It’s something so natural that we take it for granted — but when you think about it, it’s a little strange. Why does water come out of our eyes? And why does it happen when we’re happy? Or sad? Or scared? Or exhausted?
In this episode we dive into our mysterious emotional tears, find out why onions make us cry (and how to stop it), and hear about the eye-protecting trio of tears that makes Eyetropolis a safer place. Plus: Our Moment of Um explores why we sweat when we’re nervous.
This episode was originally published on Sept. 26, 2017. You can listen to that version here:
For crying out loud: All about tears
by MPRAudio Transcript
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MOLLY: You're listening to Brains On, where we're serious about being curious.
SPEAKER: Brains On is supported in part by a grant from the National Science Foundation.
MOLLY: Molly, I'm here and ready to tape this episode.
MOLLY BLOOM: Oh hey, hang on a sec. I'm just putting the finishing touches on our studio setup. You can have a seat right there.
MOLLY: On this pile of tissue boxes?
MOLLY BLOOM: Yeah.
MOLLY: Where are my headphones?
MOLLY BLOOM: Oh sorry, under the pile of hankies right here. I was going to stuff these all up my sleeves. Do you want some?
MOLLY: Sure. So you're sitting on a pile of tissue boxes too.
MOLLY BLOOM: Mm-hmm.
MOLLY: Oh, and there's more under the table. And are those--
MOLLY BLOOM: More tissues inside the light fixture? Yep. I just wanted to make sure we were prepared for this episode. Questions about tears and crying have been pouring in from our listeners.
LIBBY WANG: Hi, my name is Libby Wang from Moraga, California. I'm here with my brother Elliot.
ELLIOT: Hi.
LIBBY WANG: And my question is, why do tears come out of your eyes when you cry when you are sad?
DYLAN: Hello, my name is Dylan. And I live in Tallahassee, Florida. Why do you cry when you're sometimes very happy, or you're laughing very hard?
DELANEY: My name is Delaney, and I'm from Toronto, Canada. Why does pain make people cry instead of some other physical reaction?
CALEB: Hi, my name is Caleb. I'm from Mountain View, California. And I'm 9 years old. My question is, why do we cry when we're sad?
ELISABETH: My name is Elisabeth from Cincinnati, Ohio. My question is, why do noses get drippy and start getting runny when eyes get wet when I cry?
MOLLY BLOOM: Hang on to your hankies, we're going to answer all those questions right now.
MOLLY: Keep listening. But we're just talking about crying, right? Not actually crying ourselves. Why do you have so many tissues?
MOLLY BLOOM: Uh, they were on sale?
[THEME MUSIC]
You're listening to Brains On from American Public Media. I'm Molly Bloom, and my co-host today is another Molly. Hi, Molly.
MOLLY: Hi, Molly.
MOLLY BLOOM: Hi, Molly.
MOLLY: Hi, Molly.
MOLLY BLOOM: Hi, Molly.
MOLLY: Hi, Molly.
MOLLY BLOOM: Hi, Molly.
[ECHOING]
Molly is 11 years old from Los Angeles. Now Molly, what made you curious about crying in the first place?
MOLLY: So my mom was telling me about this science fiction book, where there was a lot about specifically crying and body moisture. And it just got me thinking about all of that in general.
MOLLY BLOOM: Do you remember the name of the book?
MOLLY: Dune.
MOLLY BLOOM: Oh Dune. So do you feel better after you cry?
MOLLY: Yes, I often do. Sometimes I just feel worse, but usually, I feel much better.
MOLLY BLOOM: And have you also cried when you're happy?
MOLLY: I don't really cry, but tears can definitely come out of my eyes when I'm laughing really hard.
MOLLY BLOOM: Oh yes, I have cried many times from laughing so hard. So why do you think that we cry?
MOLLY: Originally, I thought that we might cry as a way to communicate how we're feeling with people that we know. So like, if we're hurt, and we were having trouble making words, they can tell that we're feeling something because we're crying.
MOLLY BLOOM: That's a really good idea. And what are some times that you have teared up besides when you're sad or hurt?
MOLLY: When I'm really, really tired. I can start sobbing. And it's really annoying because I also like to sleep. And it's kind of hard to cry when you're sleeping.
[LAUGHS]
MOLLY BLOOM: When we cry, we produce tears. And tears are really interesting and also really important.
MOLLY: When you've cried, you've probably asked yourself the same question that was sent to us by Sam in Cheverly, Maryland.
SAM: Why are tears salty?
MOLLY BLOOM: Well, you may have noticed that mucus that comes out of your nose is salty. Blood tastes salty. And sweat is salty.
MOLLY: And that's just because our bodies are pretty salty.
MOLLY BLOOM: Maybe you've heard the word "electrolytes." That's another word for the salt ions that are in our bodies.
MOLLY: Tears come out of your body, so they're salty like us.
MOLLY BLOOM: All tears contain some combination of water, salts, proteins, oil, and mucus. They come from your lachrymal gland.
MOLLY: The lachrymal gland is at the top of your eye. From there, tears move across the cornea or the surface of the eyeball. Then they usually drain at the lachrymal ducts.
MOLLY BLOOM: Those are located in the corner of the eye closest to the nose. In fact, the lachrymal ducts drain into your nose, which explains why your nose runs when you cry. Of course, sometimes you have too many tears to drain, and they spill down your cheeks.
MOLLY: Now you might be thinking, all tears are pretty much the same, right?
MOLLY BLOOM: Not so. There are three distinct types of tears-- basal tears, reflex tears, and emotional tears. They all help with different things.
MOLLY: Like, keeping your eyes moist, and your vision clear.
MOLLY BLOOM: Or defending your peepers from invaders. So how did this trio of terrific tear teammates first team up?
MOLLY: Well, maybe it was something like this.
BASAL TEARS: Hey fellow tears, thanks for meeting me here. As you know, I'm basal tears. You can call me Basal Tears.
REFLEX TEARS: Sure thing. I'm Reflex Tears. Nice to meet you.
EMOTIONAL TEARS: Yeah, I'm Emotional Tears. We saw the ad you posted online, tears needed for a super secret project. Sounds mysterious. I like being mysterious.
TODD: Hey guys, I brought coffee. It's cilantro spiced iced lattes. Yum.
REFLEX TEARS: Cilantro spiced? Is that even a thing?
EMOTIONAL TEARS: Yeah. Sorry Todd, I'm going to have to pass.
BASAL TEARS: Say kid, are you a tear? This is a gathering of tears.
TODD: Well, I'm not a tear yet, but I want to be. Hi, I'm Todd.
BASAL TEARS: Sure. Nice to meet you, [CLEARS THROAT] Todd. Well, let's get started. I'm looking to form a super team of super tears. As you may know, our fair home Eyetropolis is under constant attack.
REFLEX TEARS: Yeah, dust, pollen, that drying heat.
EMOTIONAL TEARS: Not to mention other cities picking on it, making it feel bad-- not cool.
TODD: And fingers. People are always sticking their fingers in Eyetropolis. Right, guys?
BASAL TEARS: Fingers? I guess they could be a problem. Anyway, I want tears with different powers to help protect our precious eyeball home. Now I, Basal Tears, bring a lot to the table. I'm ever-present across the eye. Released in every blink, I keep things moist. I have three layers-- a mucus layer to help my wetness hold on to the eyeball, an aqueous or watery layer that actually moisturizes the eye and protects against invasive bacteria, and a lipid or oily layer.
