Did I inherit my laugh?

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1:16Caroline Steel:There's a set of twins who were raised separately and then brought together later in life and they met and one of the first things they did is laugh. The strange thing was, when we met, we just sort of said, oh, hello. As if we'd always known each other. And I think we even started laughing then. Well, we did. We did. And it turns out that their laughs are identical. Did you kiss and hug me? No. Did you say, oh, my beloved sister? No. This is Crowd Science from the BBC World Service. I'm Caroline Steele and this episode is all about having a laugh. Specifically about having someone in your family's laugh.

2:07Caroline Steel:All thanks to a question from the person behind this wonderful chortle. My name is Limby Kani. I'm from Lusaka, Zambia. And what's your question for CrowdScience? My question is, can the style in which someone laughed be inherited? For example, people often say that someone laughs like their dad. And I've been wondering, like, is that actually true? Can it be a genetic factor or is it purely environmental, like where they grew up? And when you say someone laughs like their dad, are you talking about anyone in particular? I have been told that I sometimes laugh like my dad, but I don't really believe it.

2:51I think I have my own distinct style of laughter.

2:55Caroline Steel:Interesting. Well, I guess let's hear what you and your dad sounded like.

3:06Caroline Steel:To me, Limbukhani and his father sound identical. So to try and understand why, it's quiz time. Would you say you're similar in other ways? Do you have a similar personality? Yeah, actually, there have been quite a few moments I've found myself sounding like my dad. It always throws me off, like, I'm becoming my dad. What about your upbringings? Did you have a sort of similar upbringing to your dad? No, no, no, no, no. Have you got, like, a similar height and build? I'm actually the tallest one in my family for some reason. And for some reason, I do have, like, a slightly different facial structure.

3:50Caroline Steel:Okay, so you had a different childhood from your dad. You don't think you look hugely similar, maybe a bit similar, and yet you've ended up with a similar laugh. You might not agree, but I'm judging it to be very similar. So that's interesting. Do you think you could have inherited it from his genetics, or do you think it's an environmental thing? I'm actually not sure. I think it might be both, right? OK, great. Well, we're going to have to chat to the scientists and find out. And yeah, get back to you. Yeah, I'll be looking forward for that. Good. That certainly put a smile on my face. Thank you, Limba Carney.

4:33Caroline Steel:And thanks to your dad, too. Laughs come in all shapes and sizes. From a wheeze to a guffaw, every laugh is unique. But where do they come from? Do we pick up our laugh from the world around us? or does laughter have a genetic component? Now that is a laugh I'd like to bottle. It belongs to Professor Sophie Scott at University College London in the UK, one of the world's leading experts in laughter. Hello! I love your purple suit, it's so cute. I'm going to wear a green shirt and my son just went, no, you'll look like the Joker! Now let's start with the basics. how do our bodies make the sounds that we recognize as laughter?

5:19What's happening is you start squeezing air out by contracting the muscles between your ribs. Ha ha ha ha ha.

5:27Caroline Steel:Yeah you're sort of forcing breath out. Exactly. Sounds like a horrible laugh. And that's squeezing air out through your voice box so you tend to make a sound there or sometimes it can just go and that's when this exhalations come so fast together they just go into a spasm sort of sound also you're forcing air out under much higher pressure than usual and that starts to give you higher pitches to your voice so i've got a really high pitch laugh i could never sing that high i'd love to be able to but i could not voluntarily get my voice up there and also if you've ever laughed you felt like you've got an ache at the back of your throat yes that's because that the pharynx that's the space but behind your tongue behind the back of your throat that starts tightening up so you're squeezing out more air under higher pressure through a narrower pipe and that means you get again these high pitches but you also start getting these squeaks and whistles your body's desperate to try and get some air to come back in and sometimes you can hear people gasping for breath and so quite often that makes a sound you know so you get those sorts of gasps happening as well it's a world of peculiar sounds you can even get what's called a glottal whistle, where you set up such a high pressure around the voice box that you start getting a distinct whistling sound.

6:41And that's very, very hard to fake.

6:45Caroline Steel:Laughter is an incredibly physical process. It involves much more of the body than I expected. Laughter is more like a different way of breathing. And it's more like an animal call than it is like speech. So when we speak, we take a breath in and then we produce a very finely controlled flow of air out through our larynx our voice box where we produce like the pitch and the rhythm and the melody of the voice just it's unbelievably complex and when you laugh all of that goes away and you just take a big breath in and then you go ha ha ha ha out on an exhalation and each of those exhalations is just air being squeezed out of you and really big sort of pushes by the rib cage much bigger deflections than you get for speaking much more rapid the tongue doesn't move at all the mouth just opens.

7:28What's happening with that will vary from person to person to some degree, but it remains a very primitive way of making a sound. And of course, that's consistent with the fact that it's a sound we're able to make from very early in life.

