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Harry Haladjian, Zenon Pylyshyn, Allan Kugel; Multiple object tracking through temporal gaps created by the fading of objects. Journal of Vision 2009;9(8):246. doi: 10.1167/9.8.246.
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© ARVO (1962-2015); The Authors (2016-present)
In three experiments, we examined whether the encoding of object location is used in Multiple Object Tracking. Observers were asked to track four target discs among eight identical distractors on a display where the same random-dot texture was used for object surfaces and display background. Stereoscopic glasses were used to create two display conditions: 3D (where objects appeared to float in front of the background texture) and 2D (where objects appeared on the background texture). In the 2D displays, disks were only visible while they moved and became indistinguishable from the background when they stopped. In 75% of the trials, the objects halted movement mid-trial for one, two, or four seconds.
Experiment 1 used textured discs with no borders. During the pauses, the discs would appear to dissolve into the background in the 2D condition but remained distinct in the 3D condition. This produced significantly lower tracking performance only in the 2D trials with the longest pause; no decline was observed in the 3D condition.
Experiment 2 was identical to Experiment 1, except the discs had a white border during the entire trial, allowing the discs to remain distinct during the pauses. In this case there was no effect of pause duration.
Experiment 3 used the same 2D display as Experiment 1, except that in half of the trials object borders flashed “on” before halting. Here, there was an effect of pause duration in both flash and non-flash conditions (decreased performance with longer pauses).
These experiments found that objects that disappear without an abrupt offset are more difficult to track, indicating that object locations are not encoded and used to continue tracking after a gap in visibility. This suggests that the tracking mechanism does not encode location information unless cued by abrupt changes in the visual scene.
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