Differential target enhancement, not reactive inhibition determines levels of guidability in Multiple Object Tracking

Flexible resource models suggest that attentional deployment in Multiple Object Tracking (MOT) either shows in target enhancement or distractor inhibition or both. In order to gauge the influence of these processes we manipulated distinctiveness of targets and distractors along a single dimension by finely grading gray values of objects. We established that a quantitative increase in distinctiveness results in a quantitative increase in tracking performance thus demonstrating a new finding. Further increases of distinctiveness beyond a certain degree produced no further improvements in tracking. This effect, however, was moderated by levels of load thus providing evidence for the relativity of this effect. With higher task loads higher degrees of distinctiveness still resulted in a significant performance gain (Experiment 1). A follow up experiment generalized this finding. By manipulating speed of objects, a yet higher load situation could be established showing that an increase of an already striking distinctiveness can produce an even further performance gain - provided that task load is very high (Experiment 2). Finally we tested the hypothesis that target enhancement and distractor inhibition are influenced by feature distinctiveness. Although we found possible indications for distractor inhibition, we could not demonstrate an effect of feature distinctiveness on distractor inhibition. Target enhancement, however, was substantially influenced by variation of feature distinctiveness (Experiment 3).