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Poker tells: It's in the arms, not the face -- maybe

There’s a good bit of fuss being made in the poker world over a study published in the prestigious journal Psychological Science by Michael Slepian and colleagues at Stanford University. They found that information in a player’s arms and hands was more reliable in assessing the strength of a player’s hand than what could be picked up from their face. Slepian’s findings are intriguing (go here for more on Slepian and his research) but need to be seen in the context of an on-going, live poker game. 

Slepian had people view short snippets of videos (less than 2 seconds) from the 2009 WSOP and had them judge the strength of the hands the players were holding. Some saw just the face, some the entire body above the table and others just the arms and hands. Participants seeing just the face were unable to judge the strength of the held hand. In fact, they were worse than chance – not by a lot but enough to suggest that players at this level can use facial expressions deceptively. Participants who saw the full upper body were at chance in estimating hand-strength. But, fascinatingly, participants who only saw the hands and arms were significantly better at judging hand-strength. Importantly, even participants who had no experience with poker could do this. The correlations weren’t huge (.07 where 1.0 is a perfect correlation) but they were statistically reliable.

The obvious question is what are people picking up here? What’s the tell? Slepian went back and did another study this time asking participants to judge, not hand-strength, but how confident they thought the player was and, on other occasions, to judge how steady their arms movements seemed. Asking people to look at assumed confidence improved their ability to judge hand-strength considerably (the correlation was .15). Asking them to estimate how smooth the arm movements were produced a dramatic increase in accuracy (correlation jumped to .27).

The lesson seems simple: try to judge how smooth the motions of your opponents are when they push chips into the pot. Don’t worry about their face. Don’t try to judge levels of stress or nervousness. Just examine the raw physical movements and look for smooth versus jerky or hesitant movements.

But, take care. As always, in poker things are more complex than they first appear. These video clips were from experienced players and they were very short. It’s not obvious that the average Joe or Jane playing $1 - $2 at your local poker room will display these patterns of facial expression and arm movements. It’s also unclear whether reliable facial information can be picked up if one looks at how expressions change (or not) over time. Experienced players often stare at an opponent’s face, not for two seconds, but for extended periods of time. And, of course, these results don’t tell us what the data would be like if expert poker players were the participants. It is possible that top professionals could pick up information in the videos that novices couldn’t.

Nevertheless, I applaud Slepian and colleagues for this study. The more we look at the game the more we’re going to learn about it and the folks who play it.

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