Figure 2.
Stochastic Stimuli Can Bias Duration Judgment
(A) Simulated judgments of the apparent duration of one-second-long noise stimuli played at different speeds. Mean estimated durations are shown normalized by the grand average estimate over all playback speeds. Rapid playback of the stimuli leads to overestimation.
(B) Experiment 1, two-alternative forced choice (2AFC) task. Observers reported which of two smoothed Gaussian noise stimuli, presented sequentially at fixation 1 s apart, appeared to last longer. Frames of one stimulus were played rapidly and the other slowly, with the order of speeds counterbalanced. The duration of the first stimulus varied pseudorandomly between 500 and 650 ms. The second differed by an interval Δ that was adjusted by two independent staircases to find points of subjective equality (PSE) in the slow-rapid and rapid-slow conditions. Bars show the average value of Δ at PSE (n = 8; standard error shown); in both cases, the slow stimulus needed to be longer for subjective isochrony (p < 10−6).
(C) Experiment 1, reproduction task. Subjects were asked to depress a key to match the duration of a smoothed noise stimulus presented at fixation at varying playback speeds. Durations of stimuli played rapidly were overestimated on average (n = 6; standard error shown). (See also Figure S2.)