Better think twice the next time you fake a laugh—your breathing could be the giveaway that blows your cover, new research suggests.  

A study conducted at the University of California, Los Angeles (UCLA) shows that the subtle breathing patterns of forced laughter tip off listeners to our feigned, if well-meaning, chuckles.

The study, published in Evolution and Human Behavior, explains what makes the phenomenon of human laughter so unique, and why it’s so hard to fake.

Many Animals Laugh

Our ability to laugh is shared by many animals, such as gorillas and even rats, but it’s the apparatus humans use to force laughter that separates us from other giggling creatures. 

“It’s a vocalization that we share with many other animals, and it’s so prevalent in human interaction that I’ve always been interested in how it functions with people,” said Greg Bryant, study author and an associate professor of communication studies at UCLA.

In the first scholarly research of its kind, Bryant focused specifically on the differences between genuine and forced laughter in humans.

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What’s in a Laugh?

Fake and real laughs are not only the products of different social situations, they also come from different vocal systems. The speech system unique to humans allows us to force a chuckle—even if a joke is terrible. A true, hearty laugh, on the other hand, is uttered using the emotional vocal system that we share with primates.

The difference is apparent in the breathing patterns that are produced by these different vocal systems. During a real laugh from the emotional vocal system, the windpipe opens and closes rapidly—much more quickly than we can open and close it consciously when we force a laugh using the speech system. People who hear us laugh pick up on these changes in breathing and are able to recognize that they don’t correspond to what we know as the sound of a real laugh.

Researchers conducted three experiments using real laughter from recordings of random conversations between college roommates. They then matched these recordings with the faked laughter of 18 other UCLA students to identify acoustic differences between the real and fake laughter.

In the first experiment, researchers asked students to discern between the real and fake laughter, and about two-thirds of them were able to detect the phony laughs. The next experiment proved more difficult. When researchers sped up the fake laughs to make them sound more realistic, about half of the students could not tell the difference between real and fake amusement.

In the third experiment, researchers drastically slowed down the recordings and asked the students whether the sounds came from human or non-human animals. Students were stumped as to who or what created the real laugh sounds, but they could tell that the fake laughs were emitted by humans.

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Fake It Till You Make It?

So, is it possible to tell if a friend secretly dreads your go-to one-liner? The results show that our acute breathing patterns can make for a dead giveaway. We naturally understand, almost from birth, what constitutes a real laugh, and laughs that don’t fall within that internalized framework don’t cut it.

You can always try, though, by mimicking the facial and physical movements typical of being in on a truly good joke.

Past research has shown that laughing releases the hormone oxytocin, which promotes social bonding. Being able to tell the difference between real and fake laughter is an evolutionary advantage, if you don't want to be taken for a ride by someone you thought was an ally.

Bryant says he's more interested in the basic biology of the research than its practical applications, but he says his study of laughter does offer a deeper understanding of our relationship with fellow animals.

“Even though people seem so unique, and we are unique in many ways, we have a lot of everyday behaviors that are very much like non-human animals,” Bryant said. “The next time you hear someone laughing, you can think of it as an animal call.”

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