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Are unconcious expressions from a 21 year old the same as a 40 year old?

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Absolutely. More important than tells, however, are betting patterns. Read Harrington vol. 1. There is a lot there that can be applied to cash games. Tells are very applicable to newbies, but players with more experience, even the bad ones, cover their tells better. It's more important to know the types of hands the person plays and in what situations they play them to get an idea if they have you beat. The main thing I learned from Caro was watching the players and not the flop to get their reaction as to whether or not the flop helped them and going from there.