Figure 4.

(Top) Stimuli used in Experiment III dual-motion detection tasks. A total of four frames is presented. Two distractor annuli are placed in between the inner and outer annuli to avoid the perception that the two annuli always seem to rotate in the same directions. The inner and outer radii of the inner annulus are 0.8° and 1.6°, respectively, and those of the outer annulus are 4.0° and 5.0°, respectively. (Middle) AOC graphs for group A observers. The abscissa and the ordinate represent heterogeneous direction of motion perception for inner and outer annuli, respectively. (Bottom) AOC graphs for group B observers. Axes represent perception of the homogeneous motion direction of outer and inner annuli. Data for dual-task performance lie in a concave area under the diagonal line. AOC graphs of two observers from each group are shown: group A: AW and CE; group B: DB and MS. Two other observers for each group showed similar behavior.