2次運動情報処理の非並列性

抄録

To investigate the possible difference between first-order (luminance defined) and second-order (contrast defined) motion processing, performance of visual search was examined for both types of motion by measuring the search time. The target was a patch that was drifting in a pre-determined direction, and the distractors were other patches that were drifting in the opposite direction. We found that the search could be performed in parallel for first-order motion, as expected from earlier studies, but not for second-order motion. For second-order motion, the search time increased as the number of distractors increased, with slopes of more than 400ms per item. These results indicate distinct processing schemes for first- and second-order motion. First-order motion should be processed through low-level filtering mechanisms that are spread over the visual field for parallel operation, as discussed in earlier studies. On the other hand, the present results suggest that the spatial distribution, detection scheme, or the later grouping operation is different for second-order motion, so that the search requires focal attention.