Imagine you are sitting at a poker table with a stranger whose play strategy — how he bets and bluffs — is unknown to you. You are dealt a two-card hand. Your opponent raises. Will you call or will you fold? How do you decide? Conventional wisdom says you look at your hand, gauge the chances of winning based on your cards, and look for clues of bluffing in your opponent’s face and body language. However, recent research published in PLoS One shows that your first impression of the opponent’s trustworthiness influences your decision and that you fold more frequently when the opponent looks trustworthy than when the opponent keeps a neutral expression or a poker face.

Researcher Erik Schlicht and collaborators study a group of 14 novice poker players in a simplified Texas Hold’em. Each poker player is dealt two cards and allowed to see the face of his opponent on the computer screen. The player has to decide if he will fold or call. If he folds, he loses 100 chips that round. If he calls, then he may win or lose 5000 chips depending on how good his hand is compared to his opponent’s. The face of the opponent changes every round. After 300 rounds, the players are awarded money based on their wins and losses during the game.

The opponents’ faces are actually digitized images of 100 real faces; each modified to appear in 3 slightly different versions: trustworthy, neutral, or untrustworthy. For example, happy and attractive faces are associated with trustworthiness, and may include attributes such as increased distance between the eyes and the eyebrows. Angry or threatening faces are associated with untrustworthiness, and may include attributes such as corners of the mouth drawn down. Neutral faces, the canonical poker faces, show neither positive nor negative expressions. The experiment shows that players take longer to make a decision and fold more often when presented with trustworthy faces than with neutral and untrustworthy ones. The players seem to assume that their trustworthy-looking opponents are not bluffing.

The current study suggests that poker players make a rapid assessment of opponents’ facial expression and use that information to make a decision about the opponents’ behaviors and their intentions. Other studies indicate that this assessment occurs within the first tenth of a second and may involve the amygdala, the brain region known to process information about memory and emotions. We size someone up, so to speak, based on our first impression of his face, and assume that he will behave according to how he looks. In this case, we assume that a trustworthy-looking person would not bluff as much as a neutral- or untrustworthy-looking one.

In an actual poker game, players observe each other’s betting and bluffing strategies after each round and factor those into their decision. On the other hand, if you are playing poker with opponents who do not know your strategies, then appearing trustworthy (as opposed to appearing threatening or keeping a poker face) may benefit you by inducing your opponents to make mistakes and fold more often.

References

Schlicht, E., Shimojo, S., Camerer, C., Battaglia, P., & Nakayama, K. (2010). Human Wagering Behavior Depends on Opponents’ Faces PLoS ONE, 5 (7) DOI: 10.1371/journal.pone.0011663

Oosterhof, N., & Todorov, A. (2008). The functional basis of face evaluation Proceedings of the National Academy of Sciences, 105 (32), 11087-11092 DOI: 10.1073/pnas.0805664105