Demand-based dynamic distribution of attention and monitoring of velocities during multiple-object tracking.

The ability to track multiple moving objects with attention has been the focus of much research. However, the literature is relatively inconclusive regarding two key aspects of this ability, (1) whether the distribution of attention among the tracked targets is fixed during a period of tracking or is dynamically adjusted, and (2) whether motion information (direction and/or speed) is used to anticipate target locations even when velocities constantly change due to inter-object collisions. These questions were addressed by analyzing target-localization errors. Targets in crowded situations (i.e., those in danger of being lost) were localized more precisely than were uncrowded targets. Furthermore, the response vector (pointing from the target location to the reported location) was tuned to the direction of target motion, and observers with stronger direction tuning localized targets more precisely. Overall, our results provide evidence that multiple-object tracking mechanisms dynamically adjust the spatial distribution of attention in a demand-based manner (allocating more resources to targets in crowded situations) and utilize motion information (especially direction information) to anticipate target locations.