7:37Caroline Steel:Okay, so is there anything you can kind of put your finger on in terms of this makes a laugh more like this? So for example, if you have a larger rib cage or something like that, is that going to make your laugh deeper? Yes, if you're bigger, just physically bigger, you'll have a physically bigger vocal tract and you will produce sounds that have an overall lower pitch and the length of your vocal tract will also reflect almost like the timbre of your voice. So that definitely has an influence. Do our hormones play a role in how our laughter sounds as well? Well, in terms of the really big effects that testosterone has on the male voice, teenage males go through this period where their voice breaks and you get this secondary descent of the larynx.

8:18So you've got effectively a much larger vocal tract in adult males and it gives you a very distinctly different voice and much larger pitch variation between males and females than there is in height. Wow, OK, I didn't realise it was that much of a difference. I mean, I have a recording of my son laughing before he'd gone into puberty, so his voice hadn't broken, and he's trying to do a funny voice and his voice breaks because he burps and he starts laughing. But his laughter sounds exactly like mine. Oh, really? And it doesn't sound at all like mine now because he's an adult male and his voice is broken, but actually I suspect there's probably still patterns that are similar that were driving why he was sounding like that when he was laughing as a child.

8:55Caroline Steel:I imagine that like me, you're dying to hear that recording of Sophie's son burping and then laughing. So first, here's a reminder of Sophie's laugh. And now here's her son, starting with a silly voice. By most places, it is close to some things.

9:19Caroline Steel:And here's Sophie's laugh one more time.

9:25Caroline Steel:Unbelievable. Sophie and her son sound identical, just like listener Limba Kani and his dad. And perhaps that's because our laugh is affected by physical things like our height, which is partially determined by the height of our biological parents. But where did our parents get their laugh from? And how about our parents' parents? Gil Greengross is an evolutionary psychologist from the University of Aberystwyth in Wales in the UK. He's an expert in laughter. So like Sophie Scott, he has one of the best jobs going. Well, I always loved to laugh and I thought, why not study humour? Because it's one of these behaviours that everyone is experiencing it every day.

10:12And we don't usually even acknowledge or notice how much we laugh during the day. And for such an important phenomenon that actually it's one of the things that maybe define us as human, there was very little research on the topic.

10:29Caroline Steel:Am I right in thinking that Darwin wrote about laughter? No, you're not wrong about that. So he wrote the book, The Expression of the Emotion in Men and Animals in 1872. and he noticed that when you tickle different animals, his favourite was chimpanzees, they tend to laugh. So he came up with the idea that maybe humour in humans is like tickling of the mind. So that's where that's actually the first evolutionary theory of humour was invented by Darwin. So Darwin tickled chimpanzees, which means primates must laugh too. Yes, and this is something that a lot of people find surprising. So there's quite a lot of research on other primates like chimpanzees, bonobos, orangutans, and they have two distinct facial expressions.

11:26One is a smile, that when they smile with the teeth touching each other, and this happens usually when two individuals are in conflict with each other. And then one of them loses the fight and they do this kind of display to show submission. And it's probably to signal the other individual that it's OK, we are good friends, I'm not an enemy, I'm laughing at your jokes, I'm fine. So that can save a lot of injuries and prevent the situation escalating any further.

12:03Caroline Steel:So primates smile to concede a fight and clear the air. and they have another facial expression linked to laughter. The other display is kind of a play face, laughing with open mouths and that usually arises in a playful situation when children play with each other, rough and tumble and this is a sign of enjoyment. OK, do other animals laugh? So there is quite a lot of research on rats that show that they can laugh too. They make sound that we cannot hear it in human ear, but we can amplify it as they make kind of a chirping sound. And when people tickle the belly of a rat, they tend to make this sound.

12:52And we know that it's enjoyable because they're looking at the finger that tickles them to get more and more that they never get satisfied. It's kind of funny. And they're not the only one. And penguins also laugh. Even dolphins might smile. So it's clear that laughter and smile have a very long evolutionary history. So it didn't start with us.

13:16Caroline Steel:Do we know when humans first started laughing? The last common ancestor from humans and chimps, for example, was about six million years ago. So somewhere between six million years and today, laughter and smile evolve into actual humour. And so with the evolution of language, we were able to laugh at not just nonverbal cues, we were able to actually purposely make each other laugh. I find it mind-blowing that our ancestors, the ancestors of humans, were laughing for potentially millions of years before we started speaking. Right, that's correct. So as we saw, there is a long evolutionary history for smiling and laughing.

14:02Caroline Steel:You've looked at specifically whether our sense of humour, not specifically our laughter, but our sort of general sense of humour can be inherited. What did you find? So in a recent study, me and my co-authors look at whether the ability to be funny is inherited. And to our surprise, we found inconclusive results in related to actual humor or objective humorability. So we didn't find a strong genetic factor for that. So all humor production was attributed to environmental factors. So the way you grow up, for example, hanging out with friends, with peers. But what did surprise us was the subjective humorability.

