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Aurelio Bruno, Inci Ayhan, Alan Johnston; Influences of stimulus predictability on its perceived duration. Journal of Vision 2010;10(7):1413. doi: 10.1167/10.7.1413.
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Our ability to judge how long a visual stimulus lasts has been proposed to rely on an internal content-dependent clock, which determines apparent duration using a “predict and compare” strategy. For example, a prediction of what the visual world will look like in 100 ms is continuously compared to the sensory input. When the prediction matches the visual input, the system determines that 100 ms have passed and resets the prediction (Johnston, In Attention and Time, edited by Nobre & Coull (OUP, Oxford), In press). If this is true, it is reasonable to expect that the degree of predictability of a stimulus has an influence on its perceived duration. In this experiment, we asked subjects to compare the relative duration of a 10 Hz drifting comparison stimulus (variable duration across trials) with a standard stimulus (fixed duration, 600, 1200 or 2400 ms) with different degrees of predictability in different sessions. The standard could be static, drifting at 10 Hz (these two conditions are highly predictable) or mixed (a combination of static and drifting intervals). In this last condition the degree of predictability of the stimulus was low: a static interval always followed a drifting one, but we assigned a duration between 100 and 200 ms to each subinterval, randomly, within and across trials. For all standard durations, the unpredictable (mixed) stimulus looked significantly compressed (∼20% reduction). The drifting and the static stimulus differed from the actual duration only for one standard duration in each case (mild expansion for drifting at 2400, compression for static at 1200 as predicted by Brown, 1995, Perception & Psychophysics, 57(1): 105-116). These results support the idea that interfering with the predictability of a stimulus may disrupt the continuity of a “predict and compare” mechanism and therefore, influence its apparent duration.
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