Cover picture: Rotating Snakes, by Akiyoshi Kitaoka, adapted by Bevil Conway. In this powerful static motion illusion, the direction of illusory motion is yellow —> black —> blue —> white. Psychophysical and physiological experiments described in our paper show that the critical feature of the illusion is the luminance contrast of the elements compared with the average gray of the entire display. Direction selective neurons in primary visual cortex and the motion area [middle temporal area (MT)] respond to the luminance contrast of the elements in a configuration-dependent way, serving as the physiological building blocks for the illusion. For details, see the article by Conway et al. in this issue (pages 5651–5656)