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 four moving digits among a total of eight moving digits. By varying the distinctiveness of the digits' colour and identity, we found that tracking performance improved when the eight objects were all distinct in colour, digit identity, or both, compared to when the eight objects were identical. However, when the eight objects were distinct in a combination of colour and digit but targets and nontargets shared colour 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.