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Maryam Vaziri Pashkam, Patrick Cavanagh; Apparent speed increases at low luminance. Journal of Vision 2006;6(6):580. doi: https://doi.org/10.1167/6.6.580.
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© ARVO (1962-2015); The Authors (2016-present)
Several visual attributes have been shown to change the perceived speed of moving objects regardless of their real speed. In this study we investigated whether changing the mean luminance of a rotating radial grating affects its perceived rotation speed. The stimulus was a circular disk with 5 radial black spokes on a white background, rotating around its center. A two-interval speed matching procedure was used. In the first interval, subjects viewed the disk at a low luminance level (1 cd/m2), rotating at one of three test speeds (4.2, 8.3, and 12.5 Hz). In the next interval, subjects viewed the same grating at high luminance (60 cd/m2) and adjusted its speed until it matched the apparent speed from the first interval. A control was also run with both intervals at high luminance. The results show that the apparent speed of a 8.3 Hz test viewed at low luminance was matched to a higher speed (10.8 Hz, a 30% speed up) at high luminance. The effect was smaller at 12.5 Hz (10% speed up at low luminance compared to high) and absent at 4.2 Hz. Results with gratings having fewer spokes suggested that the effect was specific to temporal frequency rather than rotational velocity.
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