poker face

A poker player has two ideal options:

1) Sit perfectly still. Be non-responsive and maintain a blank expression.

2) Randomize. Respond erratically so that the opponent can not pick up any reliable indicators.

The problem with the second approach is two folds:

1) It is energy intensive in comparison to the first approach.

2) Human beings often detect spurious patterns in randomly generated data. (This phenomenon is called Pareidolia.) Your opponent may devise a strategy based on his interpretation of your random moves. It will be very difficult for you to unravel this strategy and respond in a cogent way.

Update (July 2012): In finance, most people fall prey to Pareidolia, including those "sober-thinking", contrarian traders:  "For bubble and anti-bubble thinking are both wrong because they hold the truth is social. But if the herd isn’t thinking at all, being contrarian—doing the opposite of the herd—is just as random and useless." (From Blake Masters' notes on Peter Thiel's course at Stanford University)