Ehrenstein's brightness illusion

The German psychologist Walter Ehrenstein is remembered for studies two illusions in particular both of which are known variously as the Ehrenstein illusion



"Ehrenstein's brightness illusion" is associated with one of the illusory contour. The black lines of the lattice with their intersections deleted appear to have white discs obscuring the lines, and appearing lighter that the background.

If the colours are reversed then black discs appear.