This One's a Tear Jerker

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1:25Welcome to the Rest of Science with me, Hannah Fry. And me, Michael Stevens. And we thought we were talking about crying today. Specifically, why do humans cry? Why do you cry, Michael? I don't want to get into it right now. But I want to know why. Because there's only one animal on this planet that cries emotional tears. Are you sure? I know that there's some debate. There's some stories that camels have cried in emotional moments, like when they're reunited with their babies. One camel, by the way, not camels. A single camel. But what is your feeling here? Do you think it's uniquely human to cry emotional tears?

2:06Because as we all know, anything with wet eyeballs is going to have tears. Yeah, of course. But we produce a bunch when we're emotional. And we have not seen that in other mammals or birds. Because I mean, wet eyes, there's three reasons why you have wet eyes. There's like the sort of lubricating tears that just stop your eyeballs from... Drying out. turning into, you know, raisins. There's the reflex. If you get something in your eye, it needs to sort of water and flush it out. And then the third one is the emotional tears, which supposedly has all kinds of hormones inside of it, which make it chemically distinct from the previous two.

2:44And that's the one that we're saying is that, yeah, we just don't see it in other animals. And maybe we haven't looked closely enough, but you don't have to look very close at humans to see emotional tears. Yeah. Weeping and sobbing. So why? Who was the first person to weep? At some point in evolution, we went from being hominids that didn't cry tears to suddenly there was a first person who was like overwhelmed. Maybe it was a baby and tears came out and they were like probably freaking out. Their parents were like the baby's leaking. What is this? And now the tears are just a thing. Maybe actually the distinction between not crying and crying is slightly fuzzier than you're describing because you could still have tears running down your cheek, but it's like the cause of it, the kind of the thing that caused you to cry or caused the tears to leak from your face.

3:41That's the thing that slowly changed over time. Yeah. Okay. So let's start there. What was the last thing that caused you to cry? So my, well, mine's going to be a bit of a downer, but my dad died this year. So I cried very much at his funeral. I was really good at the morning. Yeah. There's a lot you just said there. You were really good at the morning. What do you mean by good? Like a sight to behold? I was the picture of morning. Of morning. And that's just it. I think, and I think we'll get here through the talk, that I think it's about the picture. It's about signaling something. Okay, that's so interesting.

4:17Not by choice, though. Well, that's one thing that I think is interesting, because I was giving the eulogy, and there was a moment in the eulogy where I caught myself, and I knew that I had the instinct to cry and was desperately trying to repress it. My voice went high, I had the lump in my throat, like all of the kind of physiological responses that you have to trying to suppress this cry. And that, I think, does tell you that these things aren't necessarily, you don't necessarily have agency when it comes to crying. That's right. This matters to me because I'm, I think probably shouldn't be, but I'm obsessed with figuring out what it is that describes humanity as simply as possible.

4:58And so looking at the things that differentiate us from other animals on this planet is a place to begin. And emotional crying is one of them. Oh, Michael, when did you last cry? Hannah, I'm glad you asked because did you like my Hannah impression? That was really good. It was good. I think I'm a bit more cockney than that but sure i govna wouldn't you i don't really know english accents when did you last cry the last time i cried was very different than yours because i was completely alone uh i was watching about schmidt right and i guess this is a spoiler but i'm going to say it anyway because you can go and find your own sad movie but at the end this child that he has been that he adopted, the main character, Schmidt, he gets a drawing from the child and it's a drawing of him and the child holding hands.

5:48And I just got so wet in my eyes. I didn't like sob. It was a quiet cry, but I was just so overwhelmed at the sort of patheticness of how small this event was and yet how powerful and how much meaning it had. Was it that you were overwhelmed by the emotion of the scene in the film? Or was it that it was tapping into something that you felt about your own family, your own, you know, your own child, your own experience? I don't know. I didn't even have a child at this point. Oh, wait, hang on. Your child's like many years old. Look. Have you cried this decade? All right, you got me. I cried more recently.

6:33I'll just I don't I don't want this to become a political discussion, but I cried after watching a politician speak and the politician said something that was just so humble. Yeah. I also when I need a good cry, I do late at night turn on military funerals. Yeah. The circumstance and pomp of these ceremonies with the other soldiers there doing the 21 gun salute who may have not even known the deceased. the flyover in with the empty man formation. It's just so big. The funeral procession going down the freeway and just people have come out onto the street just so their kids can see. To see what?

7:17It's so human. It's so weak and humble, but yet so significant at the same time. It's like the bigness and the smallness of the entire world. the specific moment that triggered me when I was speaking my dad's eulogy I'd written this eulogy and I'd talked about the funny things that we'd done together these amazing things and I'd written that I remembered the feeling of holding his hand when I was a young girl and that was the thing that got me it was that connection of knowing that I'd held his hand that morning when he was in the casket and then that that very visceral sensation of being a child and looking down at your dad's hands when they're covered in dirt from work.