TODD: I like oil, so slick.
BASAL TEARS: That last layer helps keep the others from evaporating and keeps the surface of the eye smooth so its vision is clear. Obviously, I am most excellent and fantastic at protecting Eyetropolis. But occasionally, I could use some help.
REFLEX TEARS: Oh wow, I've been waiting for this kind of gig. I think I'm your tear. Whenever Eyetropolis is attacked by major irritants like dust clouds or harsh cold winds or Dr. Onion's evil vapors, I flood the place with my reflex tears-- whoosh! They're full of antibodies that fend off evil bacteria. Plus there's usually a lot of them. They flesh things out right away and rehydrate the city-- bada bing, bada boom, reflex tears saves the day.
TODD: Impressive.
EMOTIONAL TEARS: My powers are a little more mysterious. But I think I can really help. My tears come out when the city is feeling upset, harmed, wronged, or even sometimes happy. Whatever the trigger, the city is usually all wound up in some way. It seems I help calm things down. How? My powers are mysterious. Scientists and researchers, even I don't fully understand them.
Also, when I fled the city with my tears it signals to others that we could use some help. Other cities often rally around to comfort us. It helps build bond so we're stronger in the future. It's a mystical ancient power that I think could help your team.
BASAL TEARS: Most intriguing. Yes, I think you'll fit right in, Emotional Tears.
TODD: Well guys, I'm not a tear, but maybe I could be. Like, what if I squirted out of the eye like a water pistol? [LAUGHS] You know, shooting a stream of tears at our enemies like a salty fire hose, that'll teach them.
REFLEX TEARS: Huh?
EMOTIONAL TEARS: Huh? That's weird, Todd.
BASAL TEARS: Yeah, that's not really what I'm looking for.
TODD: OK, how about I'm like a hard tear. Like, I come out all rough like a diamond. What's up, enemies? You can't hurt me.
REFLEX TEARS: Are you crazy? That would scratch that metropolis cornea. No way.
BASAL TEARS: You know, maybe we're best as a trio-- basil tears, reflex tears, and emotional tears. Protecting Eyetropolis together!
ALL: Yeah!
BASAL TEARS: Flushing out evil in the blink of an eye, the three muske-tears!
EMOTIONAL TEARS: Sounds good.
REFLEX TEARS: Right on!
TODD: And their sidekick Todd, the neon yellow tear.
BASAL TEARS: Uh, no.
TODD: Todd, the burning tear made of peppers.
EMOTIONAL TEARS: Why would you even?
TODD: The stinky tear-- you can smell me coming from a mile away.
REFLEX TEARS: Just stop.
TODD: The cheer tear-- I come out with pom-poms, and I do the splits.
BASAL TEARS: You know Todd, maybe you should try a different city, perhaps Noseville could use someone with your creativity.
TODD: Noseville? Yeah. I could be a booger. Todd, the school bus booger. I'm there when you're riding the bus, and you need to flick something at that person.
BASAL TEARS: Sure, sure. We've got some planning to do. So why don't you run off to Noseville now and offer your services? In the meantime, tears--
ALL: Let's protect Eyetropolis!
[TRIUMPHANT MUSIC]
MOLLY BLOOM: So there are three types of tears-- basal, reflex, and emotional.
MOLLY: Basal tears are in your eyes all the time.
MOLLY BLOOM: But reflex tears need to be triggered by something. And there's one trigger in particular that our listeners are really, really curious about.
HENRY: My name is Henry from Maple Grove, Minnesota. And my question is, why do onions make you cry?
JOSEPH: Hello, my name is Joseph. I am from Ireland. And my question is, why do onions make you cry?
MOLLY: Brains On producer Marc Sanchez is here with an answer.
MARC SANCHEZ: Ever wonder how the produce section of the grocery store can have a mound of onions but nobody in the store is crying?
RABI MUSAH: If you just hold an onion, you don't cry you don't produce tears. But when you breach the tissue, when you slice it for example, then all of a sudden, very shortly thereafter, you start to cry or produce tears. So it turns out that the onion is able, on demand, to produce an agent that is a lachrymator. And a lachrymator mater is a chemical that induces tears production.
MARC SANCHEZ: That's Professor Rabi Musah. She teaches chemistry at the State University of New York at Albany. And she knows about lachrymators because she studies the ways in which plants use chemicals to defend themselves. And the thing that's happening in an onion that makes us cry is one of these defense mechanisms.
When you cut into the skin of an onion, it sets off a pretty cool chain of events. Inside every onion, there's a molecule called isoalliin. It's always there, even at the grocery store. When an onion is sliced, the cell that contains isoalliin opens up. Next, isoalliin quickly comes in contact with an enzyme called alliinase. And when isoalliin and alliinase meet, isoalliin is transformed into a new type of molecule called a sulfenic acid.
RABI MUSAH: But that's not what makes you cry-- it's not the sulfenic acid. The sulfenic acid gets converted by a second enzyme--
MARC SANCHEZ: The lachrymatory factor synthase, or we can make it easier and call it LFS. That's what most people do. Sulfenic acid combines with the LFS enzyme, which produces yet another type of molecule called a sulfine. And it's here that we have our lachrymator, the molecule that irritates our eyes and makes us tear up.
[BABY CRYING]
OK, quick review. Isoalliin is released when we slice an onion. That combines with the enzyme alliinase to form a new molecule called a sulfenic acid, which combines with the LFS enzyme to form another type of molecule called a sulfine and causes our eyes to produce tears.
[BABY CRYING]
Most of us like the flavor onions add to a dish, so we put up with this onion defense mechanism and shed a few tears. But this defense mechanism really works on other animals.
RABI MUSAH: Onions are members of the Allium family of plants.
MARC SANCHEZ: Remember that isoalliin molecule?
RABI MUSAH: Rabbits and things like that, they're not attracted to alliums.
MARC SANCHEZ: Unlike us, animals don't have to cut into the skin of an onion and tear up to know to stay away.
RABI MUSAH: The isoalliin itself interestingly doesn't really have a smell-- at least it doesn't really have a smell that's detectable to humans. But it turns out that there is something that's being produced by the plants before the tissue is breached that alerts deer and other animals to the fact that it's really not going to like the chemicals that are in that plant. And so they don't eat it.
MARC SANCHEZ: Since we do eat it, I wanted to see if there was a way to chop onions without crying. The internet is full of tips for no-tear onion-slicing-- chew gum, hold a piece of bread in your mouth, wear goggles, bite on some matchsticks, freeze the onion, run it underwater, all sorts of stuff. So I wanted to try a few of these out with a professional.
I visited Chef Ann Kim at her restaurant Young Joni in Minneapolis. She also owns a pizza restaurant called Pizzeria Lola. And she told me that between the two restaurants, they go through 50 pounds of onions per week. And popped a couple of matchsticks in her mouth with the tips facing out.
ANN KIM: All right, it's going to be hard to talk, but I'm just going to cut this down. Maybe I'll try dicing this one.
MARC SANCHEZ: OK, yeah, it'll release the lachrymators.
ANN KIM: Yeah, release a little bit-- yes. What'd you call that?
MARC SANCHEZ: Lachrymator.
ANN KIM: Lachrymator?
MARC SANCHEZ: Yeah.
ANN KIM: OK.
