hand pair experiment 2. In order not to show the edges of the background and the edges of the monitor, the area between the inducers (the 'mortar') was made as black as possible (0.2 cd m-2), although in this figure this area is printed in medium gray because on paper the dark inducers do not separate from the black mortar.