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Maryam Vaziri Pashkam, Patrick Cavanagh; Effect of speed overestimation on manual hitting at low luminance. Journal of Vision 2010;10(7):1076. doi: 10.1167/10.7.1076.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have reported an overestimate in the perceived speed of moving objects at low luminance (Hammett et al 2007, Vaziri-Pashkam & Cavanagh 2008) and we have shown that this overestimate is a result of the longer blurred trajectory left by the moving stimulus at low luminance. Here we investigate whether this cue of extended motion trace affects action as well as perception by testing the accuracy of hand motion to a translating target at low luminance. We first verified the low-luminance effect on perception with two stimuli presented successively, one at high (mean luminance 75 cd/m2) and one at low luminance (0.15 cd/m2). Subjects had to decrease the speed of the low luminance stimulus by approximately 30% to match the apparent speed at high luminance. In the second experiment, subjects were asked to make rapid hand movements towards the moving targets so that their fingertip would land on the center of the moving random dot pattern. Vision of the hand was blocked to prevent visual feedback so that the accuracy of the landing depended on the speed estimate for the moving target. Results showed that the landing position of the finger was significantly farther ahead of the target at low luminance suggesting that the programming of the hand motion was based on an overestimated target speed. Based on the timing of the hand movement and its landing position, we derived the target speed used to plan the hand movement and found it to be about 10-15% too fast at low luminance compared to high luminance. We suggest that overestimation of perceived speed based on the extended blur cue affects our motor performance at low luminance conditions.
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