Why Laughter Is Contagious: Got The Giggles? Blame Evolution

Sitting in the audience at a stand-up show; watching a comedy at the movies; at the office party when your boss breaks out their best knock-knock joke: these are all places where laughter is both encouraged and expected. During a quiet moment in church? Not so much. But wherever you are, if you hear someone else laughing, it’s likely you’ll get the urge to giggle too – however inappropriate that may be! Should we all just be able to control ourselves better, or is laughter really contagious?

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The answer, in short, is yes.

“All emotions are contagious”

“Is laughter contagious? Well, actually, all emotions are contagious,” Dr Sandi Mann, chartered member of the British Psychological Society, told IFLScience. “We are designed to pick up other people’s emotions.”

It’s part of our evolution, and it’s something we share with other mammals. It’s been well established that apes – our closest relatives – laugh in a remarkably humanlike way. If you’re ever close enough to a bonobo to try tickling it (not something we’d necessarily recommend), you’ll find out.

Recent research even found that apes may have a sense of humor and love to tease each other. A 2021 review concluded that 65 different animal species show evidence of “play vocalizations” that mimic humans laughing when we’re having fun, mostly mammals but a few birds as well. 

In fact, laughter is such a fundamental part of what it means to be human that it transcends language and culture – there’s not a single community of people on Earth that we know of who don’t laugh. 

Why laughter is good for us

Part of the reason why a fit of the giggles spreads so easily, Dr Mann told us, is that shared emotions are integral to social bonding. A 2022 paper from University of Oxford Emeritus Professor of Evolutionary Psychology Robin Dunbar explored this further. 

Humans laugh together all the time, but we’re rarely seen picking lice out of each other’s hair these days.

“I suggest that, when hominins needed to increase the size of their groups beyond the limit that could be bonded by grooming, they co-opted laughter […] as a form of chorusing to fill the gap,” Dunbar wrote. 

Grooming – a social behavior we particularly associate with monkeys and apes, but which is seen throughout the animal world – boosts the production of endorphins in the brain. These chemical messengers relieve pain and generally make us feel good. Dunbar detailed some evidence that laughter has a similar effect, with the added benefit of being less intimate and time-consuming than grooming. Hence, humans laugh together all the time, but we’re rarely seen picking lice out of each other’s hair these days. 

A hit of endorphins also helps us de-stress. When a group of people are sharing a tense situation, Dr Mann told IFLScience, humor can help to alleviate that as well as strengthen the bond between them: “Sometimes we just need to smile, laugh, have fun to relieve the stress.”

You might have heard people talk about using “gallows humor” as a coping strategy – it’s common among those whose jobs regularly expose them to distressing scenarios. 

“Medical and emergency services personnel are particularly likely to use humour to counteract the effects of dealing with stressful situations and this contributes to a person’s resilience when dealing with stressful situations,” wrote Sarah Christopher, then a senior lecturer in paramedic practice at Sheffield Hallam University, in a 2015 paper. 

As Christopher explained, this has been true even in the darkest chapters of human history, things about which most people would dare not crack a joke. The paper includes a number of examples of Holocaust survivors explaining how humor helped them to keep up their morale. 

In medical scenarios, it’s not only the staff but the patients who can benefit from a dose of laughter – as we mentioned before, it has pain- and stress-relieving powers. 

When we talk about the benefits of sharing a laugh, one study of clinician-patient interactions in five Australian emergency departments contains a particularly illustrative example. In general, the authors found that laughter was a surprisingly common feature of a visit to the ER, but one patient named “Janet” took the cake, recording 38 instances of laughter during her 6.5-hour stint.

Transcripts of conversations show how Janet’s attempts at humor went largely unreciprocated by the attending physician – and even just reading them, you can feel yourself cringe. There’s a personality mismatch there. It’s all a bit awkward. 

Things couldn’t be more different with one of the nurses who took care of Janet. While taking a blood sample, she shared in Janet’s jokes, and they laughed together. This response “may […] serve to distract the patient from the potential unpleasantness of the immediate task, as well as Janet’s more general discomfort with being a patient,” the authors wrote. 

While not everyone responds in the same way to dark humor, here the shared joke helped Janet and this nurse to find some common ground and, we can speculate, made an unpleasant situation a little bit easier to bear.

The many flavors of human laughter

Unsurprisingly, particularly for newly minted healthcare workers, the prevalence of gallows humor in these kinds of settings can come “as something of a culture shock”, Christopher wrote. But we humans are a many-layered bunch, and beyond your garden variety “fun”, there are actually lots of situations that can get us chortling together.

Some things are quite spontaneous, and you have to kind of ‘be there’ to find it funny. Other things that we laugh at are when things are incongruous. 

Dr Sandi Mann 

“What makes us laugh is an interesting phenomenon,” Dr Mann told IFLScience. “There’s a whole range of different categories that make us laugh. Some things are quite spontaneous, and you have to kind of ‘be there’ to find it funny. Other things that we laugh at are when things are incongruous.” 

Like the church example we mentioned earlier, sometimes people laugh at times they probably shouldn’t, such as just after receiving some bad news. But Dr Mann said that in those situations, people shouldn’t be too hard on themselves: “They feel awful about it, but it’s really just a stress-reducer.”

There are also the classics of laughing at ourselves – something of a national sport for the British – and laughing at the misfortune of others, what the Germans call schadenfreude. That last one is so universally relatable that there’s an entire number dedicated to it in the musical Avenue Q. Side note: if any psychologists out there are looking to observe the contagious effect of laughter in real-time, you could do worse than sitting a bunch of people down to watch that show!

Well-placed humor could be the difference between getting a job and getting rejected, or could secure you a second date. A joke might break the ice or spark a bond between people who weren’t getting along. In fact, the study of humor, which has sometimes been neglected in psychology, can open up a window into lots of aspects of human character. 

More and more, what we’re realizing is that humans need to laugh together. A brief chuckle is almost a form of punctuation, so ubiquitous that we don’t consciously notice it – but as Dunbar wrote, “[C]onversations that lack laughter quickly become hard work.” 

Laughter – like many other expressions of human emotion – is definitely contagious. But unlike athlete’s foot or measles, this is one contagion you actually want to spread around. 

 This article first appeared in Issue 29 of our digital magazine CURIOUS. Subscribe and never miss an issue.