Perceived speed in peripheral vision can go up or down

We measured the perceived speed and contrast of patterns in peripheral vision relative to foveal patterns for a range of eccentricities at both mesopic and photopic levels. The results indicate that, at high (photopic) luminance, patterns appear slower when viewed peripherally rather than foveally, but at low (mesopic) luminance fast-moving patterns can appear faster when viewed peripherally. When perceived contrast is equated, perceived speed reduces as a function of eccentricity in a speed-independent manner. Peripheral stimuli appear faster or slower than foveal stimuli depending upon luminance - an image parameter known to influence the gain of magno and parvocellular cells. We conclude that speed encoding in the periphery is consistent with a ratio-type speed code that is weighted by ganglion cell density.