Adult age and the rate of an internal clock.

Two experiments were conducted to determine whether young and old adults differ in the rate of a hypothetical internal clock. Clock rate was measured as the slope of the function relating actual duration to perceived duration. No age differences were apparent when subjects were asked to judge the duration of a flash of light in Exp. I, or to judge the duration of a dark interval between two light flashes in Exp. II. It was concluded that there is no evidence to support the hypothesis that perceptual and motor speed differences associated with increased age can be attributable to a slower rate of internal time.