A regular two-dimensional arrangement of squares separated by vertical and horizontal "canals." Looking at the grid produces the illusion of gray spots in the
white area between square vertices.
The illusion was noted by Hermann (1870) while reading a book on sound by Tyndall
(1869).
Fineman, M. The Nature of Visual Illusion. New York: Dover, pp. 139-140, 1996.Hermann,
L. "Eine Erscheinung simultanen Contrastes." Pflügers Archiv für
die gesamte Physiologie3, 13-15, 1870.Lingelbach, B. and
Ehrenstein, W. H. Jr. "Das Hermann-Gitter und die Folgen." http://www.leinroden.de/304herfold.htm.Lloyd,
S. J.-A. "The Hermann Grid." http://web.mit.edu/sjlloyd/www/Perception/.Spillmann,
L. "The Hermann Grid Illusion: a Tool for Studying Human Perceptive Field Organization."
Perception23, 691-708, 1994.Tyndall, J. Der Schall.
Braunschweig, Germany: Vieweg, 1869.
