Sophie Scott: Why Is Laughter Contagious? Neuroscientist Sophie Scott studies laughter, specifically its effect on our body and brain. She discusses laughter's contagious nature, as well as its role in maintaining social bonds.

Why Is Laughter Contagious?

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GUY RAZ, HOST:

It's the TED Radio Hour from NPR. I'm Guy Raz. So a few weeks ago, we were talking with a research scientist named Sophie Scott.

SOPHIE SCOTT: Hi, speaking.

RAZ: Sophie works in London...

SCOTT: Are we live or is this recorded?

RAZ: ...And we were recording, of course.

SCOTT: Fantastic. Just thought I'd check.

RAZ: It would be crazy if it was live - and now let's take your calls for Sophie Scott.

SCOTT: (Laughter).

RAZ: Let's open up the lines.

SCOTT: (Laughter).

RAZ: OK, now, that sound...

SCOTT: (Laughter).

RAZ: What happens to your brain when you hear that is exactly what Sophie studies as a cognitive neuroscientist.

SCOTT: So I study - I study human brains, but I'm interested in what we're doing right now. You know, we can't see each other but we are having, you know, perfectly fluent conversation.

RAZ: Yeah, right.

SCOTT: And I'm interested in how that goes on in terms of perception and production. And I'm interested in the verbal stuff that we do and also in the other noises we make with our mouths.

RAZ: And one noise in particular that Sophie focuses on is laughter and why like a cold or even a yawn, there's something contagious about.

SCOTT: So yawning is very like laughter in this respect. You can catch it from somebody, and you're much more likely to catch it from somebody you know than someone you don't know.

RAZ: OK, so to set this up a little bit more, you might remember this viral video that went around a couple years back.

SCOTT: Is this where somebody starts to laugh when a woman's reading something on her phone?

RAZ: Right. Basically, this was an improv group in Berlin and they filmed a stunt on the Metro train there. One lady is looking at her phone and she sees something funny, so she shows it to a friend and they start laughing.

(SOUNDBITE OF VIDEO)

UNIDENTIFIED PEOPLE: (Laughter).

RAZ: (Laughter) And then somebody else around her starts laughing.

(SOUNDBITE OF VIDEO)

UNIDENTIFIED PEOPLE: (Laughter).

SCOTT: It's lovely (laughter).

RAZ: This is a packed train. Now, Germans are not - you know, they're kind of serious. They're, like, reading their papers.

SCOTT: (Laughter) They're not hilarious fins, yeah.

RAZ: Slowly but surely, even though the rest of the passengers can't see the first woman's phone and don't know what she's laughing at, the laughter spreads and spreads.

(SOUNDBITE OF VIDEO)

UNIDENTIFIED PEOPLE: (Laughter).

RAZ: And Sophie says even though the initial spark of laughter was staged and planned, the spread...

(SOUNDBITE OF VIDEO)

UNIDENTIFIED PEOPLE: (Laughter).

RAZ: ...That was real.

SCOTT: You can go from very staged laughter, very polite laughter, very social laughter through to genuinely helpless, involuntary laughter along that same route 'cause laughter just primes laughter. If you look at anywhere in the world where if you want people to laugh...

(SOUNDBITE OF VIDEO)

UNIDENTIFIED PEOPLE: (Laughter).

SCOTT: ...You get them laughing and then you keep them going.

RAZ: And this part, cognitive neuroscientists like Sophie Scott, they understand it pretty well - laughter, it spreads. But what we understand less is why. Here's Sophie on the TED stage.

(SOUNDBITE OF TED TALK)

SCOTT: I'm going to talk to you today about laughter. And in terms of the science of laughter, there isn't very much. But there's - it does turn out that pretty much everything we think we know about laughter is wrong. So it's not at all unusual, for example, to hear people say humans are the only animals that laugh. Nature thought, oh, humans are the only animals that laugh. In fact, you find laughter throughout the mammals as being well described and well observed in primates, but you also see it in rats. And wherever you find it - humans, primates, rats - you find it associated with things like tickling, and that's the same for humans. You find it associated with play, and all mammals play. And wherever you find it, it's associated with interactions. So Robert Provine, who's done a lot of work on this, has pointed out that you are 30 times more likely to laugh if you are with somebody else than if you're on your own. And where you find most laughter is in social interactions like conversation. So if you ask human beings when do you laugh, they'll talk about comedy and they'll talk about humor, and they'll talk about jokes. If you look at when they laugh, they're laughing with their friends. And when we laugh with people, we're hardly ever actually laughing at jokes. You are laughing to show people that you understand them, that you agree with them, that you're part of the same group as them. You're laughing to show that you like them. You might even love them. You're doing all that at the same time as talking to them. And in fact, the laughter is doing a lot of that emotional work for you.

