Why do we laugh?

The Brainstorm Long Read: everyone likes a good laugh but what actually causes us to chuckle in the first place and why?

By Luke O'Neill, Trinity College Dublin

Humans laugh. A lot. Compared to other species, even the chimp and the supposed champion in the laughter league, the hyena, we are tops when it comes to laughing. Everyone likes a good laugh. But why do we laugh? Why do we find some things funny? What is the funniest joke ever? Why is most laughter not actually about finding something funny but rather fulfils a social function? And what happens when we ‘corpse’, or get a completely inappropriate fit of the giggles? The danger here is, as someone once said, that ‘Trying to explain why something is funny is somewhat akin to dissecting a frog. Nobody laughs and the frog dies.’ Still, we must be brave. Science knows no boundaries, and as long as you get a laugh out of it we’ll be fine.

A good place to start is to consider what happens to our bodies when we laugh. In what is known as mirthful laughter, the type where our bellies vibrate, the muscles in our rib cage start to produce large contractions, which leads to air being squeezed out of our bodies – creating the sound of the laugh. When the contractions run close together, we emit a high-pitched wheeze. In contrast, the more social laughter that arises when we talk to someone doesn’t involve these bodily changes.

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From RTÉ Radio One's History Show, Luke O'Neill discusses his new book Humanology

That distinction is important when studying the purpose of laughter. One of the most telling experiments done to examine the function of laughter involved 33 women. These women watched a humorous movie (in this case, perhaps inevitably, it was When Harry Met Sally). To measure how much they laughed they each had monitors put on their abdomens to measure their bellies moving. Why was this important? The scientists were interested in measuring mirthful laughter. This can be defined as real laughter – a belly laugh. They also watched a movie that wasn’t funny (or at least not intentionally): a tourist video (luckily they weren’t shown a video from Fáilte Ireland, as they might have laughed all the way through).

Watching When Harry Met Sally resulted in an average of 30 belly laughs per woman. The tourist video gave one belly laugh per woman on average. The scientists also took blood samples and looked at the immune systems of the women. The measure here was of a cell type called natural killer (NK) cells. These cells are important for fighting viruses. And guess what? After watching When Harry Met Sally the NK cell activity was enhanced, indicating a boost in the immune system. One effect of laughter therefore could be to make our immune systems work better. Perhaps it’s a good idea for your doctor to prescribe you two tickets to see Dara Ó Briain.

Laughter can lower your blood pressure and increase blood flow to your heart. It is therefore a powerful ally in the fight against heart disease

Many previous studies had shown that negative emotions and stress can have a negative impact on the immune system. This is down to a stress hormone called cortisol, which is elevated when we are anxious or worried. High levels of cortisol have the negative effect of depressing our immune systems. In another study the scientists examined a section of the brain just behind your forehead called the prefrontal cortex, a brain region whose activity correlates with depression. If you have more activity on the right-hand side of this region you are inclined to be a ‘glass half empty’ kind of person. If the left-hand side is active, then you are ‘glass half full’.

This is useful, because scientists can then categorise people into optimists or pessimists without having to resort to questionnaires, which can be unreliable. And they got a very striking result. Those with a more positive disposition (the ones whose glass is always half full) had a four times stronger response to a flu vaccine than those who were glass half empty. This study provided compelling evidence that those who are inclined to positivity are likely to suffer less from colds and us. One problem with this study is cause and effect. Maybe the fact that they were sick less often resulted in them having a more positive outlook, as reflected in the left-hand side of their prefrontal cortex being more active.

From RTÉ Radio One's Ray D'Arcy Show, an interview with cognitive neuroscientist Sophie Scott who studies laughter

Either way, all of this suggests that good humour and laughter may well be the best medicine. And there are other health benefits to having a good laugh. Laughter can lower your blood pressure and increase blood flow to your heart. It is therefore a powerful ally in the fight against heart disease. It also turns out that it’s actually a form of exercise. When you go to the gym don’t be afraid to laugh at that middle-aged man in Lycra and a sweatband. In one study, laughing 100 times was the equivalent of 10 minutes on a rowing machine or 15 minutes cycling. And a lot more fun.