14:50what people say about themselves, about their sense of humour, that was actually highly heritable. So identical twins were much more correlated with each other in the responses of humourability, while non-identical twins were quite diverging their views. OK, so far you've basically found that identical twins are more likely to sort of rank their sense of humour, have confidence in their sense of humour in a similar way,

15:17Caroline Steel:but they're not actually more likely to have a similar sense of humour to each other. Right, exactly. So our listener Limbikani wants to know if he's inherited his laugh from his dad. They sound very similar. And based on all your research and knowledge in this area, what do you think? Do you think we could inherit our laughs from our parents? So although there is no specific studies that tested this hypothesis specifically, my feeling is that it is an inherited trait. And I say that because not just most psychological traits and physiological traits are at least partially inherited, but other humor attributes are also inherited.

16:01So they've been studied about humor style. So if you use an aggressive humor style, then this is something that is inherited. Also, if you use more benign humor, that's also a trait that is inherited. We don't have a study specifically looking at laughter, but my gut feeling is that if we run a study like that, we'll find quite a substantial genetic factor for that.

16:28Caroline Steel:The way to do that study would be to compare laughter in identical twins to laughter in non-identical or fraternal twins. That's what we're exploring next. This is summer at its peak. Whole Foods Market Summer Fruit Fest is your invitation to eat the season. Fresh, organic, and bursting with flavor. Start your day with peaches and organic blueberries and yogurt. Build a grazing board with fresh fruit, prosciutto, and artisanal cheese. Then fire up the grill with no antibiotics ever, proteins, and fresh produce. Savor the season. Shop Summer Fruit Fest at Whole Foods Market. Apple Vacations, where your story starts.

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17:40Caroline Steel:You're listening to CrowdScience from the BBC World Service, the show that answers your science questions. In this episode, we're answering a question from listener Limba Kani in Zambia. He wants to know if he gets his laugh from his dad. So, is laughter nature or nurture? At the start of the show, we heard about twins who were separated at birth and then reunited three decades later. They became known as the Giggle Twins because when they were together, they couldn't stop laughing. The Giggle Twins grew up in England and they met probably in their early 30s. And they had similarities such as the same crooked pinky finger and they both had met their husbands at dances.

18:32Caroline Steel:This is Dr Nancy Siegel. She's an evolutionary psychologist at the University of California, Fullerton in the USA and she's CrowdScience's resident twin expert. I'm a fraternal twin and I can tell you that my sister and I have very different laughs. Oh really? Yeah, we laugh at very different things and the sound is quite different and we were raised together. Nancy met the Giggle Twins shortly after they were reunited. They both were extremely unpolitical and the two of them also had miscarriages and then went on to have two girls and a boy. As you can probably imagine, at the time, many people were fascinated by their story.

19:12Caroline Steel:Here they are on the BBC TV show Getting to Know You Again in 1997. You didn't discuss what you were going to wear today, but you have come. The shoes. The same shoes, the same stockings, similar skirts, similar jackets, just slightly different shirts. It happens all the time. Right, all those years, all those years you spent apart, were you doing similar sorts of things? Oh, yes, yeah. We fell downstairs when we were about 15, which left us with weak ankles. Both of you? Yes. We had two boys and a girl in that order, and our second sons are born within three weeks of one another. and the miscarriage was possibly the same time the same year.

19:55Caroline Steel:Were you the same sorts of school children? Were you good at the same...? Yes, at art. Yes. Hated maths. Hated sport. Hated sports. Clearly the same things make you laugh. Yes. We're our own best audience. Nancy fondly remembers their uncontrollable laughter. It was just a constant stream of giggles. I wouldn't say it was high pitched or low pitched, but they would look at one another and they would just laugh like crazy. And it was their sound was completely similar. I mean, if I had my head turned, I could never tell you which one Barbara or Daphne was the laugher. so how do you think that's possible how do you think their laughs came to sound so similar when they've lived apart for you know at least 30 years well Caroline that's probably an easy question to answer because the twins were genetically identical and so what that means that the vast majority of their traits are going to be expressed in similar ways and so voice quality laughter that's all going to be pretty much the same it's a it's not something we've systematically studied across twin pairs.

21:07I think that's unfortunate.

21:08Caroline Steel:So there's not been a sort of systematic study where you've looked at the laugh of separated twins to find out whether or not laughter is genetic or socially influenced? No, we haven't. And that's really surprised me because sometimes we think we've studied everything we could. And then something else always comes up, such as shoe size. We never studied shoe size. And the quality of the laughter would be fascinating. Now, there have been a number of different studies by different investigators of different countries that look at things like humor production, or whether you find a certain cartoon funny, or can you produce a funny line to this cartoon without a caption?

21:46So there have been studies along those lines, but never one on the quality of laughter, which really surprises me. And I think that there's plenty of people who'd be interested in doing such a study.

21:55Caroline Steel:Yeah, because I think it's really interesting to what extent our laugh is given to us at birth, or whether it's something that we sort of learn based on what we hear in our environment. Well, but the thing is that we're all in similar kinds of environments, let's say children in a school classroom or recess, and children's laughter is very individual. And I remember in college, there was a guy who just laughed in these big, deep guffs. I don't know how else to describe it, but it was very, very strange. And then there were some people who just kind of fake a laugh. I mean, there's all kinds of laughters.

22:27And yet, we all just do it in our own individualistic way but because identical twins whether raised apart or together have the same genes they're more likely to do it in similar ways.