7:58And I think that's it. It's like, it's the bigness and smallness simultaneously of those moments that can be overwhelming. Isn't it? Yeah. I saw my father's body as well. They had a room that his body was in and they said, yeah, well, you guys can go and, you know, say last things to him. And it didn't really hit me until that moment when they asked me to go first that I was like his son. It was like really, Yeah. See, and this is starting to make me feel like my eyes have a little bit more fluid in them. Yeah. But it's not because you're here or these people are here because I've cried mainly alone.

8:36I'm always alone and I've been alone in those circumstances. And yet I still did this. Still got watery eyed. It is strange, isn't it? It is strange, the things that trigger you. But it's also not strange. Like these stories all make complete sense, right? No one's going to go, you cried when you watched a funeral. But to put it in the context of no other animal has been definitively observed crying emotional tears. That's when I think we need to say, what are humans up to? I'm still feeling very emotional. I want to now just shift to something that I think will make you cry for a very different reason.

9:16Go on. As I was looking into theories of emotional tears, I found a equation out of some research from Alabama. And I think, oh, you're going to love this. All right. You ready? Here's the equation. Crying equals meaning plus vulnerability divided by sensory threshold. Okay. This is one of the fake equations that exist in the world. I knew you'd call it. And I've got to be honest with you, I have a severe allergic reaction to them. Tell me why. They make me actively angry. There's a multitude of reasons. For one thing, how are you measuring vulnerability? What's the unit of vulnerability that we're doing?

9:58It's the metric unit. One pathetic. Well, I don't know. But I see, yeah, I see what I agree with you. Okay. Also, what was it? Sensory threshold, did you say? Okay. So what happens when your sensory threshold is zero? That means you're infinitely crying? Ooh, yeah. Yeah, the space-time continuum is destroyed by your crying. Or what about if you've got a very high threshold crying? I mean, what about if you've got a negative sensory threshold? Do you go to negative crying? Negative crying. You suck moisture into your eyeballs. Absorbing water from your eyes. You need to stop negatively crying. I'm drying up over here.

10:30Also, meaning. Sorry, what is the meaning of meaning? I think I'm not saying that there's, you know, there's some ideas behind that, right? It's like the value of an idea to you, how vulnerable you're feeling, you know your own personal threshold but this is like i mean putting it into an equation gives it this right false sense of precision a false sense of precision and correctness yes i think what's being said here is that there's something called meaning and there's something called our vulnerability to it but then it's all mediated by just how where our threshold is for crime the lower it is the bigger that ratio gets and the more crime there is but yeah you're right these are such soft terms.

11:12I'm okay with that idea. What you've just described is, I think that's, I think that's good. I mean, every, the two situations that we've described about us crying definitely fit into that category, right? But also there's this idea of the threshold that you as an individual have, that some people are more sensitive to crying than others. I think I'm okay with that broadly as a rough idea. I think that's, that's, that's good. It's just don't make up equations. Yeah, fair enough. Not in my presence. So then let's, let's look at the data. Let's look at how crying begins in the life stages of a human.

11:41In a baby. In a baby. Yeah. Okay. They're famous criers. Yes, they are mega criers. I mean, the thing is, is that crying in babies, there's different versions of this, right? Because there's the crying as a sound for different reasons. So whether they're hungry, whether they're uncomfortable, whether they've got gas, whatever it might be. But that there's a really clear evolutionary purpose for that, which is in order to signal for attention to the carer to sort of fix the situation. Right. To get nurturing, to get attention. It's a distress call. And you're right. We see this in all kinds of animals.

12:18Absolutely. There is some work, I don't know whether you've come across this, this is by a nurse called Priscilla Dunstan. And she has a theory, right, that there's actually the different reasons why babies cry changes the sound that they make purely because there is some reflex that starts the sound. So for instance, when a baby is hungry, like, and we're talking really, really young here, right? Like first, first three months of life, uh, when they would be suckling, they, uh, the tongue in the mouth goes into a certain position that makes a like sound. Or there's a few others. There's like a, if they're really uncomfortable from trapped wind, it makes more of a like eh, eh sound.

13:00Or there's like a, you know, one beginning with more of a huh sound, that kind of thing. Now I should tell you that there have been like some small scale studies on this and it's really difficult to definitively pin down that this is what babies are doing. But there are lots of parents who say that this is actually a really useful rule of thumb rather than a hard and fast scientific rule. You can kind of figure out what the baby is trying to say more specifically than just look at me, give me attention. Exactly, exactly right. Okay, that's making me think, I don't know if you know the answer to this, but when a child is extremely young, it's still breastfeeding, the sound of its tears can cause the milk to, does that depend on how the cry sounds is what I'm asking.

