So why is this? Why do some societies not encourage casual smiling? I got my answer, or at least part of one, when I stumbled across a new paper by Kuba Krys, a psychologist at the Polish Academy of Sciences. In some countries, smiling might not be a sign of warmth or even respect. It’s evidence that you’re a fool—a tricky fool.

Krys focused on a cultural phenomenon called “uncertainty avoidance.” Cultures that are low on this scale tend to have social systems—courts, health-care systems, safety nets, and so forth—that are unstable. Therefore, people there view the future as unpredictable and uncontrollable.

Smiling is a sign of certainty and confidence, so when people in those countries smile, they might seem odd. Why would you smile when fate is an invisible wolf waiting to shred you? You might, in those “low-UA” countries, even be considered stupid for smiling.

Krys also hypothesized that smiling in corrupt countries would be, um, frowned upon. When everyone’s trying to pull one over on each other, you don’t know if someone’s smiling with good intentions, or because they’re trying to trick you.

To test this theory, Krys had thousands of people in 44 different countries judge a series of eight smiling and non-smiling faces on a scale of honesty and intelligence. He compared their answers to the country’s rankings of uncertainty avoidance from a 2004 study of 62 societies and ratings of corruption.

He found that in countries like Germany, Switzerland, China, and Malaysia, smiling faces were rated as significantly more intelligent than non-smiling people. But in Japan, India, Iran, South Korea, and—you guessed it—Russia, the smiling faces were considered significantly less intelligent. Even after controlling for other factors, like the economy, there was a strong correlation between how unpredictable a society was and the likelihood they would consider smiling unintelligent.

Intelligence and Smiling

In countries such as India, Argentina, and the Maldives, meanwhile, smiling was associated with dishonesty—something Krys found to be correlated to their corruption rankings.

Honesty and Smiling

“This research indicates that corruption at the societal level may weaken the meaning of an evolutionary important signal such as smiling,” Krys writes.

That’s certainly a satisfying explanation. But it’s worth noting that other studies have found there might be other factors, like how hierarchical or masculine a culture is, that play a greater role in emotional expression—which smiling is certainly a part of. And there’s evidence that some cultures don’t value happiness very highly, which would affect how often people there force themselves to break into a grin.