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Julian M. Wallace, Bosco S. Tjan; Object Crowding. Journal of Vision 2010;10(7):1334. doi: 10.1167/10.7.1334.
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© ARVO (1962-2015); The Authors (2016-present)
Crowding occurs when stimuli in the peripheral field become harder to identify when flanked by other items within a spatial extent that depends on eccentricity (Korte, 1923; Bouma, 1970). Crowding has been demonstrated extensively with simple stimuli such as gabors and letters. Here we characterize crowding for everyday objects. We presented three-item arrays of objects and of letters, arranged radially and tangentially in the lower visual field. Observers identified the center object, and we measured contrast energy thresholds as a function of target-to-flanker spacing (center-to-center). We found that object crowding is similar to letter crowding in spatial extent, but is much weaker (∼2.5x vs. ∼11x in threshold elevation relative to an unflanked target). We also examined whether the exterior and interior features of an object, operationally defined, are differentially affected by crowding. We used a circular aperture to present either just the interior portion of an object or everything else but the interior (a ‘donut’ object). For both apertures and donuts, critical spacing and threshold elevation were similar to those of intact objects. To sum up, crowding between objects does not significantly differ from that between letters in terms of spatial extent and the anisotropy along the radial and tangential directions. However, crowding-induced threshold elevations for objects (intact, aperture, donut) are much lower than that for letters. Taken together, these findings suggest that crowding between letters and objects are essentially due to the same mechanism, which affects equally the interior and exterior features of an object. However, for objects, it is easier to compensate for the loss in performance by increasing contrast.
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