Direction information in multiple object tracking is limited by a graded resource.
Is multiple object tracking (MOT) limited by a fixed set of structures (slots), a limited but divisible resource, or both? Here, we answer this question by measuring the precision of the direction representation for tracked targets. The signature of a limited resource is a decrease in precision as the square root of the tracking load. The signature of fixed slots is a fixed precision. Hybrid models predict a rapid decrease to asymptotic precision. In two experiments, observers tracked moving disks and reported target motion direction by adjusting a probe arrow. We derived the precision of representation of correctly tracked targets using a mixture distribution analysis. Precision declined with target load according to the square-root law up to six targets. This finding is inconsistent with both pure and hybrid slot models. Instead, directional information in MOT appears to be limited by a continuously divisible resource.
Visual Attention Laboratory, Brigham and Women's Hospital, Boston, Massachusetts 02139, USA. toddh@search.bwh.harvard.edu
Todd S
TS
Horowitz
Michael A
MA
Cohen
D001288:Attention; D006801:Humans; D008960:Models, Psychological; D009039:Motion Perception; D009949:Orientation; D010364:Pattern Recognition, Visual; D011597:Psychomotor Performance; D013028:Space Perception