Abstract
Several activities such as driving or video-gaming require the ability to track several objects simultaneously. This ability is studied in the multiple object tracking paradigm (MOT). Observers track targets among identical distractors. Previous research suggests that distractors are inhibited during MOT by narrowing the attention foci on targets to compensate decreasing target-distractor distances. In four experiments, we tested whether the sizes of the attention foci are dependent solely on inter-object spacing and thus symmetrical around targets or whether they omit distractor locations. During brief flashes, we displaced each distractor on a circular path around its associated target object thus maintaining inter-object spacing. Distractor displacements would not impair tracking performance if the attention foci were symmetrical around targets whereas displacements would decrease performance if the attention foci were asymmetric around targets. In Experiment 1a, we observed impaired tracking performance when distractors were displaced during tracking. Changing movement directions of distractors improved performance. Experiment 1b revealed direction changes of distractors to increase performance only when they are unique for distractors, whereas target direction changes impaired tracking in general. Furthermore, we tested whether changes in the global (Experiment 2) or local configuration (Experiment 3) of objects can account for the effect of distractor displacements. In Experiment 2, we varied the number of displaced distractors. We observed tracking performance declining linearly. In Experiment 3, we controlled for local configuration changes. During each trial, three distractors were displaced by 50°, 100°, or 150° around their associated target. One distractor was not displaced. Tracking was less accurate with larger displacements. However, for 50° displacements performance was equal to no displacements. We conclude that the attention foci omit distractor positions and that attention is not symmetrically distributed around targets. We argue in favor of a flexible resource model deploying attention asymmetrically among and around tracked targets.
HSM was supported by a scholarship of the Leibniz Graduate School for Knowlegde Media Research. MH and GJ were supported by German Research Foundation (DFG) Grants HU 1510/4-1 and JA 1761/5-1.