'ILLUSIONS' The above figure is a two-dimensional pattern on a flat screen, but it is perceived as a transparent, three-dimensional cube. Stare at it for a few seconds and it will change to face in a different direction. Carry on staring and it will flip back to the original cube. Both cubes are equally compatible with the two-dimensional data on the retina, so the brain 'happily' alternates between them. Neither is more correct than the other. However the Necker Cube is miss-leading because it suggests that the two ways of seeing are equally good.