[CHOPPING ONIONS]
It's not horrible when I do one onion, but if I do more than one-- but right now, I'm getting no effect.
MARC SANCHEZ: Ann told me that she'd seen one of her chefs trying to match trick before, and it didn't really work for him. But today, maybe. Next, I had an try chopping a yellow onion while chewing on a piece of bread.
ANN KIM: So put the bread in my mouth.
MARC SANCHEZ: Yeah. Just put it in your mouth and--
ANN KIM: OK, I'm not going to talk.
MARC SANCHEZ: You don't have to eat the whole thing.
ANN KIM: OK. [MUFFLING]
MARC SANCHEZ: All right.
[LAUGHTER]
OK, we're dicing this half, a yellow onion.
ANN KIM: Yeah. Are you crying?
MARC SANCHEZ: I'm not crying.
ANN KIM: Wow, OK. I'm actually fine.
MARC SANCHEZ: Still no tears, but it was at this point that I looked around the kitchen. It's a big open space with tall ceilings, and there's an enormous ventilation system sucking out any smoke and bringing fresh air back into the restaurant. This reminded me of another onion chopping trick I read about-- cut your onions by a fan.
I was standing right next to Ann without matches or bread, and I wasn't tearing up either. Maybe Ann's ventilation system was pulling those pesky sulfines away from our eyes. We had one more tip to try, the goggles, and one more onion.
ANN KIM: So red onion, huh?
MARC SANCHEZ: Yeah. It does look a lot nicer.
ANN KIM: Yeah, it's pretty.
MARC SANCHEZ: It is.
ANN KIM: They say for optimum health, you should eat the rainbow, meaning vegetables, colors. Because if you eat things that are just white--
MARC SANCHEZ: Bland.
ANN KIM: --you're eating white bread, sugar, refined things, whereas kale and what-- ooh.
MARC SANCHEZ: Oh, you're getting it already?
ANN KIM: Yeah. Yeah. Whoa! So the goggles worked for the-- yeah. But all of a sudden, yeah, there's something about this red onion that as I was even talking to you and I just sliced in half, I got this whiff of like-- it hit my-- what do you call those glands?
MARC SANCHEZ: Lachrymal glands.
ANN KIM: Try to say that five times really fast.
MARC SANCHEZ: Sure. It's easy. Lachrymal glands.
[LAUGHS]
ANN KIM: So shall I continue slicing?
MARC SANCHEZ: Yeah, let's see. I want to tear up.
ANN KIM: You want to tear up? OK.
[LAUGHS]
[CHOPPING ONIONS]
MARC SANCHEZ: There are a few tips that can help you not to tear up while you slice onions in a non-ventilated area, like your family's kitchen. Make sure your knife is sharp. If not, you'll end up opening more of the cells that release the isoalliin. And running the onions under cold water will help slow down the reaction. Same goes for sticking them in the fridge or freezer for about 15 to 30 minutes before chopping. If you have a tip for no-tear onion-chopping, send it on over to us. We're at hello@brainson.org.
MOLLY BLOOM: Time to mop up those tears and get your ears ready. It's time for the Mystery Sound.
[EERIE SOUND]
SPEAKER: Mystery Sound.
MOLLY BLOOM: Here it is.
[WHINING]
OK. That one's really short, so let's hear it one more time.
[WHINING]
OK Molly, any guesses?
MOLLY: Wow, that's a hard one. So is it like a horse freaking out about something? Or maybe like a chicken?
MOLLY BLOOM: Excellent guess. So you think it's an animal of some sort?
MOLLY: Or maybe it's like turning a faucet that's really squeaky.
MOLLY BLOOM: Ooh, all excellent guesses. We will be back with the answer later in the show.
We are making an episode all about plants, and it got us thinking. What if a plant was running for president? What should the plant presidential campaign slogan be? Maybe something like, you like oxygen? Think outside the boxygen and vote for plants. OK, I'm sure yours will be better than that one. So send them to us at brainson.org/contact.
MOLLY: Your questions and curiosity power Brains On. So if you have a question or a mystery sound or just an idea for us, you can email it to us any time at hello@brainson.org.
MOLLY BLOOM: Just like Quinn, who sent us this question.
QUINN STONE: Why do you sweat when you get nervous?
MOLLY BLOOM: We'll be back with the answer at the end of the show during our Moment of Um. And we'll also have the latest installment of the Brains Honor Roll.
MOLLY: Keep listening. You're listening to Brains On from American Public Media. I'm Molly.
MOLLY BLOOM: And I'm Molly.
SPEAKER: (SINGING) Ooooh, molly-molly, bo-bolly, banana, fanna, fo-folly, me, my mo-molly, molly.
MOLLY BLOOM: OK then.
MOLLY: We're wide awake now and talking all about tears.
MOLLY BLOOM: But what about tears caused by our emotions? Now Molly, you originally got in touch with us about this very topic. What was the question you wrote in with?
MOLLY: Why do your feelings control the amount of water your body gives off? For example, when you're sad, you cry. And when you're nervous, you get sweaty.
MOLLY BLOOM: I love that question. We'll get into the second part of that question about sweat during our Moment of Um at the end of the show. But first, we want to delve into the tears that we produce emotionally.
MOLLY: To find out more about why and how tears are driven by our emotions, we're joined by Lauren Bylsma.
MOLLY BLOOM: She's a clinical psychologist and assistant professor of psychiatry at the University of Pittsburgh.
MOLLY: Why do we produce tears when we're sad and not just vocal cries?
LAUREN BYLSMA: Yeah, that's a really good question. So researchers are really still trying to figure this out. But it's thought that our visible tears evolved from animal vocal cries. So originally, animals had vocal cries to try to get help from their parent or alert others from danger. And then during our evolutionary history, these developed into visible tears.
And it may be because this provided a really good signal to others nearby that someone was in need of help or support but without alerting predators that they're there. Because if you cry, you're more likely to get attacked by some other predator in the environment. And some more recent research has shown that having tears on a sad face-- so if you compare sad faces with and without tears, people are more likely to realize that that person's sad and more likely to feel like they want to help that person.
So it seems that they might have evolved for that reason. And humans too have really complex facial muscles. And when the facial muscles contract when you feel like crying, that might have been what produced the liquid tears at some point in our evolution history.
MOLLY: So do other animals cry?
LAUREN BYLSMA: So other animals have tears to protect their eyes, but it's thought that they don't experience emotional tears. There have been some isolated case studies that some people say mean that other animals cry, like in dogs or elephants or things like that. But these reports haven't been verified scientifically. So if it does occur occasionally in animals, it seems to only be really rare isolated cases and not something that happens on a regular basis.
MOLLY: Mm, that's interesting.
LAUREN BYLSMA: Yeah.
MOLLY: Why do we cry when we feel strong emotions in general, not just sadness?
LAUREN BYLSMA: Yeah, that's a really-- you have a lot of really good questions. So for based on our research, it seems that crying occurs just after the peak of a really intense emotional experience. So it doesn't seem to matter what kind of emotion it is. It could be happy. It could be sad. It could also be other emotions like anger or frustration.
And it seems like the crying might be a way that our body helps us regulate and respond to different types of emotions. So basically, your body gets more arousal right before you cry, which means basically like your heart rate's increasing, you might be breathing more, those kind of things. And then we notice when we're measuring those things when people cry, like right after they cry, those things start to decrease. Like, your heart rate might decrease. Your breathing mate might decrease right after crying.
