Photo: Keith Bernstein/HBO

The girl at work who’s always complimenting your (honestly, not compliment-worthy) outfits — what does she want, anyway? A rather paranoid mode of thinking, it’s true, but it’s also one that happens to be backed up by some recent research. “Excessively polite” people were more likely to betray their peers than the less-polite, according to findings presented last month at the Annual Meeting of the Association for Computational Linguistics in Beijing.

Over at Science News, a publication of the nonprofit Society for Science and the Public, Rachel Ehrenberg breaks down the study, which involved the game Diplomacy, a strategy game in which players act as countries in pre-World War I Europe. The game doesn’t use dice or playing cards; instead, players must negotiate and form alliances with each other to move the action forward. A pretty solid strategy for winning the game, Ehrenberg explains, is to act as if you’re on someone’s side — and then proceed to figuratively stab them in the back by launching an attack on their land.

The researchers wanted to use the game to identify any potential warning signs of betrayal. What, if anything, do people who routinely violate the trust of their peers have in common? The answer, according to their observations: Backstabbers tend to play nice. People who were “excessively polite” throughout the game were more likely to betray their opponents than those who spoke in a less-civilized manner.

For example, here’s an exchange between players:

Germany: Can I suggest you move your armies east and then I will support you? Then next year you move [there] and dismantle Turkey. I will deal with England and France, you take out Italy. Austria: Sounds like a perfect plan! Happy to follow through. And — thank you Bruder!

Immediately after this exchange, Austria invaded Germany. In the cynical, yet practical spirit of this study: Keep an eye out for excessive exclamation point and/or smiley-face users. They’re the ones to watch.