Laughing can also lower your blood sugar levels, which is a good thing, as this will impact on your risk of developing type 2 diabetes. This type of diabetes makes you resistant to your own insulin – which means that your cells can’t take up as much glucose, and so your blood glucose level is too high, causing all kinds of health problems. In one study, people with type 2 diabetes ate a meal and then attended a boring lecture. The next day they had the same meal but this time went to a comedy show. Scientists measured the participants’ blood glucose in both situations, and found that having a good laugh at the comedy show meant that blood sugar levels didn’t rise after the meal as much as they did after the boring lecture. One possible reason is that the participants, muscles burned the glucose through laughing, but whatever the interpretation, there was a clear benefit. And then there’s the effect laughter has on pain sensation (which is lowered), the easing of fear and anxiety being clear evidence that it helps us deal with bad situations.

Scientists are of the opinion that laughter allows humans to connect, bond and communicate with one another

But perhaps the most convincing work that has been done on laughter looks at its role in social bonding. We all know that laughter is contagious. Have you ever caught a laugh from someone else simply because they are laughing and not because of what they are laughing at? And one bout of laughter will set us up to laugh again – this is why comedy shows have a warm-up comedian: once we start to laugh we are inclined to keep laughing. In a study at a shopping mall, scientists examined people laughing, eavesdropping on conversations. They then figured out the cause of the laughter. Strikingly, 80 percent of laughter wasn’t because of jokes or humorous anecdotes. Laughter was happening because of social interaction. Watch out for this next time you are with people: often your laughter is not at something funny, but rather is saying, I’m friendly, you don’t need to fear me, please keep talking to me!

Scientists are of the opinion that laughter allows humans to connect, bond and communicate with one another. The more relaxed you feel with someone, the easier it is to laugh. People are 30 times more likely to laugh in a social setting than if they are alone. This will be obvious to us all. When we watch a comedian on TV on our own, we rarely laugh. But watch a comedian with other people and we can’t stop laughing. Laughter in that situation is a form of social bonding. As the great comedian Victor Borges said, ‘Laugher is the shortest distance between two people.’

From RTÉ Archives, a comedy sketch from The Likes of Mike in 1972 featuring a day in the life of presenter Mike Murphy

Laughter also boosts your interpersonal skills. It’s true what they say: when you laugh the world laughs with you, but when you weep, you weep alone. People are less likely to hang out with others who have nothing positive to say, so finding humour will improve your social skills. Laughter can also be about who is the most powerful in a group. One study examined laughter in work meetings. It was easy to figure out who the boss was, because that person was more likely to generate laughter in the group. The plebs were inclined to laugh, indicating ‘I know you’re the alpha person here, please don’t kill me (or re me).’ So laughter can have a function indicating status.

This leads us to one of the great unsolved mysteries in human psychology – why are some things funny? What makes a good joke? Again, we’re reminded of the dissected frog, so we must proceed with caution. The earliest recorded joke is from 1900 BC. It is a saying of the Sumerians, who lived in what is now southern Iraq, and it goes: ‘Something which has never occurred since time immemorial; a young woman did not fart in her husband’s lap.’ Toilet humour. Funny back then, and still funny now.

The couple that laughs together stays together. It’s an indicator of emotional support, closeness and high regard

The second-oldest joke dates to 1600 BC, and is a riddle found in the tomb of Pharaoh Snefru, who lived over 4,000 years ago. Egyptologists reckon it was written by a disgruntled architect. The joke was ‘How do you entertain a bored pharaoh? You sail a boat down the Nile full of young women dressed only in fishing nets, and invite him to go and catch a fish.’ This is a rather complex joke, it has to be said (as in, Do you get it? Because I don’t). But one thing it has in common with our times is it is poking fun at authority, which is always fun. Along with toilet humour, this is a second category of joke. Ah, scientists, for ever trying to classify things. The other main category pertains to unexpected happenings in a story. Your mind is heading in one direction, but then the punchline takes you somewhere else, and for some reason the mind slip leads to a response that we call humour.

