Textured backgrounds alter perceived speed

Both the luminance contrast of an object, and the nature of the background texture over which it moves, are known to influence its perceived speed. In this study the effect of object contrast upon perceived speed was investigated for targets moving across textured patterns of various contrasts. Experiment 1 showed a strong effect of contrast for objects moving over homogenous backgrounds, that was reduced or abolished if the object moved over a textured background. A further experiment suggested that this reduction may be the result of an increase in target visibility, perhaps as a result of additional 'second order' motion signals produced by motion over texture backgrounds. A final experiment suggested that two processes were occurring: (1) higher contrast backgrounds appeared to increase the perceived speeds of all objects; and (2) that higher contrast backgrounds eliminated the contrast induced changes in perceived speed.