Have you watched any tennis or snooker recently. How many times have you seen the players stop dead before the serve or take a shot because someone in the crowd has coughed or flashed their camera. All these years practicing and a small noise can put them off so much that they refuse to play until the noise has abated. What has this got to do with chess strategies? Well I do not condone trying to put your opponent off but I have studied psychology and know that very small changes in behaviour can have a detrimental effect on your opponents concentration. And for me this is all part of the chess strategies we can use.