Cooperative phenomena in apparent movement perception of random-dot cinematograms

To determine if apparent movement perception of random-dot cinematograms (RDC) is a cooperative process, we examined the interaction between adjacent areas whose movement, when perceived independently, was in opposite directions. The stimulus contained alternating ambiguous and unambiguous horizontal random-dot stripes of equal width. The ambiguous areas were biased in a specific direction opposite to the movement of the unambiguous areas. The cooperative process was evaluated by noting that the unambiguous areas were able to reverse the perceived direction of the ambiguous areas. Thus all dots were seen to move uniformly in the unambiguous direction. This phenomenon was dependent on the amount of bias inserted in the ambiguous areas and the width of the stripes. A Cooperative Strength (CS) index was computed. We found that CS depended on the stripe width, and that the average cooperative neighborhood was about 15 min arc in visual angle, suggesting a relationship to the diameter of cortical hypercolumns.