Unit of attentional refreshing in multiple identity tracking: object and Boolean map

Tracking multiple distinct moving objects requires periodically refreshing the objects' identity-location bindings. Classic theories assume that individual objects are the units involved in refreshing. Considering that features and locations can be represented as Boolean maps, here we investigated whether Boolean maps can also serve as the units of refreshing in multiple identity tracking (MIT). We used an adapted MIT paradigm, in which every two targets shared the same identity and thus could be represented in one Boolean map. We examined whether only the cued target was refreshed (i.e., object-based refreshing) or the other target sharing the same identity was also refreshed (i.e., Boolean map-based refreshing). In Experiment 1, where objects moved randomly, results showed that while the cued target was tracked better than uncued targets, no significant advantage was observed for the same-identity target, indicating no Boolean map-based refreshing. In Experiment 2, same-identity targets moved in parallel, maintaining a stable spatial relationship within each Boolean map. Both same-identity and cued targets were tracked better than other targets, demonstrating a same-Boolean-map advantage. In Experiment 3, where different-identities targets moved in parallel, no significant advantage was found for either the target moved parallel to or sharing the same identity as the cued target. Taken together, the results indicate that a Boolean map can serve as the unit for attentional refreshing in MIT, but only when targets with the same identity are moving in parallel, so that the spatial relationship within each Boolean map remains the same while the objects are moving; otherwise the refreshing is based on individual objects.