Abstract
The speed of a visual stimulus has been shown to influence its apparent duration: for low speeds, faster stimuli tend to be judged as longer (Kanai, Paffen, Hogendoorn, & Verstraten, 2006, Journal of Vision, 6, 1421-1430; Kaneko & Murakami, 2009, Journal of Vision 9, 14). This effect has been ascribed to the number of changes that occur within a visual interval. Intervals that contain more changes (i.e., faster intervals) are likely to show time dilation. If this is true, we should not expect to find specific differences in perceived duration for intervals that contain the same number of changes. In this study, we measured the apparent duration of drifting gratings whose speed continuously increased (acceleration) or decreased (deceleration) linearly around an average value (10 °/s). Note that the two conditions (acceleration, deceleration) have the same number of cycles. Subjects had to compare accelerating or decelerating stimuli with comparison stimuli of variable duration that drifted at a constant speed (also 10 °/s) in order to determine a psychometric function. Six speed pairings (from 0-20 to 10-10 °/s) and three standard durations (300, 600 and 900 ms) were investigated. We observed a clear difference between the two conditions. While the perceived duration of the decelerating stimuli showed a mild expansion that did not depend on the rate of deceleration, the accelerating stimuli showed a strong compression, which increased with the rate of acceleration. Duration discrimination thresholds (estimated from the slopes of the psychometric functions) were indistinguishable between the acceleration and deceleration conditions and did not show any dependence on the rate of acceleration or deceleration. Our results cannot be explained by a mechanism that simply reflects the number of temporal features within an interval in determining the perceived passing of time.
Meeting abstract presented at VSS 2012