And then there's also indirect effects, like receiving social support from the environment. So a lot of our research shows that people don't feel better when they cry unless they also are in a supportive social environment. So it could be an indirect effect like you cry. And if you're around supportive people, they see that you're crying and then they comfort you, or they help you deal with whatever the problem is. And your emotions improve as a result.
So there's a couple of different things that could be happening there. And then there's one other part is the cognitive part, which is that when you cry, it forces you to pay attention to the thing that made you cry. And it might help you reach like a new cognitive understanding of that or process your emotions about that. So that could be another way that crying might help.
MOLLY: Why do we get that feeling like a lump in our throat that hurts when we're about to cry?
LAUREN BYLSMA: Part of that is that when our body is having a really intense emotional reaction, we experience an increase of blood flow in our body to help us respond to that and also, an opening of what's called the glottis, which is like where all those vocal folds are in the throat. So this allows our lungs to get more oxygen. And the whole idea is that it is preparing our body to respond to something stressful in the environment.
And feeling like a lump in your throat can also increase because you're trying to hold back your tears. Because then your body is also struggling-- like when you swallow, it's trying to close the glottis, while the rest of your body is trying to open it. So your body is kind of like in a battle with itself. So that could cause that lump-like feeling.
MOLLY: That's really cool-- I didn't know that. Why does pain make us cry? Is it an emotional reaction or a reflex one?
LAUREN BYLSMA: I think we're not entirely sure in the answer, but I think a lot of it has to do with the emotion. So when you're experiencing pain, you might feel really overwhelmed and hopeless. Like, you're unable to make the pain stop. And those type of really intense emotions can cause the crying. But it is possible that there's also a reflex there too. But that hasn't really been studied so we're not really sure if that also plays a role.
MOLLY: What about being tired or exhausted?
LAUREN BYLSMA: So whenever we're really tired or exhausted or if we're just like stressed out or haven't eaten enough those, type of things make us more likely to have really intense emotional reactions. So if you've ever had a night where you didn't get enough sleep, or you didn't get to eat breakfast, maybe you're really like hungry, and then you get more upset. And so we're also more likely to cry in those situations because we're not able to regulate our emotions as well.
MOLLY: Why do newborns not shed tears when they cry?
LAUREN BYLSMA: It has to do with their development. They haven't fully developed their tear ducts yet, so that's why they're not able to have the visible tears yet in the first few weeks. But they do have the vocal cries.
MOLLY: It's completely different from what I thought. That's crazy.
LAUREN BYLSMA: What did you think?
MOLLY: I thought it was something about how they weren't crying for emotions, but more like they were trying just to communicate something.
LAUREN BYLSMA: Yeah. Well, that's a really good idea too. But also, it only takes a few weeks for them to start having the visible tears. And at that point, they're still mostly crying just because they're like, they need to be changed, or they need to eat something or those kind of things. And as we get older, we start crying for different reasons. So that's what little kids cry for.
And then as you get older, maybe you're more likely to cry for things like physical pain when you're a young kid. And then as you get older, maybe things like feeling empathy for others or being sad about things going on in the world, you start having more of those type of crying reactions.
MOLLY: Thank you so much for coming on to the podcast. We really appreciate it.
LAUREN BYLSMA: Thank you, and thank you for all your great questions.
[LOW TEMPO MUSIC]
MOLLY BLOOM: All right, it's time to go back to that mystery sound. Let's hear it again. And this time, it's expanded with something that may help you figure it out.
[WHINING]
Any new guesses?
MOLLY: Is it puppies?
MOLLY BLOOM: What do you think those puppies are doing?
MOLLY: Playing something maybe?
MOLLY BLOOM: Here with the answer is Tamas Farago. He studies animal behavior in Budapest, Hungary. And he specifically studies dogs.
TAMAS FARAGO: So that was a dog whining.
MOLLY BLOOM: Have you ever heard a dog do that before?
MOLLY: No, I haven't.
MOLLY BLOOM: So I've heard it lots of times when my parents' dog is begging for food at the table. That is the sound he makes when he wants food. I've also heard it when you know my friends have left the house and their dogs are whining for them to come back.
MOLLY: Sometimes I make that sound when I want food.
[LAUGHS]
MOLLY BLOOM: Like Lauren talked about earlier, there isn't strong evidence that animals shed tears when they cry. But they do produce vocal cries, like the sound of this dog's whine. When you hear a dog whine, it probably makes you think that it sounds sad. And dogs do make this kind of sound in situations where they are feeling distressed.
TAMAS FARAGO: Mainly, it is linked with negative inner state. So like, in separation or in stressful, anxious situations.
MOLLY BLOOM: But it's also used in other situations too.
TAMAS FARAGO: So originally, when the pups have some problem, they use a whining-like vocalization to get the attention of the mother. And probably, this adult whining is developing from this kind of vocalization. And this these have a really strong attention-getting function. And these really high-pitched sounds are hard to ignore. They also use whining in greeting. Some of the dogs use whining as a begging signal.
MOLLY: There are three kinds of tears-- basal.
MOLLY BLOOM: Those keep your eyes healthy and are present all the time.
MOLLY: Reflex.
MOLLY BLOOM: Those protect your eyes from irritants.
MOLLY: And emotional.
MOLLY BLOOM: The purpose of emotional tears is still a little bit of a mystery.
MOLLY: But they seem to be connected to a feeling of helplessness and desire to be comforted by others.
MOLLY BLOOM: That's it for this episode of Brains On.
MOLLY: Brains On is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: We had production help this week from Lauren Dee, John Lambert, and Eric Fabares.
MOLLY: And engineering help from Shawn Campbell, Corey Schreppel, Johnny Vince-Evans, and Michael Osborne.
MOLLY BLOOM: Many thanks to Blair and Damian Carroll, Steve Martine, Eric Brigham, Nancy Yang, [INAUDIBLE], Chip Walton, Emily Allen, and Anna Reid.
MOLLY: Now before we go, it's time for our Moment of Um.
[VOCALIZING]
QUINN STONE: Hi, my name is Quinn Stone from Sutton, Massachusetts. My question is, why do you sweat when you get nervous?
YANA KAMBEROV: So my name is Yana Kamberov. And I'm an assistant professor in the Department of Genetics at the University of Pennsylvania. We sweat when we get nervous because the part of the brain that senses emotion is largely what's controlling the sweat glands in your palms and in the soles of your feet.
And in part, that has to do, we think, with how sweat glands evolved in the first place, which is when we look at species of animals outside of humans and outside of our closest primate relatives, sweat glands are only found on the palms and the soles of the feet. And there, they serve a role in traction-- so how much contact do you have with the surface that you're walking on?
And you can think about when you're scared, you want to run. You want to run away. You want to have some contact with the surface you're walking on. And imagine if your palms are completely dry and putting your hand across a surface, you're just going to slide off. You need a little bit of liquid there. You need a little bit of water to help you stick, give you a little more traction. Control how much friction you have with the surface you're walking on.
So that might be why we sweat in our palms and the soles of our feet when we get nervous. And actually, that's termed emotional sweating, which is very different in terms of how it's controlled from the sweating that we do when we get hot. It's a controlled by different part of the brain-- by the hypothalamus, which is sensing your core body temperature and your skin temperature.
