chronostasis

Chronostasis is a perceptional time illusion in which the first moment after a saccadic eye movement is perceived as lasting longer than it actually does. The most familiar example occurs when looking at a clock; the moment you fixate after a saccade, the clock's subsequent tick may seem to linger. The term derives from Greek chronos time and stasis standing.

Mechanism: The effect is attributed to the brain's attempt to maintain a stable percept of the world during rapid eye movements. During a saccade, visual processing is suppressed; immediately after, the brain concatenates pre-saccadic neural activity with the incoming post-saccadic input, effectively expanding the first post-saccadic interval. Memory and predictive timing also contribute.

Experimental evidence: Chronostasis has been demonstrated in experiments using clock faces and ticking sounds. After a saccade to a new fixation point on a clock, observers report that the immediate first interval appears longer by a fraction of a second. The magnitude is variable, typically on the order of hundreds of milliseconds, and can depend on attention and task demands.

Variants and scope: It is primarily a visual phenomenon and is most often discussed in the context of time perception and saccadic eye movements. It is not generally viewed as a pathological condition, though it is studied in neurological and perceptual research.

See also: time perception; saccadic suppression; stopped-clock illusion; perceptual continuity.