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Elias H Cohen, Elan Barenholtz, Manish Singh, Jacob Feldman; Superior change detection at shape concavities. Journal of Vision 2003;3(9):270. doi: 10.1167/3.9.270.
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© ARVO (1962-2015); The Authors (2016-present)
Shape representation was studied using a change detection task. Observers viewed two individual shapes in succession, either identical or one a slightly altered version of the other, and reported whether they detected a change. We found a dramatic advantage for changes involving shape concavities compared to those involving convexities of equal magnitude. In Experiment 1, observers were more accurate when a concavity along the contour was introduced, or removed, compared to a convexity. Experiment 2 showed the same detection asymmetry for changes involving a simple modification of an existing concave or convex vertex. In both experiments, a large difference in sensitivity for contour type (reported in d') was observed across both directions of change (addition or deletion of shape area) as well as across all change magnitudes studied. This result sheds light on the underlying representation of visual shape, and in particular the central role played by part boundaries. Moreover, this finding shows how change detection methodology can serve as a useful tool in studying the specific form of visual representations.
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