Journal Article

The uncrowded window of object recognition

Pelli, Denis G, Tillman, Katharine A

2008

Overview

This perspective article proposes a general law (Bouma law), which states that a visual object is crowded (and therefore cannot be perceived) when spacing between multiple objects is less than a critical spacing value. Crucially, this value is independent of the object. 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.

• Publisher: Nature Publishing Group US,Nature Publishing Group
• Subject: Animal Genetics and Genomics / Animals / Behavioral Sciences / Biological Techniques / Biomedical and Life Sciences / Biomedicine / Brain / Form perception / Form Perception - physiology / Humans / Models, Psychological / Neurobiology / Neurons / Neurosciences / Pattern Recognition, Visual - physiology / perspective / Physiological aspects / Psychophysics / Visual Fields - physiology