Movie S1.

Paradoxical stabilization of a moving frame. The right edge flashes red at the left end of the frame’s travel and the left edge flashes blue at the right end. Participants matched the perceived separation between the flashes with the markers on the upper right. In this example, the frame travel is longer than the frame size so the red flash is physically to the left of the blue flash. Nevertheless, blue is seen left of red.
  • The movie starts very slowly to make the positions of the flashes clear: red on the left, blue on the right.
  • However, after several seconds, when the frame reaches full speed, you may see the blue flash to the left of the red.
  • The markers above to the right are adjusted to match the perceived separation.
  • The frame will fade out briefly to reveal that red is really to the left of blue.