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Brady, Timothy

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Brady, Timothy

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2011 - 20152

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Author's Publications: search.filters.isAuthorOfPublication.04987d1d-5dc7-4100-8cd6-acc41adde2fd

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    Hierarchical Encoding in Visual Working Memory
    (SAGE Publications, 2011-02-04) Brady, Timothy; Alvarez, George
    Influential models of visual working memory treat each item to be stored as an independent unit and assume that there are no interactions between items. However, real-world displays have structure that provides higher-order constraints on the items to be remembered. Even a display with simple colored circles contains statistics, such as the mean circle size, that can be computed by observers to provide an overall summary of the display. We examined the influence of such an ensemble statistic on visual working memory. We report evidence that the remembered size of each individual item in a display is biased toward the mean size of the set of items in the same color and the mean size of all items in the display. This suggests that visual working memory is constructive, encoding displays at multiple levels of abstraction and integrating across these levels, rather than maintaining a veridical representation of each item independently.
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    Individual differences in ensemble perception reveal multiple, independent levels of ensemble representation.
    (American Psychological Association (APA), 2015-04) Haberman, Jason; Brady, Timothy; Alvarez, George
    Ensemble perception, including the ability to "see the average" from a group of items, operates in numerous feature domains (size, orientation, speed, facial expression, etc.). Although the ubiquity of ensemble representations is well established, the large-scale cognitive architecture of this process remains poorly defined. We address this using an individual differences approach. In a series of experiments, observers saw groups of objects and reported either a single item from the group or the average of the entire group. High-level ensemble representations (e.g., average facial expression) showed complete independence from low-level ensemble representations (e.g., average orientation). In contrast, low-level ensemble representations (e.g., orientation and color) were correlated with each other, but not with high-level ensemble representations (e.g., facial expression and person identity). These results suggest that there is not a single domain-general ensemble mechanism, and that the relationship among various ensemble representations depends on how proximal they are in representational space.