Abstract
Previous research on feature binding in visual working memory has supported a privileged role for location in binding together non-spatial features of an object, such as shape and color. However, humans are able to correctly recall feature conjunctions of objects that occupy the same location at different times. In a series of behavioral experiments, we investigated binding errors under these conditions. In particular, we tested the hypothesis that sequential position can take the role of location in mediating feature binding.
In two experiments, participants viewed three colored shapes presented sequentially at the screen center. They were then cued with either a visual feature of one of the objects or a number indicating its position in the sequence, and had to report the remaining object properties. We found that report errors for color and shape were largely uncorrelated when participants were cued with an item's sequential position. However, when participants were cued with e.g. an item's shape and reported an incorrect sequential position, they had a high chance of also making the corresponding error in reporting the item's color. These patterns of binding errors across conditions matched the predictions of a model in which binding between color and shape is mediated by the binding of each individual feature to an object's sequential position.
In a third experiment, we directly compared the roles of location and sequential position in feature binding under conditions where both are available. Participants viewed a sequence of colored disks displayed at different locations, and were cued either by a disk's location or its sequential position to report its remaining properties. The pattern of errors supported a mixed strategy with individual variation, suggesting that binding via either time or space could be used for this task.