Grid Illusion

Try and count the black dots....

If you keep your eyes on the black dots, they appear to form and vanish at the intersections of the horizonal and vertical lines. The effect is diminished if one is very close to the screen, further away or if one views at a 45 degree angle.

This illusion is known as the Scintillating grid, and was discovered by E. Lingelbach in 1994. It is a modification of the Hermann grid illusion.