TR-A-0055 :1989.6.19

佐藤隆夫

ランダムドット・パターンの両眼分離・継時刺激における 運動知覚と奥行知覚

Abstract:It is known that apparent motion can not be perceived when two patterns of random-dot kinematograms are presented dichoptically, although classical apparent motion can be perceived under dichoptic and sequential(D-S) presentation (Braddick, 1974). These results suggest that D-S motion perception is dependent on dot-density. However, it is also known that stereoscopic perception is possible with D-S presentation when SOA is small (Ogle, 1963). The relationship between the two perception has not been clarified, since all past D-S studies examine either only motion or only depth. To clarify the relationship, relative frequency and accuracy of motion and depth perception were measured while varying dot-density (1-50%), SOA (15-240 ms, ISI=0, SOA=duration), and disparity (3- 48'). Two 6°x6° random-dot patterns (dot-size=3') with a central disparate square target and an identical background were used. Each pattern was presented only once. The subject's task was to say whether the target was in depth or in motion, and then to discriminate direction of depth(near/far) or motion (right/left). Depth perception was dominant at shorter SOAs(<100 ms), while motion perception became dominant at longer SOAs(>100 ms). Relative frequency of depth decreased, while that of motion increased as SOA was increased. At intermediate SOAs, depth perception was more frequent with high dot-densities, but motion was more frequent with low dot-densities, i.e. depth favors high, but motion favors low dot-density. As for accuracy, it was nearly 100% for depth in favorable conditions, but for motion, it was about 50% in most conditions. The perceived direction depended almost completely on eye-order, i.e. rightward motion was perceived when the first stimulus was presented to the right eye. Better motion-accuracies were obtained only with very low dot density, long SOA, and large displacement, i.e. conditions favorable for the classical motion. It is concluded that (1) Dichoptic information is fed primarily into the stereo system when SOA is short, and that (2) the short-range motion mechanism does not seem to functio under D-S presentation; motion perception under D-S presentation is either eye-order-dependent motion or classical apparent motion.