MOLLY BLOOM: It's no sweat for me to breeze through this list of names. This is the most recent group of kids to be added to the Brain's Honor Roll. They keep this show going with their questions, energy, and ideas.
[LISTING HONOR ROLL]
We'll be back soon with more answers to your questions.
MOLLY: Thanks for listening.
SPEAKER: Brains On is supported in part by a grant from the National Science Foundation.
MOLLY: Molly, I'm here and ready to tape this episode.
MOLLY BLOOM: Oh hey, hang on a sec. I'm just putting the finishing touches on our studio setup. You can have a seat right there.
MOLLY: On this pile of tissue boxes?
MOLLY BLOOM: Yeah.
MOLLY: Where are my headphones?
MOLLY BLOOM: Oh sorry, under the pile of hankies right here. I was going to stuff these all up my sleeves. Do you want some?
MOLLY: Sure. So you're sitting on a pile of tissue boxes too.
MOLLY BLOOM: Mm-hmm.
MOLLY: Oh, and there's more under the table. And are those--
MOLLY BLOOM: More tissues inside the light fixture? Yep. I just wanted to make sure we were prepared for this episode. Questions about tears and crying have been pouring in from our listeners.
LIBBY WANG: Hi, my name is Libby Wang from Moraga, California. I'm here with my brother Elliot.
ELLIOT: Hi.
LIBBY WANG: And my question is, why do tears come out of your eyes when you cry when you are sad?
DYLAN: Hello, my name is Dylan. And I live in Tallahassee, Florida. Why do you cry when you're sometimes very happy, or you're laughing very hard?
DELANEY: My name is Delaney, and I'm from Toronto, Canada. Why does pain make people cry instead of some other physical reaction?
CALEB: Hi, my name is Caleb. I'm from Mountain View, California. And I'm 9 years old. My question is, why do we cry when we're sad?
ELISABETH: My name is Elisabeth from Cincinnati, Ohio. My question is, why do noses get drippy and start getting runny when eyes get wet when I cry?
MOLLY BLOOM: Hang on to your hankies, we're going to answer all those questions right now.
MOLLY: Keep listening. But we're just talking about crying, right? Not actually crying ourselves. Why do you have so many tissues?
MOLLY BLOOM: Uh, they were on sale?
[THEME MUSIC]
You're listening to Brains On from American Public Media. I'm Molly Bloom, and my co-host today is another Molly. Hi, Molly.
MOLLY: Hi, Molly.
MOLLY BLOOM: Hi, Molly.
MOLLY: Hi, Molly.
MOLLY BLOOM: Hi, Molly.
MOLLY: Hi, Molly.
MOLLY BLOOM: Hi, Molly.
[ECHOING]
Molly is 11 years old from Los Angeles. Now Molly, what made you curious about crying in the first place?
MOLLY: So my mom was telling me about this science fiction book, where there was a lot about specifically crying and body moisture. And it just got me thinking about all of that in general.
MOLLY BLOOM: Do you remember the name of the book?
MOLLY: Dune.
MOLLY BLOOM: Oh Dune. So do you feel better after you cry?
MOLLY: Yes, I often do. Sometimes I just feel worse, but usually, I feel much better.
MOLLY BLOOM: And have you also cried when you're happy?
MOLLY: I don't really cry, but tears can definitely come out of my eyes when I'm laughing really hard.
MOLLY BLOOM: Oh yes, I have cried many times from laughing so hard. So why do you think that we cry?
MOLLY: Originally, I thought that we might cry as a way to communicate how we're feeling with people that we know. So like, if we're hurt, and we were having trouble making words, they can tell that we're feeling something because we're crying.
MOLLY BLOOM: That's a really good idea. And what are some times that you have teared up besides when you're sad or hurt?
MOLLY: When I'm really, really tired. I can start sobbing. And it's really annoying because I also like to sleep. And it's kind of hard to cry when you're sleeping.
[LAUGHS]
MOLLY BLOOM: When we cry, we produce tears. And tears are really interesting and also really important.
MOLLY: When you've cried, you've probably asked yourself the same question that was sent to us by Sam in Cheverly, Maryland.
SAM: Why are tears salty?
MOLLY BLOOM: Well, you may have noticed that mucus that comes out of your nose is salty. Blood tastes salty. And sweat is salty.
MOLLY: And that's just because our bodies are pretty salty.
MOLLY BLOOM: Maybe you've heard the word "electrolytes." That's another word for the salt ions that are in our bodies.
MOLLY: Tears come out of your body, so they're salty like us.
MOLLY BLOOM: All tears contain some combination of water, salts, proteins, oil, and mucus. They come from your lachrymal gland.
MOLLY: The lachrymal gland is at the top of your eye. From there, tears move across the cornea or the surface of the eyeball. Then they usually drain at the lachrymal ducts.
MOLLY BLOOM: Those are located in the corner of the eye closest to the nose. In fact, the lachrymal ducts drain into your nose, which explains why your nose runs when you cry. Of course, sometimes you have too many tears to drain, and they spill down your cheeks.
MOLLY: Now you might be thinking, all tears are pretty much the same, right?
MOLLY BLOOM: Not so. There are three distinct types of tears-- basal tears, reflex tears, and emotional tears. They all help with different things.
MOLLY: Like, keeping your eyes moist, and your vision clear.
MOLLY BLOOM: Or defending your peepers from invaders. So how did this trio of terrific tear teammates first team up?
MOLLY: Well, maybe it was something like this.
BASAL TEARS: Hey fellow tears, thanks for meeting me here. As you know, I'm basal tears. You can call me Basal Tears.
REFLEX TEARS: Sure thing. I'm Reflex Tears. Nice to meet you.
EMOTIONAL TEARS: Yeah, I'm Emotional Tears. We saw the ad you posted online, tears needed for a super secret project. Sounds mysterious. I like being mysterious.
TODD: Hey guys, I brought coffee. It's cilantro spiced iced lattes. Yum.
REFLEX TEARS: Cilantro spiced? Is that even a thing?
EMOTIONAL TEARS: Yeah. Sorry Todd, I'm going to have to pass.
BASAL TEARS: Say kid, are you a tear? This is a gathering of tears.
TODD: Well, I'm not a tear yet, but I want to be. Hi, I'm Todd.
BASAL TEARS: Sure. Nice to meet you, [CLEARS THROAT] Todd. Well, let's get started. I'm looking to form a super team of super tears. As you may know, our fair home Eyetropolis is under constant attack.
REFLEX TEARS: Yeah, dust, pollen, that drying heat.
EMOTIONAL TEARS: Not to mention other cities picking on it, making it feel bad-- not cool.
TODD: And fingers. People are always sticking their fingers in Eyetropolis. Right, guys?
BASAL TEARS: Fingers? I guess they could be a problem. Anyway, I want tears with different powers to help protect our precious eyeball home. Now I, Basal Tears, bring a lot to the table. I'm ever-present across the eye. Released in every blink, I keep things moist. I have three layers-- a mucus layer to help my wetness hold on to the eyeball, an aqueous or watery layer that actually moisturizes the eye and protects against invasive bacteria, and a lipid or oily layer.
TODD: I like oil, so slick.
BASAL TEARS: That last layer helps keep the others from evaporating and keeps the surface of the eye smooth so its vision is clear. Obviously, I am most excellent and fantastic at protecting Eyetropolis. But occasionally, I could use some help.
