Chess grandmaster Patrick Wolff performs a classic chess memory task (filmed by Daniel Simons and Christopher Chabris). We showed him a card depicting a chess position and he then reconstructed the position on a chess board from memory. He makes almost no mistakes for a typical chess position, but has poor memory for a position in which the pieces were randomly positioned. The video illustrates the powerful effect of expertise on pattern perception and memory. This video is ©1998/2011, Daniel J. Simons & Christopher F. Chabris. All rights are reserved.