RAZ: It's the kind of laughter you experience maybe late at night when you're a little slaphappy with your friends because that kind of laughter, the kind of laughter we heard on that train in Berlin...

(SOUNDBITE OF VIDEO)

UNIDENTIFIED PEOPLE: (Laughter).

RAZ: ...It's just another way we have of saying...

>>SCOTT I know you. I like you.

RAZ: Yeah.

SCOTT: I've got something in common with you. I want to hang out with you. A lot of this sort of mirroring of other people's behavior like you're guessing - behavioral contagion. It's always got a positive meaning. And in fact, if you look within conversations, you and I will have started to breathe at the same time as soon as we started speaking. We didn't decide to do this. We just have to do it, actually, to have a conversation. We have to coordinate our breath. What you'll also find is the more you like the person you're talking to, the more you'll align other things as well. So you'll start to use the same words as them, you'll start to use the same grammatical structures as them.

RAZ: Oh, my God.

SCOTT: You don't do that if you don't like somebody, to put it perfectly honest. You do it when you like someone. You know, you kind of got that social link.

RAZ: On the show today, exploring those social links, How Things Spread - trying to understand how emotions, disease, even ideas themselves spread among us and tie us together. But first, back to Sophie Scott and a really interesting part of her research on laughter, which she presented on the TED stage.

(SOUNDBITE OF TED TALK)

SCOTT: Now, something I've got very interested in is different kinds of laughter. And we have some neurobiological evidence about how human beings vocalize that suggests there might be two kinds of laughs that we have. So it seems possible that the neurobiology for helpless, involuntary laughter might have a different basis to it than some of that more polite social laughter that you encounter, which isn't horrible laughter, but it's some of these behaviors somebody is doing as part of their communicative act to you - part of their interaction with you. They are sort of choosing to do this. So I've been looking at this in more detail. And to do this, we've had to make recordings of people laughing, and we've just had to do whatever it takes to make people laugh. And we got those same people to produce more posed social laughter. So instead, imagine your friend told a joke and you're laughing 'cause you like you friend but not, you know, not really 'cause the joke's all that. So I'm going to play you a couple of those. I want you to tell me if you think this laughter is real laughter or if you think it's posed. So is this involuntary laughter or more voluntary laughter?

(SOUNDBITE OF VIDEO)

SCOTT: (Laughter).

What does that sound like to you? Posed?

UNIDENTIFIED PEOPLE: Posed.

SCOTT: Posed. How about this one?

(SOUNDBITE OF VIDEO)

SCOTT: (Laughter).

I'm the best.

(LAUGHTER)

SCOTT: Now, that was helpless laughter. And in fact, to record that, all they had to do was record me watching one of my friends listening to something that I knew she wanted to laugh at. And I just started doing this. Now, what you find is that people are good at telling the difference between real and posed laughter. They seem to be different things to us. We took it into the scanner to see how brains respond when you hear laughter. And what it seems to be the case, when you hear somebody laughing involuntarily, you hear sounds you would never hear in any other context. It's very unambiguous. And it seems to be associated to be greater auditory processing of these novel sounds. In contrast, when you hear somebody laughing in a posed way, what you see are these regions which are occupying brain areas associated with mentalizing, thinking about what somebody else is thinking. And I think what that means is even if you're having your brain scanned, which is completely boring and not very interesting, when you hear somebody going (laughter), you're trying to work out where they're laughing.

RAZ: OK, so I get that laughter is always meaningful and that something's going on in the brain, right? But we don't really understand why it's contagious - right? - I mean, like, why it spreads.

SCOTT: No, no, and we know that it is, we know that it happens, we know that it is contagious - but clearly can't be the whole story. We know it's more complex than that. And we don't really understand, you know, (unintelligible) the time course. People always laugh at the end of sentences, for example, and they really coordinate their laughter very tightly to do that. So it's not just contagious, it's actually being really highly orchestrated. Whereas the timescale of spontaneous, helpless laughter can actually be quite slow. People can hear something that makes them start to laugh and then a few beats later, they start really laughing hard. And then they're lost to you for a few minutes.

(SOUNDBITE OF VIDEO)

UNIDENTIFIED PEOPLE: (Laughter).

SCOTT: It's a tiny little sort of dollop of the whole mammal behavior which does a huge amount of good helping you make even very transient social relationships go slightly better.

RAZ: Sophie Scott, she's a cognitive neuroscientist at University College London. You can see her entire talk at ted.com.

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