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 the laughter is doing a lot of that emotional work for you.
Something that Robert Provine has pointed out, as you can see here, and in fact, the reason why we were laughing when we heard those funny laughs at the start, and why I was laughing when I found my parents laughing, is that it’s an enormously behaviorally contagious effect. You can catch laughter from somebody else, and you are more likely to catch laughter off somebody else if you know them. So it’s still modulated by this social context. You have to put humor to one side and think about the social meaning of laughter because that’s where its origins lie.
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, like my parents lying on the floor screaming about a silly song, 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 behavior somebody is doing as part of their communicative act to you, part of their interaction with you; they are choosing to do this.
In our evolution, we have developed two different ways of vocalizing. Involuntary vocalizations are part of an older system than the more voluntary vocalizations like the speech I’m doing now. So we might imagine that laughter might actually have two different roots.
So I’ve been looking at this in more detail. 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 imagine your friend told a joke, and you’re laughing because you like your friend, but not really because 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?
What does that sound like to you?
Posed? Posed. How about this one?
I’m the best. Not really. No, 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 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. Interestingly, you see something quite similar with chimpanzees. Chimpanzees laugh differently if they’re being tickled than if they’re playing with each other, and we might be seeing something like that here, involuntary laughter, tickling laughter, being different from social laughter. They’re acoustically very different.
The real laughs are longer. They’re higher in pitch. When you start laughing hard, you start squeezing air out from your lungs under much higher pressures than you could ever produce voluntarily. For example, I could never pitch my voice that high to sing. Also, you start to get these sort of contractions and weird whistling sounds, all of which mean that real laughter is extremely easy, or feels extremely easy to spot.
In contrast, posed laughter, we might think it sounds a bit fake. Actually, it’s not, it’s actually an important social cue. We use it a lot, we’re choosing to laugh in a lot of situations, and it seems to be its own thing. So, for example, you find nasality in posed laughter, that kind of “ha ha ha ha ha” sound that you never get, you could not do, if you were laughing involuntarily. So they do seem to be genuinely these two different sorts of things.
We took it into the scanner to see how brains respond when you hear laughter. And when you do this, this is a really boring experiment. We just played people real and posed laughs. We didn’t tell them it was a study on laughter. We put other sounds in there to distract them, and all they’re doing is lying listening to sounds. We don’t tell them to do anything.
Nonetheless, when you hear real laughter and when you hear posed laughter, the brains are responding completely differently, significantly differently. What you see in the regions in blue, which lies in auditory cortex, are the brain areas that respond more to the real laughs, and what 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 with greater auditory processing of these novel sounds.
In contrast, when you hear somebody laughing in a posed way, what you see are these regions in pink, 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, “A ha ha ha ha ha,” you’re trying to work out why they’re laughing. Laughter is always meaningful. You are always trying to understand it in context, even if, as far as you are concerned, at that point in time, it has not necessarily anything to do with you, you still want to know why those people are laughing.