Stimulus range effects in temporal bisection by humans.

Two experiments with human subjects, using short-duration tones as stimuli to be judged, investigated the effect of the range of the stimulus set on temporal bisection performance. In Experiment 1, six groups of subjects were tested on a temporal bisection task, where each stimulus had to be classified as "short" or "long". For three groups, the difference between the longest (L) and shortest (S) durations in the to-be-bisected stimulus set was kept constant at 400 msec, and the L/S ratio was varied over values of 5:1 and 2:1. For three other groups, the L/S ratio was kept constant at 4:1 but the L-S difference varied from 300 to 600 msec. The bisection point (the stimulus value resulting in 50% "long" responses) was located closer to the arithmetic mean of L and S than the geometric mean for all groups except that for which the L/S ratio was 2:1, in which case geometric mean bisection was found. In Experiment 2, stimuli were spaced between L and S either linearly or logarithmically, and the L/S ratio took values of either 2:1 or 19:1. Geometric mean bisection was found in both cases when the L/S ratio was 2:1, but effects of stimulus spacing were found only when the L/S ratio was 19:1. Overall, the results supported a previous conjecture that the L/S ratio used in a bisection task played a critical role in determining the behaviour obtained. A theoretical model of bisection advanced by Wearden (1991) dealt appropriately with bisection point shifts discussed above but encountered difficulties with stimulus spacing effects

Is subjective duration a signature of coding efficiency?

Perceived duration is conventionally assumed to correspond with objective duration, but a growing literature suggests a more complex picture. For example, repeated stimuli appear briefer in duration than a novel stimulus of equal physical duration. We suggest that such duration illusions appear to parallel the neural phenomenon of repetition suppression, and we marshal evidence for a new hypothesis: the experience of duration is a signature of the amount of energy expended in representing a stimulus, i.e. the coding efficiency. This novel hypothesis offers a unified explanation for almost a dozen illusions in the literature in which subjective duration is modulated by properties of the stimulus such as size, brightness, motion and rate of flicker