The role of transient attention in crowding and feature binding

Crowding refers to the failure to identify a peripheral object due to nearby objects (flankers). A hallmark of crowding is the inner-outer asymmetry, i.e., the outer flanker (more peripheral) produces stronger interference than the inner one. Here, by manipulating attention, we tested the predictions of two competing accounts: the attentional account, which predicts a positive attentional effect on the asymmetry (i.e., attention to the outer flanker will increase the asymmetry), and the receptive field size account, which predicts a negative attentional effect. In Experiment 1, observers estimated a Gabor target orientation. A peripheral pre-cue draws attention to one of three locations: target, inner or outer flanker. Probabilistic mixture modeling demonstrated the asymmetry by showing that observers often misreported the outer flanker orientation as the target. Interestingly, the outer cue led to a higher misreport rate of the outer flanker, and the inner cue led to a lower misreport rate of the outer flanker. Experiment 2 tested the effect of asymmetry and attention on binding errors (e.g., reporting the tilt of one presented item with the color of another item). Observers reported both the tilt and color of the target. Attention increased target reports in both dimensions and led to a decrease in target binding. However, attention did not lead to a decrease in flanker biding errors. The results are consistent with the attentional account of crowding and suggest that the locus of spatial attention plays an essential role in crowding and the inner-outer asymmetry.

Real-world objects are not stored in holistic representations in visual working memory

When storing multiple objects in visual working memory, observers sometimes misattribute perceived features to incorrect locations or objects. These misattributions are called binding errors (or swaps) and have been previously demonstrated mostly in simple objects whose features are easy to encode independently and arbitrarily chosen, like colors and orientations. Here, we tested whether similar swaps can occur with real-world objects, where the connection between features is meaningful rather than arbitrary. In Experiments 1 and 2, observers were simultaneously shown four items from two object categories. Within a category, the two exemplars could be presented in either the same or different states (e.g., open/closed; full/empty). After a delay, both exemplars from one of the categories were probed, and participants had to recognize which exemplar went with which state. We found good memory for state information and exemplar information on their own, but a significant memory decrement for exemplar-state combinations, suggesting that binding was difficult for observers and “swap” errors occurred even for meaningful real-world objects. In Experiment 3, we used the same tasks, but on half of the trials, the locations of the exemplars were swapped at test. We found that participants ascribed incorrect states to exemplars more frequently when the locations of exemplars were swapped. We concluded that the internal features of real-world objects are not perfectly bound in working memory, and location updates impair the object representation. Overall, we provide evidence that even real-world objects are not stored in an entirely unitized format in working memory.