Want to know whether a group of individuals are close confidantes or mere acquaintances? Pay attention to their laughter. According to NPR, a new study published in the Proceedings of the National Academy of Sciences reveals that people from around the world can tell how close two humans are by listening to their shared guffaws.

In 2003, Gregory Bryant, a psychologist at University of California, Los Angeles, recorded college students of both sexes talking with each other. Some were friends; others were strangers. Recently, Bryant cut out one-second-long clips of the pairs laughing, and then he and his colleagues played them for 966 volunteers in 24 different societies across the world.

The listeners came from vastly different cultural backgrounds. Some were members of New Guinea's indigenous tribes, and others hailed from Peruvian villages, or cities in India and China. However, 61 percent of them could tell which college students were friends and which weren't—all from hearing a single second of laughter.

Turns out, when people laugh with friends, their chuckles are noticeably more excited—faster, irregular, and loud. People around the world can hear this difference, indicating that "laughing isn't necessarily just about communication between the people who are laughing, but potentially it might be a signal to outsiders that gives them some information," Bryant told Smithsonian. "A group of people laughing at a bar might be producing a chorus of signals to others without really being aware of it."

The study might help researchers learn more about how laughter served as a nonverbal communication behavior that contributed to the evolution of human societies. For instance, it might allow outsiders to listen to the members of a new group and quickly determine whether they're close or not.

[h/t NPR]