Perceptual Time Dilation
Kappa Effect
A temporal perceptual illusion where in perceiving a sequence of consecutive stimuli, subjects tend to overestimate the elapsed time between two successive stimuli when the distance between the stimuli is sufficiently large, and to underestimate the elapsed time when the distance is sufficiently small.
Origin
Japanese psychologist Jun-ichi Abe first documented the phenomenon in 1935, calling it the "S-effect" in studies of visual timing. Nearly two decades later, John Cohen, C. E. M. Hansel, and J. D. Sylvester renamed and formally described it in a 1953 paper, "A New Phenomenon in Time Judgment," published in Nature — giving it the name kappa effect that endured. Their work established it as a distinct category of spatiotemporal perception research.