Binding Errors in Visual Working Memory for Real-World Objects

When storing multiple objects in visual working memory, observers sometimes misattribute perceived features to incorrect locations or objects. These called binding errors (or swaps) and have been demonstrated mostly in simple objects whose features are easy to encode independently. Here, we tested whether similar swaps can occur with real-world objects where the connections between features are meaningful. In Experiment 1A and B, observers were simultaneously shown four items from two object categories. Within a category, the exemplars could be presented in either the same or different states. After a delay, two exemplars drawn from one category were shown in both possible states. Participants had to recognize which exemplar went with which state. In a control task, they had to recognize two old vs. two new exemplars. Good memory for state information and exemplar information on their own, with a significant memory decrement for exemplar-state combinations, suggest that binding was difficult for observers and “swap” errors occurred for real-world objects. In Experiment 2A and B we used the same tasks, but on half of the trials, the locations of the exemplars (2A) or states (2B) were swapped at test. We found that participants make more errors when the locations of exemplars or states were swapped. We conclude that that the internal features of real-world objects are not perfectly bound in VWM and can be attached to locations independently. Overall, we provide evidence that even real-world objects are not stored in an entirely bound representation in working memory.