Abstract
Unexpected changes in object trajectory can attract attention (Howard & Holcombe, 2010) and, increasing the number of changes in target trajectories during a multiple object-tracking (MOT) task negatively influences tracking accuracy (Ericson & Beck, OPAM 2011). Therefore, attention may be preferentially allocated to items that have recently changed trajectory and away from other items that could subsequently also change trajectory. It follows that MOT performance is poorer with more changes because attention is less likely to be available for allocation for every change in trajectory. We tested this possibility by incorporating a probe detection task immediately after a target abruptly changed direction. Using a rotational tracking design, four target-distractor pairs rotated independently of each other and each pair abruptly changed trajectory during the motion sequence either one or six times. During each trial, one probe appeared on a target. The probe always appeared immediately after a target changed trajectory. Probes were presented for 250 ms and appeared on the target that had just changed trajectory or one of the other targets. Participants were instructed to track the four targets and press a button each time a probe appeared. Replicating our changes in trajectory effect; when the probe was accurately detected, MOT performance was higher in the one-change condition than the six-change condition. Overall probe detection was higher for trials with six trajectory changes. Importantly, on accurate probe detection trials, reaction times were faster for the one-change trials compared to the six-change trials when the probe was on the same item, suggesting that attention was not allocated to the change item at the time the probe appeared in the six-change condition. These results suggest that although attention may be distributed across all target objects in a MOT task, attention may also be allocated preferentially to one item depending on task demands.
Meeting abstract presented at VSS 2013