TY - JOUR
T1 - Substitution and pooling in crowding
AU - Freeman, Jeremy
AU - Chakravarthi, Ramakrishna
AU - Pelli, Denis G.
N1 - Funding Information:
Thanks to Christoph Berendes (focus on substitution), Ronald van den Berg, Patrick Cavanagh (similarity proof), Frans Cornelissen, Kevin Larson (central vs. peripheral), Tomer Livne (absent letter reports), Josh McDermott (abstract), Michael Morgan (challenged the logic of our VSS talk), Charles Peskin (unfamiliar approach), Jay Rosen ( http://www.hyperorg.com/blogger/2009/07/19/transparency-is-the-new-objectivity/ ), Sarah Rosen (abstract), Josh Solomon (abstract, similarity proof), Katharine Tillman (entire text), and Jonathan Victor for helpful comments. Thanks to the anonymous reviewer who provided the clever alternative account of Experiment 1. Versions of this story were presented as talks at the Vision Science Society meeting in Naples, FL (May, 2010), and at the Biomath meeting of the NYU Courant Institute of Mathematics in New York, NY (March, 2011). Supported by a U.S. NSF Graduate Student Fellowship to J.F. and US NIH Grant R01-EY04432 to D.G.P.
PY - 2012/2
Y1 - 2012/2
N2 - Unless we fixate directly on it, it is hard to see an object among other objects. This breakdown in object recognition, called crowding, severely limits peripheral vision. The effect is more severe when objects are more similar. When observers mistake the identity of a target among flanker objects, they often report a flanker. Many have taken these flanker reports as evidence of internal substitution of the target by a flanker. Here, we ask observers to identify a target letter presented in between one similar and one dissimilar flanker letter. Simple substitution takes in only one letter, which is often the target but, by unwitting mistake, is sometimes a flanker. The opposite of substitution is pooling, which takes in more than one letter. Having taken only one letter, the substitution process knows only its identity, not its similarity to the target. Thus, it must report similar and dissimilar flankers equally often. Contrary to this prediction, the similar flanker is reported much more often than the dissimilar flanker, showing that rampant flanker substitution cannot account for most flanker reports. Mixture modeling shows that simple substitution can account for, at most, about half the trials. Pooling and nonpooling (simple substitution) together include all possible models of crowding. When observers are asked to identify a crowded object, at least half of their reports are pooled, based on a combination of information from target and flankers, rather than being based on a single letter.
AB - Unless we fixate directly on it, it is hard to see an object among other objects. This breakdown in object recognition, called crowding, severely limits peripheral vision. The effect is more severe when objects are more similar. When observers mistake the identity of a target among flanker objects, they often report a flanker. Many have taken these flanker reports as evidence of internal substitution of the target by a flanker. Here, we ask observers to identify a target letter presented in between one similar and one dissimilar flanker letter. Simple substitution takes in only one letter, which is often the target but, by unwitting mistake, is sometimes a flanker. The opposite of substitution is pooling, which takes in more than one letter. Having taken only one letter, the substitution process knows only its identity, not its similarity to the target. Thus, it must report similar and dissimilar flankers equally often. Contrary to this prediction, the similar flanker is reported much more often than the dissimilar flanker, showing that rampant flanker substitution cannot account for most flanker reports. Mixture modeling shows that simple substitution can account for, at most, about half the trials. Pooling and nonpooling (simple substitution) together include all possible models of crowding. When observers are asked to identify a crowded object, at least half of their reports are pooled, based on a combination of information from target and flankers, rather than being based on a single letter.
KW - Crowding
KW - Mixture modeling
KW - Pooling
KW - Substitution
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U2 - 10.3758/s13414-011-0229-0
DO - 10.3758/s13414-011-0229-0
M3 - Article
C2 - 22160819
AN - SCOPUS:84857564580
SN - 1943-3921
VL - 74
SP - 379
EP - 396
JO - Attention, Perception, and Psychophysics
JF - Attention, Perception, and Psychophysics
IS - 2
ER -