A new study opens a fascinating window on how people communicate without words, and how some of the sounds people make to express emotion can be understood across cultural barriers.
When we communicate, we don't just use words. Non-verbal communication is important, too.
If you're talking face-to-face, things like facial expression, eye contact, and how close you stand can be an important part of the message.
There's also what researchers call "non-verbal vocalizations" – sounds that send a message without using words.
But how universal are these messages?
That's what Disa Sauter wanted to find out.
"And we were specifically interested in emotional expressions in the voice – so things like laughter, crying, sighing, grunting – those kinds of noises that we all make, but what do they actually mean?"
What do they mean and, more specifically, do they mean the same things to people in different cultures?
"So to look at that, we studied a group called the Himba, who are a culturally isolated group, so a group that doesn't really have anything to do with other groups. And they live in the north of Namibia in Southwest Africa," Sauter explained in a telephone interview.
The Himba participants in the study live a life that is about as isolated as you can be in the modern world. The other group in the study included native English speakers in Europe.
People in both groups were asked to make sounds that expressed emotions like joy or anger without using words.
So for example, they were told to make a sound like they just realized they had eaten some rotten food.
Researchers recorded the sounds, then played them for people in the other group to see, for example, if the Himba recognized the sound of disgust that the Europeans made, and vice versa.
They sound a lot alike, which may be why both groups recognized the sound as registering disgust.
Sauter found that the sounds conveying negative emotions could be understood across cultural boundaries more readily than the sounds of positive emotions.
She says that could be because negative emotions might be older, in our evolutionary history.
"And that could mean in a sense that they are more important. So we need fear to be able to react appropriately do a dangerous situation, to run away; and also it's important in a situation of threat to warn those around us - who are likely family members and close friends - to warn them of the danger that we're facing."
Expressions of positive emotions, like achievement, tended to sound more different.
Sounding so different, it's not surprising that each group had a hard time identifying that and other sounds representing positive emotions. Sauter says it may be because positive emotions are more about creating and strengthening bonds within one's own group, so you might not want others to know about it.
"The exception to this is laughter, which seems to be something that we're prepared to share with strangers and friends alike, which I think is fairly reassuring, actually, that there are positive emotional signals that can communicate across all cultural boundaries."
We reached Disa Sauter at her current office at the Max Planck Institute in the Netherlands. She was at University College London when she did her research. It was published online by the Proceedings of the National Academy of Sciences, which also gave us permission to use the audio clips used in the study.