Kappa effect

The kappa effect is a temporal illusion in which intervals between successive stimuli seem longer when the stimuli are farther apart in space.

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Tau effect: The tau effect is a spatial illusion in which the perceived distance between successive stimuli depends on the time separating them. It reverses the kappa effect’s relationship: timing alters perceived spatial distance.
Temporal interval: A temporal interval is the duration separating two events. The kappa effect concerns how this duration is perceived between successive stimuli.
Three-flash experiment: A three-flash experiment presents brief lights successively at separate locations to test perception of their spacing and timing. This standard arrangement reveals longer perceived intervals across larger spatial gaps.
Phi phenomenon: The phi phenomenon is an illusion of movement produced by sequentially flashing stationary lights. It concerns perceived motion from stimulus sequences, rather than spatial distance lengthening perceived intervals.
Time perception: Time perception is the experience and judgment of durations, temporal order, and the passage of time. The kappa effect is a systematic distortion of perceived duration.
Stimulus: A stimulus is a detectable event or change capable of eliciting a sensory or behavioral response. Kappa-effect experiments use successive stimuli as the events whose spacing and timing are varied.
Visual apparent motion: Visual apparent motion is perceived movement created by presenting visual stimuli at different locations in sequence. Successive flashes can seem to move, making their spatial path relevant to perceived timing.
Flash-lag effect: The flash-lag effect is the perceived spatial displacement of a flashed object relative to a moving object. It distorts perceived position during motion, unlike the kappa effect’s interval-duration distortion.
Spatial perception: Spatial perception is the ability to perceive the positions, distances, and relationships of objects. The illusion links perceived spatial distance to judgments of elapsed time.
Visual field: The visual field is the region of space visible to an observer at a given moment. Stimulus locations within this field establish the spatial separation relevant to the illusion.