THE SCINTILLATING GRID ILLUSION

Disk-shaped luminance increments were added to the intersections of a Hermann grid consisting of medium grey bars on a black background. Ill usory spots, darker than the background, were perceived as flashing wi thin the white disks with each flick of the eye. This striking phenome non may be referred to as the scintillating grid illusion. We determin ed the conditions necessary for cancelling the Hermann grid illusion, as well as the luminance requirements and the size ratio between disks and bars that elicits the scintillation effect. The fact that scannin g eye movements are necessary to produce the scintillation effect sets it apart from the Hermann grid illusion. (C) 1997 Elsevier Science Lt d.