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Edward Vogel, Andrew McCollough, Trafton Drew, Todd Horowitz; Probing the distribution of attention to targets and distractors in multiple object tracking. Journal of Vision 2010;10(7):245. doi: https://doi.org/10.1167/10.7.245.
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© ARVO (1962-2015); The Authors (2016-present)
How is attention allocated during multiple object tracking (MOT)? In previous research, we have demonstrated a significant enhancement of the anterior N1 component (150ms post-stimulus) for task-irrelevant probes on targets relative to distractors (Drew et al. 2009). We argued that this reflects attentional enhancement for targets during MOT. Here we use this ERP component to study how attentional allocation responds to various tracking challenges. In Experiment 1, observers tracked 2 targets among 2, 4, or 6 distractors. The anterior N1 amplitude to targets increased relative to distractors as distractor load increased. In Experiment 2, observers tracked 2, 3, or 4 targets among 6 distractors. Here the target-distractor amplitude difference decreased as target load increased. Note that both of these manipulations vary the density of the display, yet the attentional system responds differently depending on whether additional items are targets or distractors. Increased distractor load leads to increased attentional focus on targets, while increased target load tends to reduce this focus. We suggest that the first effect reflects a strategic decision to increase the attentional allocation to targets faced with greater threat from distractors. In contrast, the second effect presumably reflects failures of attention as attention is spread more thinly across targets. These results suggest that during multiple object tracking attention is focused more tightly on targets as spacing decreases, but this strategy is inhibited by increased target load. Thus the attentional system responds flexibly and intelligently to protect targets from distractor interference.
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