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Kristy vanMarle, Brian J Scholl; Attentive tracking of objects vs. substances. Journal of Vision 2003;3(9):586. doi: 10.1167/3.9.586.
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© 2015 Association for Research in Vision and Ophthalmology.
Recent research in vision science, infant cognition, and word-learning all suggest a special role for the processing of individual discrete objects. But what counts as an object? Answers to this question often depend on contrasting object-based processing with the processing of spatial areas, or unbound visual features. In infant cognition and word-learning, though, another salient contrast has been between rigid cohesive objects and nonsolid substances. Whereas objects may move from one location to another, a nonsolid substance must *pour* from one location to another. Here we explore whether attentive tracking processes are sensitive to dynamic information of this type. We employ the multiple-object tracking task, wherein observers are presented with an array of identical items, a subset are briefly highlighted as targets, and observers must use attention to keep track of the targets as all of the items move randomly about the display — so that they can indicate the targets at the end of a 20-second tracking period. We find that observers can easily track 4 in 8 identical unpredictably-moving items which move as discrete objects from one location to another, but cannot track similar entities which noncohesively ‘pour’ from one location to another — even when the items in both conditions follow the same trajectories at the same speeds. Other conditions reveal that the inability to track multiple ‘substances’ stems not from the violations of rigidity or cohesiveness per se, since subjects are able to track multiple non-cohesive collections and multiple non-rigid deforming objects. Rather, the impairment is due to the dynamic extension and contraction during the ‘substance-like’ motion, which render ‘the’ location of the entity ambiguous. We will demonstrate these and other effects, which suggest a convergence between processes of mid-level adult vision and infant cognition, and in general help to clarify what can count as a persisting dynamic ‘object’ of attention.
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