Academic journal article Attention, Perception and Psychophysics

The Locus of Crowding Effects

Academic journal article Attention, Perception and Psychophysics

The Locus of Crowding Effects

Article excerpt

VISUAL PROCESSING

CHAKRAVARTHI & CAVANAGH (2009). Recovery of a crowded object by masking the flankers: Determining the locus of feature integration. J Vis, 9(10), Art. 4.

Where in the brain, in the course of visual processing, are local features put together in a manner that permits object recognition? One might expect that question to frame a story about the latest fMRI localization study. However, Chakravarthi and Cavanagh remind us that there are elegant behavioral/psychoanatomical methods for addressing such issues. In their experiment, observers tried to identify the orientation of a C-like figure surrounded by four other similar figures. These flanking Cs produced a "crowding" effect. When the flankers were present, an otherwise identifiable C became unidentifiable. Crowding is thought to occur when features from the flankers get pooled with features from the target, disrupting target identification. Chakravarthi and Cavanagh used several masking methods to attempt to kill off the features of the flankers before they have a chance to interfere with the central object. If crowding stimuli are followed by a superimposed noise pattern, the identification of those stimuli can be brought to near-chance levels. …

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