Perspective abstract

Nature Neuroscience , 1129 - 1135 (2008)
Published online: 25 September 2008 | Corrected online: 13 November 2008 | doi:10.1038/nn.2187

There is an Erratum (December 2008) associated with this Perspective

The uncrowded window of object recognition

Denis G Pelli1 & Katharine A Tillman1

It is now emerging that vision is usually limited by object spacing rather than size. The visual system recognizes an object by detecting and then combining its features. 'Crowding' occurs when objects are too close together and features from several objects are combined into a jumbled percept. Here, we review the explosion of studies on crowding—in grating discrimination, letter and face recognition, visual search, selective attention, and reading—and find a universal principle, the Bouma law. The critical spacing required to prevent crowding is equal for all objects, although the effect is weaker between dissimilar objects. Furthermore, critical spacing at the cortex is independent of object position, and critical spacing at the visual field is proportional to object distance from fixation. The region where object spacing exceeds critical spacing is the 'uncrowded window'. Observers cannot recognize objects outside of this window and its size limits the speed of reading and search.

  1. Department of Psychology and Center for Neural Science, New York University, 6 Washington Place, New York, New York 10003, USA.

Correspondence to: Denis G Pelli1 e-mail:

* In the version of this article initially published, the legend to Figure 5 contained several errors. The second sentence should read "Fixating on the red minus, you will be unable to identify the middle object in the first eight rows unless you isolate it by hiding the flanking objects with your fingers (or two pencils). " The fourth sentence should read "Grating patches, similar to those in the top row, are often taken to be one-feature objects. " These errors have been corrected in the HTML and PDF versions of the article.


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