REFLEX TEARS: Oh wow, I've been waiting for this kind of gig. I think I'm your tear. Whenever Eyetropolis is attacked by major irritants like dust clouds or harsh cold winds or Dr. Onion's evil vapors, I flood the place with my reflex tears-- whoosh! They're full of antibodies that fend off evil bacteria. Plus there's usually a lot of them. They flesh things out right away and rehydrate the city-- bada bing, bada boom, reflex tears saves the day.
TODD: Impressive.
EMOTIONAL TEARS: My powers are a little more mysterious. But I think I can really help. My tears come out when the city is feeling upset, harmed, wronged, or even sometimes happy. Whatever the trigger, the city is usually all wound up in some way. It seems I help calm things down. How? My powers are mysterious. Scientists and researchers, even I don't fully understand them.
Also, when I fled the city with my tears it signals to others that we could use some help. Other cities often rally around to comfort us. It helps build bond so we're stronger in the future. It's a mystical ancient power that I think could help your team.
BASAL TEARS: Most intriguing. Yes, I think you'll fit right in, Emotional Tears.
TODD: Well guys, I'm not a tear, but maybe I could be. Like, what if I squirted out of the eye like a water pistol? [LAUGHS] You know, shooting a stream of tears at our enemies like a salty fire hose, that'll teach them.
REFLEX TEARS: Huh?
EMOTIONAL TEARS: Huh? That's weird, Todd.
BASAL TEARS: Yeah, that's not really what I'm looking for.
TODD: OK, how about I'm like a hard tear. Like, I come out all rough like a diamond. What's up, enemies? You can't hurt me.
REFLEX TEARS: Are you crazy? That would scratch that metropolis cornea. No way.
BASAL TEARS: You know, maybe we're best as a trio-- basil tears, reflex tears, and emotional tears. Protecting Eyetropolis together!
ALL: Yeah!
BASAL TEARS: Flushing out evil in the blink of an eye, the three muske-tears!
EMOTIONAL TEARS: Sounds good.
REFLEX TEARS: Right on!
TODD: And their sidekick Todd, the neon yellow tear.
BASAL TEARS: Uh, no.
TODD: Todd, the burning tear made of peppers.
EMOTIONAL TEARS: Why would you even?
TODD: The stinky tear-- you can smell me coming from a mile away.
REFLEX TEARS: Just stop.
TODD: The cheer tear-- I come out with pom-poms, and I do the splits.
BASAL TEARS: You know Todd, maybe you should try a different city, perhaps Noseville could use someone with your creativity.
TODD: Noseville? Yeah. I could be a booger. Todd, the school bus booger. I'm there when you're riding the bus, and you need to flick something at that person.
BASAL TEARS: Sure, sure. We've got some planning to do. So why don't you run off to Noseville now and offer your services? In the meantime, tears--
ALL: Let's protect Eyetropolis!
[TRIUMPHANT MUSIC]
MOLLY BLOOM: So there are three types of tears-- basal, reflex, and emotional.
MOLLY: Basal tears are in your eyes all the time.
MOLLY BLOOM: But reflex tears need to be triggered by something. And there's one trigger in particular that our listeners are really, really curious about.
HENRY: My name is Henry from Maple Grove, Minnesota. And my question is, why do onions make you cry?
JOSEPH: Hello, my name is Joseph. I am from Ireland. And my question is, why do onions make you cry?
MOLLY: Brains On producer Marc Sanchez is here with an answer.
MARC SANCHEZ: Ever wonder how the produce section of the grocery store can have a mound of onions but nobody in the store is crying?
RABI MUSAH: If you just hold an onion, you don't cry you don't produce tears. But when you breach the tissue, when you slice it for example, then all of a sudden, very shortly thereafter, you start to cry or produce tears. So it turns out that the onion is able, on demand, to produce an agent that is a lachrymator. And a lachrymator mater is a chemical that induces tears production.
MARC SANCHEZ: That's Professor Rabi Musah. She teaches chemistry at the State University of New York at Albany. And she knows about lachrymators because she studies the ways in which plants use chemicals to defend themselves. And the thing that's happening in an onion that makes us cry is one of these defense mechanisms.
When you cut into the skin of an onion, it sets off a pretty cool chain of events. Inside every onion, there's a molecule called isoalliin. It's always there, even at the grocery store. When an onion is sliced, the cell that contains isoalliin opens up. Next, isoalliin quickly comes in contact with an enzyme called alliinase. And when isoalliin and alliinase meet, isoalliin is transformed into a new type of molecule called a sulfenic acid.
RABI MUSAH: But that's not what makes you cry-- it's not the sulfenic acid. The sulfenic acid gets converted by a second enzyme--
MARC SANCHEZ: The lachrymatory factor synthase, or we can make it easier and call it LFS. That's what most people do. Sulfenic acid combines with the LFS enzyme, which produces yet another type of molecule called a sulfine. And it's here that we have our lachrymator, the molecule that irritates our eyes and makes us tear up.
[BABY CRYING]
OK, quick review. Isoalliin is released when we slice an onion. That combines with the enzyme alliinase to form a new molecule called a sulfenic acid, which combines with the LFS enzyme to form another type of molecule called a sulfine and causes our eyes to produce tears.
[BABY CRYING]
Most of us like the flavor onions add to a dish, so we put up with this onion defense mechanism and shed a few tears. But this defense mechanism really works on other animals.
RABI MUSAH: Onions are members of the Allium family of plants.
MARC SANCHEZ: Remember that isoalliin molecule?
RABI MUSAH: Rabbits and things like that, they're not attracted to alliums.
MARC SANCHEZ: Unlike us, animals don't have to cut into the skin of an onion and tear up to know to stay away.
RABI MUSAH: The isoalliin itself interestingly doesn't really have a smell-- at least it doesn't really have a smell that's detectable to humans. But it turns out that there is something that's being produced by the plants before the tissue is breached that alerts deer and other animals to the fact that it's really not going to like the chemicals that are in that plant. And so they don't eat it.
MARC SANCHEZ: Since we do eat it, I wanted to see if there was a way to chop onions without crying. The internet is full of tips for no-tear onion-slicing-- chew gum, hold a piece of bread in your mouth, wear goggles, bite on some matchsticks, freeze the onion, run it underwater, all sorts of stuff. So I wanted to try a few of these out with a professional.
I visited Chef Ann Kim at her restaurant Young Joni in Minneapolis. She also owns a pizza restaurant called Pizzeria Lola. And she told me that between the two restaurants, they go through 50 pounds of onions per week. And popped a couple of matchsticks in her mouth with the tips facing out.
ANN KIM: All right, it's going to be hard to talk, but I'm just going to cut this down. Maybe I'll try dicing this one.
MARC SANCHEZ: OK, yeah, it'll release the lachrymators.
ANN KIM: Yeah, release a little bit-- yes. What'd you call that?
MARC SANCHEZ: Lachrymator.
ANN KIM: Lachrymator?
MARC SANCHEZ: Yeah.
ANN KIM: OK.
[CHOPPING ONIONS]
It's not horrible when I do one onion, but if I do more than one-- but right now, I'm getting no effect.
MARC SANCHEZ: Ann told me that she'd seen one of her chefs trying to match trick before, and it didn't really work for him. But today, maybe. Next, I had an try chopping a yellow onion while chewing on a piece of bread.
