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Doga Gulhan, Inci Ayhan; The perceived duration of global motion in random dot kinematogram (RDK) displays. Journal of Vision 2016;16(12):1083. doi: https://doi.org/10.1167/16.12.1083.
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© ARVO (1962-2015); The Authors (2016-present)
Apparent duration can be manipulated in a local region of visual field by adaptation to motion or flicker (A. Johnston, D. H. Arnold, & S. Nishida, 2006; I. Ayhan, A. Bruno, S. Nishida, & A. Johnston, 2009). Duration compression occurs in the absence of changes in temporal frequency or speed, implying separate encoding of duration and temporal frequency. Here we examine the effects of variation in the temporal features of local signals on the apparent duration of global motion using RDK patterns at 50% coherence level (with noise dots having a vector sum speed of 0deg/s). In different conditions, the lifetime of individual dots were either fixed at 150ms or varied between 50-250ms as randomly selected from a normal distribution. Additionally, the effect of variation in the speed of individual dots had also been manipulated to target fast and slow global motion mechanisms. In blocked trials of a 2-AFC task, subjects compared the duration of a comparison stimulus (variable duration across trials; 150ms dot-life; 2.5 or 9deg/s dot speed) to the duration of a standard stimulus (fixed at 550ms across trials) with individual dots either having fixed (150ms) or variable (50-250ms) dot-life and fixed (2.5deg/s or 9deg/s) or variable (1-4deg/s or 6-12deg/s) speeds. The perceived duration was defined as the point of subjective equality of the psychometric function. Across all speed conditions, we found a relative duration expansion (10%) in conditions where the lifetime of dots had been variable in comparison to those where the dot lifetimes was fixed, whereas varying the speed of individual dots around the same average speed for slow (2.5deg/s vs 1-4deg/s) and fast (9deg/s vs 6-12deg/s) ranges had no relative effect on the apparent duration. Control experiments have shown that neither changes in perceived speed nor the allocation of attentional resources can explain this temporal expansion.
Meeting abstract presented at VSS 2016
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