Segregating targets and nontargets in depth eliminates inhibition of nontargets in multiple object tracking

Multiple Object Tracking (MOT) is a useful paradigm for studying properties of visual attention. In a typical MOT task, eight or more identical objects are presented on a computer screen. Several of these objects are distinguished as targets by flashing briefly at the beginning of a trial. These objects then move in a random and unpredictable manner, and the observer is asked to identify the targets at the conclusion of this movement (as described in Pylyshyn, 2001; Pylyshyn & Storm, 1988). Observers can easily track four or five objects among identical distractors in a varying range of conditions. Such results have been interpreted as the function of visual indexes (also called FINSTs), which are the preattentive individuation mechanisms proposed by Visual Indexing Theory (Pylyshyn, 2001).