ANN KIM: So put the bread in my mouth.
MARC SANCHEZ: Yeah. Just put it in your mouth and--
ANN KIM: OK, I'm not going to talk.
MARC SANCHEZ: You don't have to eat the whole thing.
ANN KIM: OK. [MUFFLING]
MARC SANCHEZ: All right.
[LAUGHTER]
OK, we're dicing this half, a yellow onion.
ANN KIM: Yeah. Are you crying?
MARC SANCHEZ: I'm not crying.
ANN KIM: Wow, OK. I'm actually fine.
MARC SANCHEZ: Still no tears, but it was at this point that I looked around the kitchen. It's a big open space with tall ceilings, and there's an enormous ventilation system sucking out any smoke and bringing fresh air back into the restaurant. This reminded me of another onion chopping trick I read about-- cut your onions by a fan.
I was standing right next to Ann without matches or bread, and I wasn't tearing up either. Maybe Ann's ventilation system was pulling those pesky sulfines away from our eyes. We had one more tip to try, the goggles, and one more onion.
ANN KIM: So red onion, huh?
MARC SANCHEZ: Yeah. It does look a lot nicer.
ANN KIM: Yeah, it's pretty.
MARC SANCHEZ: It is.
ANN KIM: They say for optimum health, you should eat the rainbow, meaning vegetables, colors. Because if you eat things that are just white--
MARC SANCHEZ: Bland.
ANN KIM: --you're eating white bread, sugar, refined things, whereas kale and what-- ooh.
MARC SANCHEZ: Oh, you're getting it already?
ANN KIM: Yeah. Yeah. Whoa! So the goggles worked for the-- yeah. But all of a sudden, yeah, there's something about this red onion that as I was even talking to you and I just sliced in half, I got this whiff of like-- it hit my-- what do you call those glands?
MARC SANCHEZ: Lachrymal glands.
ANN KIM: Try to say that five times really fast.
MARC SANCHEZ: Sure. It's easy. Lachrymal glands.
[LAUGHS]
ANN KIM: So shall I continue slicing?
MARC SANCHEZ: Yeah, let's see. I want to tear up.
ANN KIM: You want to tear up? OK.
[LAUGHS]
[CHOPPING ONIONS]
MARC SANCHEZ: There are a few tips that can help you not to tear up while you slice onions in a non-ventilated area, like your family's kitchen. Make sure your knife is sharp. If not, you'll end up opening more of the cells that release the isoalliin. And running the onions under cold water will help slow down the reaction. Same goes for sticking them in the fridge or freezer for about 15 to 30 minutes before chopping. If you have a tip for no-tear onion-chopping, send it on over to us. We're at hello@brainson.org.
MOLLY BLOOM: Time to mop up those tears and get your ears ready. It's time for the Mystery Sound.
[EERIE SOUND]
SPEAKER: Mystery Sound.
MOLLY BLOOM: Here it is.
[WHINING]
OK. That one's really short, so let's hear it one more time.
[WHINING]
OK Molly, any guesses?
MOLLY: Wow, that's a hard one. So is it like a horse freaking out about something? Or maybe like a chicken?
MOLLY BLOOM: Excellent guess. So you think it's an animal of some sort?
MOLLY: Or maybe it's like turning a faucet that's really squeaky.
MOLLY BLOOM: Ooh, all excellent guesses. We will be back with the answer later in the show.
We are making an episode all about plants, and it got us thinking. What if a plant was running for president? What should the plant presidential campaign slogan be? Maybe something like, you like oxygen? Think outside the boxygen and vote for plants. OK, I'm sure yours will be better than that one. So send them to us at brainson.org/contact.
MOLLY: Your questions and curiosity power Brains On. So if you have a question or a mystery sound or just an idea for us, you can email it to us any time at hello@brainson.org.
MOLLY BLOOM: Just like Quinn, who sent us this question.
QUINN STONE: Why do you sweat when you get nervous?
MOLLY BLOOM: We'll be back with the answer at the end of the show during our Moment of Um. And we'll also have the latest installment of the Brains Honor Roll.
MOLLY: Keep listening. You're listening to Brains On from American Public Media. I'm Molly.
MOLLY BLOOM: And I'm Molly.
SPEAKER: (SINGING) Ooooh, molly-molly, bo-bolly, banana, fanna, fo-folly, me, my mo-molly, molly.
MOLLY BLOOM: OK then.
MOLLY: We're wide awake now and talking all about tears.
MOLLY BLOOM: But what about tears caused by our emotions? Now Molly, you originally got in touch with us about this very topic. What was the question you wrote in with?
MOLLY: Why do your feelings control the amount of water your body gives off? For example, when you're sad, you cry. And when you're nervous, you get sweaty.
MOLLY BLOOM: I love that question. We'll get into the second part of that question about sweat during our Moment of Um at the end of the show. But first, we want to delve into the tears that we produce emotionally.
MOLLY: To find out more about why and how tears are driven by our emotions, we're joined by Lauren Bylsma.
MOLLY BLOOM: She's a clinical psychologist and assistant professor of psychiatry at the University of Pittsburgh.
MOLLY: Why do we produce tears when we're sad and not just vocal cries?
LAUREN BYLSMA: Yeah, that's a really good question. So researchers are really still trying to figure this out. But it's thought that our visible tears evolved from animal vocal cries. So originally, animals had vocal cries to try to get help from their parent or alert others from danger. And then during our evolutionary history, these developed into visible tears.
And it may be because this provided a really good signal to others nearby that someone was in need of help or support but without alerting predators that they're there. Because if you cry, you're more likely to get attacked by some other predator in the environment. And some more recent research has shown that having tears on a sad face-- so if you compare sad faces with and without tears, people are more likely to realize that that person's sad and more likely to feel like they want to help that person.
So it seems that they might have evolved for that reason. And humans too have really complex facial muscles. And when the facial muscles contract when you feel like crying, that might have been what produced the liquid tears at some point in our evolution history.
MOLLY: So do other animals cry?
LAUREN BYLSMA: So other animals have tears to protect their eyes, but it's thought that they don't experience emotional tears. There have been some isolated case studies that some people say mean that other animals cry, like in dogs or elephants or things like that. But these reports haven't been verified scientifically. So if it does occur occasionally in animals, it seems to only be really rare isolated cases and not something that happens on a regular basis.
MOLLY: Mm, that's interesting.
LAUREN BYLSMA: Yeah.
MOLLY: Why do we cry when we feel strong emotions in general, not just sadness?
LAUREN BYLSMA: Yeah, that's a really-- you have a lot of really good questions. So for based on our research, it seems that crying occurs just after the peak of a really intense emotional experience. So it doesn't seem to matter what kind of emotion it is. It could be happy. It could be sad. It could also be other emotions like anger or frustration.
And it seems like the crying might be a way that our body helps us regulate and respond to different types of emotions. So basically, your body gets more arousal right before you cry, which means basically like your heart rate's increasing, you might be breathing more, those kind of things. And then we notice when we're measuring those things when people cry, like right after they cry, those things start to decrease. Like, your heart rate might decrease. Your breathing mate might decrease right after crying.
And then there's also indirect effects, like receiving social support from the environment. So a lot of our research shows that people don't feel better when they cry unless they also are in a supportive social environment. So it could be an indirect effect like you cry. And if you're around supportive people, they see that you're crying and then they comfort you, or they help you deal with whatever the problem is. And your emotions improve as a result.