A few years ago there was a scientific attempt to find the world’s funniest joke, and it had that characteristic. Thousands of jokes were sent in and these were rated by 1.5 million people, with one joke emerging as the winner. You want to hear the joke, don’t you? Well here it is. Two guys go on a hunting trip. One of them collapses, not breathing, skin turning blue. The other guy calls emergency services and says ‘You’ve got to help me! My friend has collapsed and appears to be dead.’ The emergency services say, ‘Calm down. We can help. First, let’s make sure he’s dead.’ There’s silence, followed by a gun shot. The guy gets back on the line and says ‘OK, What now?’ The comedy writer Spike Milligan gets the credit for writing that joke in 1951, for a radio programme called The Goon Show.

From RTÉ Archives, Spike Milligan on The Gay Byrne show on RTÉ Radio One in 1982

What is it that makes that joke funny? Well, Sigmund Freud had something to say about that. In his book Jokes and Their Relation to the Unconscious he argued that humour can be a way to relieve tension. Freud speculated that humour is a safety catch for the expression of repressed sexual feelings (inevitably), or feelings of fear, hostility or unease. The above joke sets up an uneasy situation, involving a man and his dying friend, and then relieves the tension by turning it into an absurd situation. This is now known as the ‘tension-relief theory’. Humour provides emotional arousal (usually in a story) with signals of safety – the recognition that the threat isn’t real, that it’s all ‘just for fun’.

We can see the different types of humour in the development of children, who generate humour from a very early age. To begin with it’s in things like peekaboo and funny body movements (falling and sticking legs in the air is hilarious to a one-year-old). By the age of three, children will use objects in unexpected ways – putting underpants on their heads, for example. Early jokes will be influenced by their parents but will become increasingly original. But they begin by displaying the social function of humour: smiling, laughing and looking to their parents for a reaction.

A man doesn’t tend to care if the woman is funny as long as she finds him funny

Once we reach adulthood, we realise that humour can be useful to attract a mate, and perhaps this is a key reason why it evolved. For men in particular, it is a thought of as a way of showing off intelligence and good genes. If a man is humorous, he must have good genes that give him that intelligence and status. We also judge people we are attracted to as being funny, and funniness enhances attractiveness. A French study (inevitably this was done in France) found that a woman was three times more likely to give a man their phone number if the man had just told a joke to his friends. It’s a mystery how that study was done, as there is no record of French men ever telling jokes (apparently).

A study in the US concluded that women want men to have a GSOH (great sense of humour, for those of us unused to dating acronyms), but also to be receptive to her jokes. A man doesn’t tend to care if the woman is funny as long as she finds him funny. There is therefore some evidence that the production of humour is more of a male trait (at least in live performance), whereas receptiveness to humour is common to both men and women. Studies show that men are inclined to enjoy toilet humour, slapstick and competitive themes, whereas women favour nonsense jokes and clever word play. And one thing both genders like is gallows humour – making a joke in the wake of something bad, or in anticipation of it. This seems to serve a cathartic function, allowing people to distance themselves from a difficult and upsetting situation. It is also used for social cohesion, especially among soldiers, undertakers and surgeons.

And then, once you find a mate, guess what? Studies into couples and how good their relationships are have revealed that a major indicator is couples laughing with each other. The couple that laughs together stays together. It’s an indicator of emotional support, closeness and high regard. Of course there is a chicken-and-egg problem with this. Do we laugh first, and does that make us closer? Or are we close to begin with, and then we laugh more? Either way it’s a very good sign.

This is an extract from Professor Luke O'Neill's Humanology: A Scientists's Guide To Our Amazing Existence (Gill Books, priced €24.99). Professor Luke O'Neill is professor of biochemistry in the School of Biochemistry and Immunology at Trinity College Dublin

The views expressed here are those of the author and do not represent or reflect the views of RTÉ

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