Figure 6.

Test stimuli and expected results of Experiment 3. Two sets of stimuli with 1:1 (A,C) and 1:4 (B,D) motion direction differences, respectively. Examples of a balanced (A) and an unbalanced (B) stimulus. The center on the ambiguous figure was shown by the gray dashed line. Motion direction difference was equivalent to the length of border between black and white objects, which was shown by the red solid and dashed ellipses on (A,B). The red dashed ellipses presented the motion direction difference on the left side. The solid ellipses indicated the right side’s motion direction difference. The motion direction difference of the stimuli in (A,C) was balanced, so that the border lengths of the left [dashed ellipse in (A)] and right [solid ellipse in (A)] side with respect to the center were identical, whereas those in (B,D) were unbalanced {the border lengths were 1 and 4 in the left [dashed ellipses in (B)] and right [solid ellipses in (B)] sides, respectively}. (E) Illustration of the expected results. The left and right panels show the expected results for stimuli with balanced (Group 1:1) and unbalanced (Group 1:4) motion direction difference, respectively. If the motion direction difference underlay the modulation of DOF, participants would perceive a figure more frequently in the direction with more motion direction difference. In the example of Group 1:4, the right side included more motion direction difference than the left side; thus, participants would tend to observe white objects as a figure more frequently. The red and blue arrows indicate the modulations evoked by the difference in motion direction differences, and i to iv indicate the types of modulation. See text for details.