The most important concept when studying poker tells is correlation. Correlation is the act of establishing a relationship between two things. Applied to poker, correlation refers to matching a player’s tells with specific situations. Once you’ve correlated a tell with a specific situation, this enables you to draw conclusions when you see that same tell in the same situation in the future.
Observing how your opponents behave in certain kinds of situations (for instance, when making a pure bluff on the river, or when value-betting with a strong hand) allows you to correlate their behavior with their hand strength. The more times you notice a connection between a player’s behavior in a specific situation and his hand strength, the stronger the correlation is, and the more weight you can give to that information.
You should always keep in mind that tells are tendencies. By which I mean, they’re something a specific player is more prone to do than not do. Tells are not something a player performs every single time (although I’ve seen tells that are probably 99% reliable for a player). Just as you’d gather information about an opponent’s play (for example, what percentage of the time he raises pre-flop), you can gather information on the reliability of his tells (for example, the percentage of the time a player’s eyes glance towards his lap as he’s in the act of bluffing).
Some tells will be statistically insignificant, meaning there is no correlation between hand strength and behavior. Some tells will be very significant, meaning that they will have a very good chance of having a specific meaning. Those are the most useful tells and the ones we want to find.
But even a tell that is only slightly reliable can be useful in situations that we think are break-even spots from a fundamental strategy standpoint. (For instance, if we think it’s even-money whether to call a river bet or fold to that bet, then a tell that is only correct 60% of the time will still be very useful in the long run.) Generally, though, if you can’t fairly easily spot tells that seem likely to be statistically significant, you should move on and either study a different player or study another behavior of the same player.
Most of the common tells I will describe in this book are tendencies of a large percentage of the poker-playing population. But of course not everyone will have the same tells. Some players will exhibit tells that very few other people exhibit. (For example, I’ve played with a few people who slump in their seat and look dejected after bluffing, but this is the opposite of most players’ behavior.) Some players will have eliminated most of the commonly-seen tells, but might have quirks of their own that are highly reliable. Some experienced players will have virtually eliminated their tells through hard work and experience.
So while you should learn the common poker tells, you should always keep in mind the importance of correlation. As a general rule, you should almost never act on potential tells you’ve spotted unless you have already correlated them with a player’s past behavior. Only when you’re very comfortable in your reading ability should you stray from this advice.