13:42It actually makes your boobs hurt. Yeah. Like it's unbelievable. Any cry or does the hunger cry cause it more? Well, it's specifically your baby as well. Only your baby. So the thing is that the hormone that creates letdown, that essentially allows the milk to run, there are a few different ways that it can be signaled. And one of them is an auditory cue. And within 48 hours of your baby being born, your body essentially learns your baby's cry and it triggers the production and letdown of milk when it hears that signal. And I think it is, I'm talking personal experience now, rather than scientific stuff.

14:25But I think it is specifically cry because there's a different cry when your baby is hurt. Right. And that doesn't signal the milk. And these all sound like really deep evolutionary mechanisms. But what these two-day-old babies don't do is cry with emotional tears. They're not watching military funerals. They aren't. They're crying by creating a vocalization, but they're dry on the face. They are. Now I've read that it's around four to eight weeks of age that you might start to see tears. Physical tears. But are they emotional tears at that stage? You know, Darwin. Yeah. I don't know if you've heard him.

15:05I've met him a few times. He's kind of a big deal. Yeah. He wrote this book. As well as The Origin of the Species and Descent of Man and Harry Potter and the Chamber of Secrets, all of his important books, He also wrote this book, which is called The Expression of Emotions in Man and Animals. And this is, it's a stonking read, Michael. I would thoroughly recommend it to anyone. He's got an entire chapter on blushing. He's got an entire chapter on weeping. He goes around just observing all kinds of animals and all kinds of humans in all kinds of situations. He's got a sweaty hippo who's very cross in labour, been there.

15:41He's got an impatient horse. He's got an orangutan who desperately wants some apple. It's like, there's, it's honestly, it's absolutely delightful. But he also, this is, I think the first book to have ever included printed photographs inside of it. And he has within it a study of upset babies. Oh my goodness. Isn't that amazing? So what you have here is a page of six images of very upset children. Yes. And they look like they're Victorian age children with their black and white photos. The kids look like they're in distress. Yeah. I mean, I think that they're ones in a sort of high chair. They're all wearing like really cute Victorian clothes.

16:26They're all very chubby. They're all just absolutely gorgeous little kids, but they're all crying. And they've got faces that are immediately recognizable as crying. The eyes are closed quite shut and the grimaces on the face. They're very sad. They're very cute and as normal children are when they're upset. But Darwin made a study, I mean, both of which muscles were being contracted in their faces as they were crying. But he also made a study of his own infants. And he noted that one of his children, one of his babies, at 77 days old, he accidentally brushed the cuff of his coat across their open eye.

17:05Accidentally, he says. and that caused tears to stream down their face. Okay, at 77 days. 77 days, but he was pretty sure that they weren't crying emotional tears, it was reflex. It wasn't until 139 days that he felt that they were weeping emotional tears. Okay, so it took 139 days for Darwin's child to finally start shedding emotional tears. What is that? 4.56986 months. Yeah. Wow. Yeah, I mean, 200 ,160 minutes if you like. If you're rounding, yeah. if you want that. Now, a theory I've heard about that transition, which to me feels like a kind of metamorphosis. From not crying to crying. Yeah, is that at first this distress call, just like you'll find in birds and other mammals, gets the attention that you need for all kinds of reasons, just to get it to stop because it's annoying, to get it to stop because it could alert predators of your position, but also maybe just a reflex, like the milk let down going, oh, my body, my DNA tells me what to do here.

18:11But also that danger, the danger of alerting predators to where you are and aggravating the parents eventually needs to disappear. But the helplessness and the need for care never does in our species because we have such extended adolescence, pretty much our whole lives. I think we're always childlike in ways that no other animal is. In the sense that we play, for example. In the sense that we play, in the sense that we're always like learning new things and always can learn new things. So instead of making a racket, a vocal racket, when we want to signal this, we can do it with the way our face looks and with tears coming out of our eyes.

18:52A physical signal rather than an auditory one. That's right. So, okay, interesting idea. But then I don't know if you've ever met a two-year-old. They are very noisy. Yeah. And they cry very loudly. Yeah. So what's that about? Well, okay. Yeah, right. I guess they're not done with the metamorphosis yet. They're still in their cocoon gelling into a tear crier and not so much of a loud, sober waler. Sure. But then also, I mean, there's sort of like loud sobbing wailing that you get from a young child, which is genuinely I'm hurt, I'm in pain, or I'm hungry, I'm tired, I need something, and I can't quite articulate what it might be.