So there's a couple of different things that could be happening there. And then there's one other part is the cognitive part, which is that when you cry, it forces you to pay attention to the thing that made you cry. And it might help you reach like a new cognitive understanding of that or process your emotions about that. So that could be another way that crying might help.
MOLLY: Why do we get that feeling like a lump in our throat that hurts when we're about to cry?
LAUREN BYLSMA: Part of that is that when our body is having a really intense emotional reaction, we experience an increase of blood flow in our body to help us respond to that and also, an opening of what's called the glottis, which is like where all those vocal folds are in the throat. So this allows our lungs to get more oxygen. And the whole idea is that it is preparing our body to respond to something stressful in the environment.
And feeling like a lump in your throat can also increase because you're trying to hold back your tears. Because then your body is also struggling-- like when you swallow, it's trying to close the glottis, while the rest of your body is trying to open it. So your body is kind of like in a battle with itself. So that could cause that lump-like feeling.
MOLLY: That's really cool-- I didn't know that. Why does pain make us cry? Is it an emotional reaction or a reflex one?
LAUREN BYLSMA: I think we're not entirely sure in the answer, but I think a lot of it has to do with the emotion. So when you're experiencing pain, you might feel really overwhelmed and hopeless. Like, you're unable to make the pain stop. And those type of really intense emotions can cause the crying. But it is possible that there's also a reflex there too. But that hasn't really been studied so we're not really sure if that also plays a role.
MOLLY: What about being tired or exhausted?
LAUREN BYLSMA: So whenever we're really tired or exhausted or if we're just like stressed out or haven't eaten enough those, type of things make us more likely to have really intense emotional reactions. So if you've ever had a night where you didn't get enough sleep, or you didn't get to eat breakfast, maybe you're really like hungry, and then you get more upset. And so we're also more likely to cry in those situations because we're not able to regulate our emotions as well.
MOLLY: Why do newborns not shed tears when they cry?
LAUREN BYLSMA: It has to do with their development. They haven't fully developed their tear ducts yet, so that's why they're not able to have the visible tears yet in the first few weeks. But they do have the vocal cries.
MOLLY: It's completely different from what I thought. That's crazy.
LAUREN BYLSMA: What did you think?
MOLLY: I thought it was something about how they weren't crying for emotions, but more like they were trying just to communicate something.
LAUREN BYLSMA: Yeah. Well, that's a really good idea too. But also, it only takes a few weeks for them to start having the visible tears. And at that point, they're still mostly crying just because they're like, they need to be changed, or they need to eat something or those kind of things. And as we get older, we start crying for different reasons. So that's what little kids cry for.
And then as you get older, maybe you're more likely to cry for things like physical pain when you're a young kid. And then as you get older, maybe things like feeling empathy for others or being sad about things going on in the world, you start having more of those type of crying reactions.
MOLLY: Thank you so much for coming on to the podcast. We really appreciate it.
LAUREN BYLSMA: Thank you, and thank you for all your great questions.
[LOW TEMPO MUSIC]
MOLLY BLOOM: All right, it's time to go back to that mystery sound. Let's hear it again. And this time, it's expanded with something that may help you figure it out.
[WHINING]
Any new guesses?
MOLLY: Is it puppies?
MOLLY BLOOM: What do you think those puppies are doing?
MOLLY: Playing something maybe?
MOLLY BLOOM: Here with the answer is Tamas Farago. He studies animal behavior in Budapest, Hungary. And he specifically studies dogs.
TAMAS FARAGO: So that was a dog whining.
MOLLY BLOOM: Have you ever heard a dog do that before?
MOLLY: No, I haven't.
MOLLY BLOOM: So I've heard it lots of times when my parents' dog is begging for food at the table. That is the sound he makes when he wants food. I've also heard it when you know my friends have left the house and their dogs are whining for them to come back.
MOLLY: Sometimes I make that sound when I want food.
[LAUGHS]
MOLLY BLOOM: Like Lauren talked about earlier, there isn't strong evidence that animals shed tears when they cry. But they do produce vocal cries, like the sound of this dog's whine. When you hear a dog whine, it probably makes you think that it sounds sad. And dogs do make this kind of sound in situations where they are feeling distressed.
TAMAS FARAGO: Mainly, it is linked with negative inner state. So like, in separation or in stressful, anxious situations.
MOLLY BLOOM: But it's also used in other situations too.
TAMAS FARAGO: So originally, when the pups have some problem, they use a whining-like vocalization to get the attention of the mother. And probably, this adult whining is developing from this kind of vocalization. And this these have a really strong attention-getting function. And these really high-pitched sounds are hard to ignore. They also use whining in greeting. Some of the dogs use whining as a begging signal.
MOLLY: There are three kinds of tears-- basal.
MOLLY BLOOM: Those keep your eyes healthy and are present all the time.
MOLLY: Reflex.
MOLLY BLOOM: Those protect your eyes from irritants.
MOLLY: And emotional.
MOLLY BLOOM: The purpose of emotional tears is still a little bit of a mystery.
MOLLY: But they seem to be connected to a feeling of helplessness and desire to be comforted by others.
MOLLY BLOOM: That's it for this episode of Brains On.
MOLLY: Brains On is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: We had production help this week from Lauren Dee, John Lambert, and Eric Fabares.
MOLLY: And engineering help from Shawn Campbell, Corey Schreppel, Johnny Vince-Evans, and Michael Osborne.
MOLLY BLOOM: Many thanks to Blair and Damian Carroll, Steve Martine, Eric Brigham, Nancy Yang, [INAUDIBLE], Chip Walton, Emily Allen, and Anna Reid.
MOLLY: Now before we go, it's time for our Moment of Um.
[VOCALIZING]
QUINN STONE: Hi, my name is Quinn Stone from Sutton, Massachusetts. My question is, why do you sweat when you get nervous?
YANA KAMBEROV: So my name is Yana Kamberov. And I'm an assistant professor in the Department of Genetics at the University of Pennsylvania. We sweat when we get nervous because the part of the brain that senses emotion is largely what's controlling the sweat glands in your palms and in the soles of your feet.
And in part, that has to do, we think, with how sweat glands evolved in the first place, which is when we look at species of animals outside of humans and outside of our closest primate relatives, sweat glands are only found on the palms and the soles of the feet. And there, they serve a role in traction-- so how much contact do you have with the surface that you're walking on?
And you can think about when you're scared, you want to run. You want to run away. You want to have some contact with the surface you're walking on. And imagine if your palms are completely dry and putting your hand across a surface, you're just going to slide off. You need a little bit of liquid there. You need a little bit of water to help you stick, give you a little more traction. Control how much friction you have with the surface you're walking on.
So that might be why we sweat in our palms and the soles of our feet when we get nervous. And actually, that's termed emotional sweating, which is very different in terms of how it's controlled from the sweating that we do when we get hot. It's a controlled by different part of the brain-- by the hypothalamus, which is sensing your core body temperature and your skin temperature.
MOLLY BLOOM: It's no sweat for me to breeze through this list of names. This is the most recent group of kids to be added to the Brain's Honor Roll. They keep this show going with their questions, energy, and ideas.
[LISTING HONOR ROLL]
We'll be back soon with more answers to your questions.
MOLLY: Thanks for listening.
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