Abstract
When a brief flash is presented at the same location as a moving object, the flash is perceived to lag behind the moving object to an extent that increases with the speed of the object. Previous studies showed that moving objects appear faster at low luminance as a result of their longer motion trace. Here we examine whether this faster perceived motion also affects the amount of the flash lag at low luminance. We first verified that speed was overestimated at low luminance with our stimulus. We then asked subjects to align a briefly flashed dot with the moving target. Results showed that the flash-lag effect increased with physical speed at both high and low luminance, but there was no additional increase due to the perceived increase of speed at low luminance. We suggest that although motion blur contributes to perceived speed, it does not contribute to the speed information that influences its perceived position.
Highlights
Accurate perception of the position of moving objects is a challenging but critical task for the visual system
A one-way repeated-measures ANOVA with target speed as the factor and the amount of speed overestimation calculated as the difference between the target speed and match speed as the dependant variable showed a significant effect of speed on the overestimation of speed at low luminance (F (2, 6) = 27.6, p
The first experiment showed that a linearly translating stimulus is perceived to move faster at low luminance than an otherwise identical stimulus at high luminance. This replicates earlier findings (Vaziri Pashkam and Cavanagh 2008) but importantly demonstrates that this effect is seen on the compact stimuli we needed for our flash-lag experiments
Summary
Accurate perception of the position of moving objects is a challenging but critical task for the visual system. The visual system, through specialized visual areas dedicated to the analysis of motion (Tootell et al 1995), can extract the motion of objects independent of their position (Wertheimer 1912; Zeki 1991; Addams 1834); motion affects the perception of the position of moving objects (Whitney 2002). One example of such interference is demonstrated by the well-known flash-lag effect. More important for the purpose of our experiment here, it has been shown that the magnitude of the flash-lag effect increases as the speed of motion
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