The checkerboard is vertical or horizontal but appears to tilt. Parts of the figure appear to move. No matter in what position you warming you Chair, The figure in this picture will appear to move as long as you staring it.




When slightly tilted line segments are aligned horizontally like the figure, the whole array appears to tilt toward the tilt of the line elements. This is a reversal of the Zollner illusion or acute-angle contraction.