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Zenon W Pylyshyn, Carly Leonard; Inhibition of nontargets during multiple object tracking (MOT). Journal of Vision 2003;3(9):585. doi: 10.1167/3.9.585.
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© ARVO (1962-2015); The Authors (2016-present)
In Multiple Object Tracking (MOT), observers keep track of a set of (about 4) targets which move randomly and independently among a set of identical nontargets. Earlier we reported that keeping track of the identity of targets (as measured by recall of their previously assigned labels) tended to be poorer that keeping track of their status as targets, and that ID errors tended to increase more rapidly with trial length. We provided evidence that this was likely due to the fact that targets tended to be more frequently confused with other targets than with nontargets.
A possible reason for this asymmetry is that nontargets might be actively inhibited in MOT, thus resulting in their being less readily confused with targets. In the present study we investigated this hypothesis using the dot-probe method first adopted by (Watson & Humphreys, 1997). Observers viewed an MOT display during which they had to detect the brief appearance of a small spot that occurred on 50% of the trials at one of 3 location types: on a target, a nontarget, or somewhere in between. At the end of each trial, observers selected the targets using a mouse, and then indicated whether or not there had been a probe during that trial.
We found that accuracy for detecting a probe was significantly worse when the probe was on a nontarget. No other pairwise contrast was statistically reliable. Tracking performance also appeared to be the same for all probe locations as well as for the no-probe condition.
These results are consistent with the hypothesis that nontargets are inhibited during MOT, thus accounting for the asymmetry between target-nontarget and target-target confusions. They are also consistent with the hypothesis that MOT does not consume the same visual-attention resources as monitoring a visual event. These results are discussed in relation to the FINST Visual Indexing Hypothesis.
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