Speed perception is affected by the Ebbinghaus-Titchener illusion

We examined whether the apparent extent of motion affects speed perception. On the first presentation of each trial, a light dot travelled horizontall y across a central circle of one of the Ebbinghaus configurations (with eit her small or large inducing elements). On the second presentation, observer s adjusted the speed of a dot moving within the central circle alone so as to match the speed perceived in the first presentation. For all stimulus sp eeds (1.3, 2.1, and 5.5 deg s(-1)), the matched speed with small inducing c ircles was systematically less than that with large inducing circles. The f indings indicate that the perceived speed depends on the apparent extent of motion: the larger the apparent size of a frame, the slower the apparent s peed. These results are consistent with the predictions of transposition ef fects in visual motion.