It is possible that a person, by body language, or some other involuntary physical action, will communicate what the cards are saying. Much has been written about tells. They differ from the tricks and wiles of poseurs because they are involuntary, and hence, presumptively sincere.

It is possible, of course, that an experienced actor might be able to sell an idea to the rest of the table by setting up a conscious and contrived "tell." Later on, he or she could then repeat it and thereby deceive an opponent. The problem with that is that the deception will only work once. When a good player thinks that some behavior is a possible tell, he or she will keep a watch for it, and rely on it only after confirming the correlation of the tell with the cards. The minute the trigger is pulled on a fake tell, it is no longer available, and some other fake tell will have to be adopted and cultivated though several hands. It would be immensely unlikely for any player to manipulate the others with more than two fake tells in the course of a game. The other players should not even fall for it more than once, if that.

A real tell is a mannerism, like stroking the left side of the mustache with the left hand while thinking about a bet. If this behavior never precedes a bet on a "pat" hand, then it is indicative that the next action will be a bluff or semi-bluff (if not a fold). Professional Hold'em players wear dark glasses at the table because sometimes the pupils of the eye can dilate and give away a situation of excitement, doubt or stress. Breathing and blood flow likewise respond to how the body processes tension or excitement, generating things like blushes or shallow breaths. One poker player many years ago had telltale ears that would turn a distinctive shade of red at the tops whenever he had a great hand. No degree of stoniness in the "poker face" could ever overcome the clarity of the signals from his "non-poker ears!"

Other correlations of cards and behavior can be more subtle. For example, even a very seasoned player may fall silent when watching play unfold in a game where he has some worry about his position. If otherwise, he's a little chatty, the absence of talk can be a tell. Experienced players generally adopt the quiet approach from the outset so that they can play every hand with exactly the same behavior.

How does one discover a tell? The main two resources required are concentration and memory. In a reasonably long session one might play 300 hands of poker. The first 25 or so should be research experiments, in which the player really focuses one by one on the other players and sizes them up. Are they disciplined? Do they appear to have experience or guidelines that help the play go quickly? Are they emotionally contained or expressive? Are they analytical or intuitive in their plays? Are they loose or tight? A good player will be able to observe all this and remember. Then, at any time in the game, if a certain player repeats a behavior evidenced in earlier hands, like calling the previous player's bluff "on principle," without the cards or the pot odds to support such a move, then that repetition should be registered. It was a mistake that will be repeated again perhaps. Though this observation may be more of a "proclivity" than a "tell," it qualifies as the sort of thing that gives an edge to the poker player who sits at the table with eyes and ears wide open and the mind primed to jot it all down.

The question might arise, "How important are tells?" There are two answers. First, many authors will say that worrying about tells distracts the player from what really counts, namely the cards and the bets. There is so much else to think about that tells should be at the bottom of the list. This is probably a correct position, especially for beginners.

But the second answer is that successful poker involves reading people better than people read you. True, there are other aspects to the game, like the probabilities, and they require thought and attention as well. But whether it is expressed as "looking for a tell" or simply as "sizing up how another player plays," this behavioral aspect of the game cannot be ignored. Indeed, it is probably the essence of successful play.