Method at a glance
- Modality: visual (peripheral vision)
- Measures: The accuracy of identifying a peripheral target flanked by nearby distractors — a limit on object recognition in cluttered peripheral vision
- Procedure: While the observer fixates centrally, a peripheral target (e.g. a letter) is surrounded by an array of similar flankers. The flankers impair identification of the target (‘crowding’); discrimination accuracy (typically a forced-choice on target identity) is the dependent measure. Because it is an accuracy task, crowding does not depend on reaction time or interocular competition.
- Also called: crowding, visual crowding paradigm
Strengths
- Accuracy-based, so it avoids the reaction-time and time-to-emergence confounds that dog masking and breaking-CFS measures.
- Does not rely on binocular rivalry / interocular suppression, so it provides a mechanistically independent test of an effect first found with CFS.
Limitations
- A peripheral-vision phenomenon under constant fixation; requires eye-movement control and careful placement of target/flanker eccentricity and spacing.
- Taps a different (peripheral resolution / object-recognition) limit than CFS, so convergence across the two is informative but they are not measuring the same construct.
Connections
- Key studies: Salomon et al. (2016)
- Related methods: Continuous flash suppression
A limit on peripheral vision: a target that is easily identified in isolation becomes hard to recognize when flanked by nearby similar items, even though it remains visible. Crowding is a failure of object recognition, not of detection — the observer sees that something is there but cannot identify it — and it is indexed by discrimination accuracy in a forced-choice task (e.g. “which way does the target letter point?”).
Why the wiki holds it
Its value here is as a converging, artefact-free test. Breaking-CFS uses reaction-time-like time-to-emergence and depends on interocular competition, both of which have been criticized as confounds. Crowding shares neither: it is an accuracy measure with no rivalry component. So when Salomon et al. (2016) found that visual targets flashed synchronously with the viewer’s own heartbeat were discriminated less accurately under crowding (56% vs 69%), reproducing the cardio-visual suppression they had found with CFS, it ruled out an explanation specific to the breaking-CFS paradigm — the suppression is a general property of cardiac-synchronous vision, not an artefact of one task.