Calling a Bluff: Is It All In the Arms?

Annie Duke was on track for a promising career in psycholinguistics, when she abruptly abandoned the academic life for the high-stakes world of poker. That was two decades ago, and since then she has won a slew of honors, including the prestigious World Series of Poker “bracelet”—plus lots  of cash. She is known among other poker players as the Duchess of Poker.

In a recent Radiolab interview, Duke talked about how she weighs risk and certainty and doubt in deciding to hold or fold. It’s largely math, but not the straightforward odds of drawing to an inside straight. She computes odds and acceptable losses over long periods of time. Surprisingly, she said, she gets very little help from other players’ “tells”—the inadvertent facial expressions that give away emotions and intentions. Pros are very good at “disappearing” into the well-known “poker face.”

We all know the expression “poker face” because the face is where we expect to find meaningful information. But what if poker players are looking in the wrong place? New research out of Stanford University now suggests that poker players’ arm movements may betray the strength of the hands they are holding, even when their faces remain expressionless. What’s more, it appears that even non-players can detect these motion “tells” in professional card players.

Michael Slepian, a graduate student in Nalini Ambady’s psychological science lab, has been studying the way observers perceive poker players’ non-verbal signals, specifically arm motions, as cues to their intentions—and the value of their poker hands.  In a simple experiment, he extracted 20 very brief video clips—less than two seconds each—of players in the 2009 World Series of Poker. He recruited non-expert volunteers to view the clips, but only some saw whole-body shots, while others saw faces only, and still others arms only. Based on what they saw, the volunteers judged the quality of the hands that the players were holding.

The findings were clear-cut. Judgments based on facial expression were worse than chance. That is, the poker players succeeded not only in hiding their thoughts about their chances, but in deceiving onlookers. By contrast, those who saw arm movements accurately judged the quality of the players’ hands. The movements were unintentional “tells” about players’ hidden thoughts and intentions.

Players who are holding strong hands—a full house rather than a low pair—should be more confident, and it’s possible that this confidence is expressed through the arms. But what about the arms, specifically, is revealing? Slepian knew of previous work showing that anxiety disrupts the smoothness of body movement, so he figured that confidence—lack of anxiety—might be embodied in smooth motion. In a second experiment, he had volunteers judge players’ confidence and then, independently, judge the smoothness of the players’ arm motions. He figured that if confidence is indeed embodied in smooth movement, then smooth arms movements might be the “tell.”

And that’s just what he found. As described in a forthcoming article in the journal Psychological Science, both judgments—player confidence and smooth arm movement—were strong indicators of the quality of players’ cards. So it seems quite likely that players who are holding winning hands reveal their confidence when they push their chips to place a bet.  Remember that these players were the best in the game, competing in the high-stakes World Series of Poker—so they were motivated to hide every thought and emotion. Yet based on observing minimal information during less than two seconds of play, average people were able to decode the hands at the table—and call the bluffs.

Wray Herbert’s blogs—We’re Only Human” and “Full Frontal Psychology”—appear regularly in The Huffington Post and elsewhere.