RACHEL MARTIN, HOST:
Let's talk poker. Dealer, let me see those cards.
(SOUNDBITE OF FILM, "COOL HAND LUKE")
WAYNE ROGERS: (As Gambler) King three. You got a four. Queen deuce gets a five, and a pair of sevens gets a john, and the big ace gets slap in the face. OK, you still do the talking.
MARTIN: That's a poker game from the movie "Cool Hand Luke." Poker, of course, is a game of deception. You have to play your bet based on the cards you think your opponent has. And if you think they've got good cards, you should probably fold. But there's always a chance the other guy is bluffing.
(SOUNDBITE OF FILM, "COOL HAND LUKE")
GEORGE KENNEDY: (As Dragline) A handful of nothing. You stupid mullethead, he beat you at nothing.
PAUL NEWMAN: (As Luke Jackson) Sometimes nothing can be a real cool hand.
MARTIN: Well, it turns out a person's cool, confident hands, as opposed to her tight-lipped poker face, might be the best place to look if you're trying to guess her cards, which leads us to the research of Mike Slepian. He's currently a visiting scholar in Stanford University's psychology department. He studies the way our intentions can influence our movements, and he was looking for a real-world example.
MICHAEL SLEPIAN: When people are playing the game of poker, they move chips into the center of the table. And we're like, oh, well what if how good their poker hand is influences how they move their chips into the center of the table. And if so, can people sort of decode, maybe, their quality of their poker hand without them, obviously, wanting to reveal their poker hand.
MARTIN: That would be valuable information. So what did you find out? Can you apply this to poker?
SLEPIAN: So you can. So we showed participants videos of professional poker players playing in the World Series of Poker. And participants watched either just players placing bets but only their faces, or they watched their whole bodies, or they watched just their arms pushing chips into the center of the table.
And it turned out that people couldn't do it from just the whole body. They couldn't guess accurately how good a poker hand was. They couldn't do it for their face. In fact, they were a little bit worse than chance, suggesting that the facial cues players were sort of admitting were deceptive. But when just looking at the arms, they could tell how good professional poker players poker hands were.
MARTIN: Wow, the truth is in the arms. Why does that make sense? What is it about our arm movements, and that one in particular - moving chips into the center of a table, that's so revealing?
SLEPIAN: So it could be, if you have a really good hand and you feel confident about that, you might just push the chips into the center of the table just a little bit more smoothly. And actually we found that if we have participants rate how smoothly is this person putting chips into the center of the table, the smoother they're doing it, the better their poker hands were.
MARTIN: Do you play poker?
SLEPIAN: I actually don't. Maybe I should start.
MARTIN: (Laughter) Mike Slepian is a visiting scholar at Stanford University. Transcript provided by NPR, Copyright NPR.