When we smile we share our happiness with others, whether it's because we're happy or feeling flirty. According to a recent study published in the journal PNAS, however, smiles are also linked to cultural differences. People who live in countries with a great influx of migration are more likely to smile in order to maintain "social bonds."

In other words, smiles help break down the language barrier. Emotions themselves are a universal phenomenon people of all cultures experience in reaction to similar events. So although emotions are a natural response, they are influenced by culture. From the way emotions are experienced, to how they are perceived, aspects of emotionally expressive behavior vary based on the culturally normative behavior of that society.

Cultural scripts, a term used by researchers Yuri Miyamoto and Carol Ryff in a 2010 study, describes the cultural norms that influence how people expect emotions to be regulated. They dictate how people should experience and combine both positive and negative emotions. They are also used as a guide for how people should regulate their emotions, which then influences a person’s emotional experience.

In an effort to evaluate how universal facial expressions can be influenced by other aspects of emotionally expressive behavior, Paula Niedenthal, lead author of the study and psychologist at the University of Wisconsin-Madison, and her colleagues decided to examine the psychology of smiling in over 700 peoople in nine countries, including the U.S., Japan, and France. They then compared the results for each country with its migration numbers. This would prove or disprove the researchers’ hypothesis of whether countries without many immigrants would agree on unspoken rules for how much emotion to show in certain situations.

In the survey, the participants were asked what constituted a good reason for someone else to smile. The options varied from “is a happy person,” “wants to sell you something,” and “feels inferior to you.” For each reason to smile, the participants had to pick from among seven choices, from strongly disagree to strongly agree. The researchers then explored each country’s “historical heterogeneity,” which captures the history of a country’s migration in a single number. For example, Canada scores a 63, which means Canada’s current population comes from 63 different countries over the past 500 years. The numbers were compared to an earlier survey that examined the emotional response of 5,000 people from 32 different countries in different scenarios.

The findings revealed countries with greater immigration over the past 500 years were more likely to interpret smiles as friendly gestures compared to those with less migration who believed smiles were linked to social hierarchy. Countries like the U.S. and Canada were more likely to interpret smiles as friendly or happy. Researchers suspect this may be a way of overcoming a language barrier in countries that are a mix of different languages and cultures.

“We think an absence of shared language and shared culture would push people toward greater nonverbal expression of emotion,” said Niedenthal, in the news release. “Because otherwise you wouldn’t know what the other person was feeling or thinking or liking or disliking. And you need to be able to communicate those things to facilitate commerce and government, to survive and prosper together.”

In comparison, countries that have a less diverse past — like China and Japan, who both scored 1 — hold a more complex meaning when it comes to smiling. The researchers suspect countries without many immigrants, like Japan, would agree on rules for how much emotion to show in certain situations. Typically, subordinates in Japan tend to use smiles around their bosses to hide feeling upset.

“In homogenous cultures, they have hierarchies that have been established over the course of many, many generations, and they tend to view dominance smiles as more frequent or important,” Niedenthal said about Japan and other homogenous countries.

Niedenthal hopes to replicate this study within the U.S. She is now in the early stages of studying emotional expression throughout the states and suspects results will vary based on the different amounts of long-history migration. She and her colleagues are currently working with census data to determine the migration numbers needed to distinguish the differences between Southwest, New England, or other regions. Her research will explore in-depth where smiles and frowns are used more in certain pockets of the U.S.

You can’t talk about emotion without talking about culture. Cultures differentially affect emotions, meaning it is important to explore cultural contexts in order to understand emotions. After all, a country’s emotional culture can give clues of why a group of people may act or behave a certain way.

Sources: Gilboa-Schechtman E, Hess U, Kamble S et al. Heterogeneity of long-history migration explains cultural differences in reports of emotional expressivity and the functions of smiles. PNAS. 2015.

Miyamoto Y and Ryff CD. Cultural differences in the dialectical and non-dialectical emotional styles and their implications for health. Cognition & Emotion. 2011.