You may want to save the smile for when you’re losing, not winning, according to a study done at the University of Southern California.
The study, funded by the U.S. Army Research Laboratory and presented by the USC Institute for Creative Technologies, found that smiling decreases your odds of continuing your winning streak against the same opponent.
Researchers had 370 participants play a game in which they decided to either “split” or “steal” a pot of money, as with the (hilariously titled) British game show Golden Balls. The rules are simple: If both players choose to split, they split the pot. If both choose to steal, they both lose. If one person chooses to steal while the other splits, the person who chose to split wins the pot. The participants played over Skype, and their reactions throughout the matches were recorded and encoded with emotion-tracking software.
Here's the interesting thing: The people who smiled as they won were less likely to keep winning because their opponents were more likely to try to steal to get payback rather than share, even if getting payback means putting their own best interests aside.
On the other hand, a smile during a loss might help your odds of winning. While the people who stole successfully and smiled about it seemed to give their opponents a burning desire to get payback, those who smiled when they lost were viewed as cooperative. This gave their opponents a feeling of mutual success and made them more willing to cooperate, researchers hypothesize.
In that case, being a good loser will do you more good than gloating about your wins. So next time you're in a cutthroat match of your favorite game—take note, Settlers of Catan aficionados—make sure you use your smile to your advantage, not your opponent's.