Experienced Speed of Time in Durations of Known and Unknown Length

Experienced speed of time was modeled as a function of subjective duration and a negative exponential function was derived. In 3 experiments on the perception of retrospective and prospective durations, using the method of reproduction, speed of time and pleasantness/unpleasantness of the sound indicating the durations were estimated, both on 7-point scales. Since retrospective time perception was being studied, the 120 subjects were not informed that their task concerned time perception when a standard duration (1 out of 10, ranging between 1.3 and 20 s) was presented. The estimates differed for both variables, depending on whether the target was the standard duration, presented first in the experiments, or its reproduction. The exponential function for speed of time was confirmed for the standard duration as target; with the reproduction as target, time passed faster without systematic variations with duration. Unpleasantness varied only slightly and was about half a scale unit less in estimations of reproductions. These findings are attributed primarily to whether the target duration was unknown (the retrospectively presented standard duration) or known (the reproduction).