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Mutsumi Suganuma, Kazuhiko Yokosawa; Effect of entrained motion of items on MOT task. Journal of Vision 2004;4(8):369. doi: https://doi.org/10.1167/4.8.369.
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© ARVO (1962-2015); The Authors (2016-present)
Based on a multiple object tracking (MOT) paradigm, we demonstrated that observers ability to track targets were disrupted when items chased each other (Suganuma & Yokosawa, 2002; VSS). This result suggested that they were made in a group, and might be treated as a single object as a whole. However, it is still unclear of what information caused such grouping on a ‘chasing’ MOT task. Because in a chasing display, paired items were entrained in two ways. That is, items moved straight in the same direction (same vector), and, they shared their trajectory (spatial location). In present study, we examined the effect of such entrained motion of the items in extent. In particular, we examined whether the same vector or sharing of the trajectory, was the critical factor of impairment of tracking ability in chasing MOT. In our experiments, five target and five distractor items were presented. The movement sequence was presented for 14 seconds. In the first experiment, we compared the tracking performance between control (ordinary MOT), chase, and same vector conditions. In the same vector condition, paired items moved in the same direction, however they did not shared their trajectory. The performance for the same vector condition was almost the same as chase condition, which was significantly lower than that for control condition. In the second experiment, we examined the effect of sharing same trajectory. In random path condition, one item chased another item. However, in contrast to the chase condition, those items moved in randomly changing direction and velocity. As a result, performance for random path condition was equally disrupted as chase condition, which was significantly lower than the control condition. These results show that if two items moved in entrainment, they are treated as one group of items. Based on these results, we discuss what attribute of the ‘item’ is tracked in MOT task.
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