Feature binding in attentive tracking of distinct objects

To what degree can attentive tracking of objects' motion benefit from increased distinctiveness in the objects' surface features? To address this question, we asked observers to track 4 moving digits among a total of 8 moving digits. By varying the distinctiveness of the digits' color and identity, we found that tracking performance improved when the 8 objects were all distinct in color, digit identity, or both, compared to when the 8 objects were identical. However, when the 8 objects were distinct in a combination of color and digit but targets and nontargets shared color or digit identity, performance enhancement was not observed. Four follow-up experiments extended the range of the feature dimensions generating the effect and ruled out alternative strategic accounts. We conclude that surface features can be used to enhance tracking performance. This enhancement is feature-based, revealing a limited degree of feature binding in attentive tracking.