If you stare at this image, you will see flashing black dots appear over the intersections of the black squares. The contrast of colors causes our retina to retain and transfer the black color to the light parts. As soon as we try to directly visualize the “ghost” black dot, it disappears, giving the impression that the dots appear and disappear continuously.
An illusion of bright network. Difference in shape, position, color, 3D and converge to produce the illusion of black dots at intersections