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Susan Carrigan, Philip Kellman; Differentiating Local and Global Processes in Amodal Completion: Dot Localization with Familiar Logos. Journal of Vision 2016;16(12):310. doi: https://doi.org/10.1167/16.12.310.
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© ARVO (1962-2015); The Authors (2016-present)
Previously, we reported evidence that competing global and local theories of amodal completion may reflect two different processes: a relatively local perceptual process that completes contours according to local geometry and produces precise boundary representations, and a more global recognition process that suggests likely shape based symmetry or familiarity but does not produce precise boundary representations. These two processes were distinguished experimentally via a dot localization procedure. Here, we applied the same method to test familiarity in amodal completion using familiar logos. Participants were assigned to either a local or a global condition, which determined how the participant was instructed to complete occluded logos. Global participants were instructed to complete the logo according to its familiar shape. Local participants were instructed to ignore the familiarity of the logo and instead complete the shape with a smooth contour according to the relatability of edges and endpoints. On each trial, an occluded logo was presented, and a small red dot was flashed on top of the occluder. Subjects made a forced choice of whether the dot fell inside or outside of the interpolated boundary. Interleaved adaptive 2-up, 1-down staircases were used to estimate two points on the psychometric function: the .707 probability that the dot was seen as outside of the occluded object's boundaries (outer threshold), and the .707 probability that the dot was seen as inside the occluded object's boundaries (inner threshold). We examined imprecision, measured as the distance between these two thresholds, location, measured as the mean of these two thresholds, and location error, measured as the absolute value of location. Consistent with earlier results regarding symmetry, the results reveal that, while local completion consistently produces precise and accurate boundary representations, global completion does not.
Meeting abstract presented at VSS 2016
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