19:39That is different from watching military funerals. Yeah, it is. It's certainly different that a child will cry when they physically hurt themselves, when they fall over. But I don't. I will cry when I hear a speech. But if I broke my arm, I probably wouldn't cry. Oh, I would not feel good. Oh, I would. My lip would be so stiff. You guys would be like, excuse me, I'm the British one here. Thank you very much. I know, but I'm just saying you've got competition. No, but you see where I'm getting with this. Like as we age, the things that make us cry are very different than the things that made us cry when we were even more helpless and helpless in a different way.

20:20When you're hungry, you don't always cry the way you did when you were two or one or less. Agree, agree. And yeah, I don't think anyone's saying that babies are gonna watch a funeral and be able to understand and feel overwhelmed. They might be overwhelmed just because the sensations. I mean, about Schmidt is 12 plus. They're not even allowed. They're not even allowed. They should not be watching it. Okay, so there's definitely lots of evidence of other animals crying for pain or crying for hunger, all of that kind of thing. I think that there is evidence of other animals and making auditory and like behavioral cues in an emotional way.

20:56So elephants is the classic example here. Lots of people have reported that they've seen elephants engaging in mourning behavior. There's one particular incredible story about an experiment that went wrong. So I don't know if you know this, but elephants have names that they give each other. How do they communicate? They rumble. They like, it's an auditory thing. They use their trunks to kind of call out names. It looks like elephants actually have a vocabulary of lots of different words. They have a word for bees. They have a word for human. They have a word for bad human. It's like actually quite a lot of complexity to animal language.

21:33Anyway, what you can do is you can turn up with a truck and a loudspeaker and play out a recording of an elephant calling another elephant's name. And if that elephant is within that herd, just that one elephant will turn around. You'd be like, Billy! And the elephant would be like, yes? Wow. Which is amazing. That is really amazing. You have to be really, really careful when you do this experiment. It's called a playback experiment. And the reason why is that a group of researchers went out into the savannah, played a sound of an elephant shouting another elephant's name. But what they hadn't realized was that the elephant they'd recorded had since died.

22:10Oh no. And so the herd, who she used to belong to, suddenly got extremely distressed at hearing this voice effectively from the past. From a ghost. From a ghost. And her daughter, the deceased elephant's daughter in particular, was going through the bush for days and days and days looking for her lost mother. Oh my gosh. So this kind of idea of mourning behavior that you see in animals, we know that it exists, not just in an observational way, but in those kind of slightly unfortunate situations where it's actually been an outside intervention, a human intervention that has created this mourning behavior.

22:49You get this with whales too, right? Like whales will carry the carcass of their dead children, often for days. They'll form a hub around a whale that's dying. You know, there's lots of like extremely complex mourning behavior that you see in animals. And over the years, we've had lots and lots of reports of people who work closely with elephants, people, fishermen who've worked closely alongside whales, who claim that they have seen emotional tears in these situations. Really? But it's just really difficult to prove, right? It's really difficult to prove. How do you know that it's not dust that's got in the eye?

23:29How do you know? I mean, it's a whale, for goodness sake. It's in the water. But also, if you decided to do an observational study of a human, right, you could follow you around since 2020 and have very little evidence of you crying at all. Yeah, that's true. It's a really rare event. That's true. So I'm willing to admit that we don't know conclusively that only humans cry emotional tears. But we don't have any hard evidence that any other animals do. We don't have hard evidence. And like personally, I think that these other animals, who knows what they're feeling, but I'd like to believe, and I think we almost have an obligation to believe that they're feeling things quite deeply.

24:08They're expressing it differently though. they're not contorting up their facial muscles in a way that creates this redness this puffiness this wetness that is almost hard to hide maybe they're doing something that we can't quite pick up on but their other conspecifics immediately go they're crying and that i think gets us to what a crying person causes us to think about them which maybe we should do after a break

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26:03All right, welcome back. We are talking about crying. And I want to move on to whether or not crying is a choice. How much voluntary control do we have over our emotional tears? I mean, sometimes none at all, right? I mean, I don't know. Have you given that you've only cried once a century? No, come on. I cry. I cry just the right amount. That's the right amount. But definitely I've had this experience numerous times where you get that feeling in your throat, the lump in your throat. And what that is, is there's a competition in your throat, right, for what the muscle should be doing. Part of you, your reflex is to help you breathe.

26:45And the other part of you is your reflex is to try and suppress the cry. And so what you end up with is this tension in your muscle that feels like a lump in your throat. But also what happens is when you've got this tension, you lose the fine motor control that your throat normally has, which is why your voice starts to get really squeaky. Wow. Yeah. That's fascinating. Isn't it? The fact that we even are concerned about, should I allow this to happen or try to resist it, says so much about the cultural and psychological importance of crying and what it means to us. The thing is, we suppress a lot of emotions.