Scientists say we can tell if people are friends just by listening to them laughing together

Friends for sure.
Friends for sure.
Image: a4gpa/Flickr, CC BY-SA 2.0
We may earn a commission from links on this page.

Imagine going to a networking event where no one is faking interest in one other. That’s essentially what socialization was like for our primitive ancestors, for whom laughter was both a sign of familiarity and an involuntary gesture.

Along with the ability to speak, modern humans have evolved the ability to fake laughter by voluntarily vibrating our vocal chords. This allows us to do things like laugh at the jokes of people we’ve just met, even if they aren’t funny.

Our polite laughter isn’t fooling as many people as we may think, according to a recent study published in PNAS by researchers from the University of California at Los Angeles. The study found that the majority of listeners could tell if pairs of people were strangers or friends from a one second recording of their laughter.

The researchers played audio clips of different pairs of English-speakers laughing to 966 listeners from 24 different places around the world. The clips contained the laughter of six pairings of people who differed by gender and familiarity: two female friends, two female strangers, two male friends, two male strangers, one male and one female friend, and one male and one female stranger.

Then the researchers asked the listeners a question: “Do you think these people laughing were friends or strangers?”

Listeners were able to determine whether the laughers in a clip were friends or strangers correctly 61% of the time. Overall, there was a tendency to judge female pairs as friends and to judge male pairs as strangers. Additionally, the researchers found that female listeners were better at correctly judging the relationships of all of the pairs. 

Listen to the recordings below and see if you can tell which pairs are friends and which are strangers.


Sample 1 — male strangers
Sample 2 — female strangers
Sample 3 — male friends
Sample 4 — female friends
Sample 5 — male/female friends
Sample 6 — male/female strangers