We often find ourselves laughing at the strangest of moments. As psychologists are discovering, those helpless giggles might be one of our most important and profound behaviours, says David Robson.

My conversation with Sophie Scott is nearly over when she spins round in her chair to show me a video of a near-naked man cannonballing into a frozen swimming pool. After a minute of flexing his muscles rather dramatically, he makes the jump – only to smash and tumble across the unbroken ice. The water may have remained solid, but it doesn’t take long for his friends to crack up.

“They start laughing as soon as they see there isn’t blood and bones everywhere,” says Scott. “And they are SCREAMING with mirth; it’s absolutely helpless.” (If you want to see the video in question, you can find it here – though it does contain some swearing.)

Why do we get such an attack of the giggles – even when someone is in pain? And why is it so contagious? As a neuroscientist at University College London, Scott has spent the last few years trying to answer these questions – and at TED2015 in Vancouver last week, she explained why laughter is one of our most important, and misunderstood, behaviours.

Scott’s work has not always met the approval of her straight-laced colleagues. She likes to point out a handwritten note she once found stuck to the top of her printouts. “This pile of paper seems like rubbish (because of the nature of the material) and will be disposed of if not collected,” the note read. “Is this science?” In an ironic nod to the criticisms, Scott is now wearing a T-shirt emblazoned with the question, ready for a comedy gig she is hosting later in the evening.

She started out her career by examining the voice more generally, and the rich information it offers about our identity. “You can get a good shot at my gender, my age, my socioeconomic status, my geographical origins, my mood, my health, and even things to do with interactions,” she says.

One of her experiments involved scanning professional impersonator Duncan Wisbey to explore the way that he comes to adopt the subtle mannerisms of other people’s speech (see video, below). Surprisingly, she found that the brain activity seemed to reflect areas normally associated with bodily motion and visualisation – as he, almost literally, tried to work his way under the skin of a character. More generally, the work on impersonations has helped her pin down the regions involved in things like accent and articulation – important aspects of our vocal identity.

But it was a study in Namibia that made Scott begin to realise laughter is one of our richest vocal tics. Previous research had shown that we can all recognise six universal emotions across cultures – fear, anger, surprise, disgust, sadness, happiness – based on facial expressions. Scott, however, wanted to see if we encode more subtle information in our voice. So she asked indigenous Namibians and English people to listen to recordings of each other and rate the emotions represented – including the six accepted universals, as well as relief, triumph, or contentment.

Laughter was the most easily recognisable emotion across both groups. “Almost immediately, it started to look different from the other positive emotions,” she says.

The more she probed, the more she became fascinated by its intricacies. For instance, she soon found out that the vast majority of laughs have nothing to do with humour. “People genuinely think they are mostly laughing at other people’s jokes, but within a conversation, the person who laughs most at any one time is the person who is talking,” she says. Instead, she now sees laughter as a “social emotion” that brings us together and helps us to bond, whether or not something is actually funny. “When you laugh with people, you show them that you like them, you agree with them, or that you are in same group as them,” she says. “Laughter is an index of the strength of a relationship.”

Infectious giggles

That might explain why couples can roll about laughing at each other’s apparent wit – while onlookers fail to be infected. “You’ll hear someone say ‘he’s got a great sense of humour and I really fancy him because of it’.  What you mean is ‘I fancy him and I show him I like him by laughing when I’m around him.’”

Indeed, mirth might be the primary way of maintaining relationships; she points to research, for instance, showing that couples who laugh with each other find it much easier to dissipate tension after a stressful event – and overall, they are likely to stay together for longer. Other recent studies have shown that people who laugh together at funny videos are also more likely to open up about personal information – paving more common ground between people.

Even the hilarity at the German man falling in the frozen swimming pool may have united the friends. “It’s interesting how quickly his friends start laughing – I think it’s to make him feel better,” says Scott. Along these lines, Robin Dunbar at the University of Oxford has found that laughter correlates with increased pain threshold, perhaps by encouraging the release of endorphins – chemicals that should also improve social bonding.

Scott is now interested in picking apart the differences between the “posed” giggles we might use to pepper our conversation – and the absolutely involuntary fits that can destroy a TV or radio broadcast, like this:

For instance, she found that the less authentic tones are often more nasal – whereas our helpless, involuntary belly laughs never come through the nose.

Her fMRI scans, meanwhile, have looked at the way the brain responds to each kind of laughter. Both seem to tickle the brain’s mirror regions – the areas that tend to mimic other’s actions. These areas will light up whether I see you kicking a ball, or if I kick it myself, for instance – and it could be this neural mimicry that makes laughter so contagious. “You are 30 times more likely to laugh if you’re with someone else,” she says. An important difference, however, is that the less spontaneous, social laughs, tend to trigger greater activity in areas associated with “mentalising” and working out other people’s motives – perhaps because we want to understand why they are faking it.

You may think it is easy to tell the difference between involuntary and more artificial laughs, but Scott thinks the skill develops slowly across the lifespan and may not peak until our late 30s. For this reason, she has recently set up an experiment at London’s Science Museum, where her team will be asking visitors of different ages to judge the authenticity of different clips of people laughing and crying. After all, she points out that crying is an infant’s primary way of communicating, whereas laughter gains more importance the older we get.

Although we may tend to dislike certain people’s “fake” laughs, Scott thinks it probably says more about us, and the way we are responding to their social signals, than anything particularly irritating about them. She tells me about an acquaintance who had frequently irritated her with a persistent, fluting, laugh. “I always thought that she laughed so inappropriately, but when I paid more attention to it I saw that what was odd was simply the fact I didn’t join in. Her laughter was entirely normal.” If she hadn’t disliked the person already, she says, she would have laughed away and wouldn’t have even noticed.

Why not listen to some of Scott's clips and judge your own abilities to read people’s laughter:

Beside probing the bonds in our closest relationships, Scott’s curiosity has also taken her to comedy clubs. “What’s interesting about laughter in the situation of stand-up is that it’s still an interaction,” she says. In a way, the audience is having a conversation with the comedian. “I’m interested in what happens when the audience starts laughing and how it dies away – whether are you in sync with people around you or whether you don’t care, because the experience is just between you and the person on the stage.”

Paradoxically, she says, comedians often find it easier to work in large venues, perhaps because the contagious nature of laughter means that waves of mirth can catch on more easily when there are more people. She recalls a video of comedian Sean Lock reducing the audience to fits of hysterics simply by saying the word “cummerbund” occasionally, thanks to the infectious laughter spreading through the audience.

So far, she has tried to equip audience members watching comedians with sensors to track the outbreak of laughter, with limited success – the audience froze under the attention. But she hopes to continue the work with a high-profile comedian like Rob Delaney, who may be able to break through the awkwardness.

Scott occasionally takes up the microphone herself at comedy nights in London, and I ask her if her insights have fed her stage persona?  She disagrees that science has offered her a fast track to comic genius, though as I discover at a charity gig the following evening, she is very funny.

As her “Is this science?” T-shirt reminds us, her more uptight colleagues might disapprove of her flippant attitude – but then, Scott understands just how powerful a tool that laughter can be to express ourselves, and get people to listen. “Laughter seems trivial, ephemeral, pointless,” she says. “But it is never neutral – there’s always a meaning to it.”

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Laughter increases the pain threshold and may send endorphins shooting through our veins.