Real-world objects are not stored in bound representations in visual working memory
When storing multiple objects in visual working memory, observers sometimes misattribute perceived features to incorrect locations or objects. These "swaps" are usually explained by a failure to store object representations in a bound form. Swap errors have been demonstrated mostly in simple objects whose features (color, orientation, shape) 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 1, observers were simultaneously shown four items from two object categories (two exemplars per category). Within a category, the exemplars could be presented in either the same (two open boxes) or different states (one open, one closed box). 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. Participants showed good memory for exemplars when no binding was required. However, when the tested objects were shown in the different states, participants were less accurate. Good memory for state information and for 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 even for real-world objects. In Experiment 2 we used the same tasks, but on half of trials the locations of the exemplars were swapped at test. We found that participants ascribed incorrect states to exemplars more frequently when the locations were swapped. We conclude 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.