Do plants have feelings?

DARSHANA: You're listening to Brains On where we're serious about being curious.

CHILD 1: Brains On is supported in part by a grant from the National Science Foundation.

REPORTER: Breaking news, in a surprising upset, a dark horse candidate has taken the lead in the presidential race. Apparently, it's a plant? OK. Well, let's hear what supporters are saying.

SUPPORTER 1: You know, I appreciate that plants are all about growth. That's what our country needs.

SUPPORTER 2: I like that the plant doesn't give big, long speeches or any speeches. It's the strong, silent type.

SUPPORTER 3: I like a politician who can throw shade. And boy, does plant throw shade.

SUPPORTER 4: Plant is constantly absorbing carbon dioxide which helps fight global warming, so yeah, it's got my vote.

SUPPORTER 5: I don't know. I just like its vibe and also its flowers.

REPORTER: There you have it. Second-place candidate Preston Peters had this to say in response.

PRESTON PETERS: I'm losing to a plant? How is that even possible? Like, with leaves and everything? Gah, I need to rethink my life choices.

REPORTER: We'll be back with more on this story as it develops. Until then, here's Brains On.

[THEME MUSIC]

MOLLY BLOOM: You're listening to Brains On from American Public Media. I'm Molly Bloom, and my cohost for this episode is Darshana from Oaklyn, California. Hi, Darshana.

DARSHANA: Hi. I'm the obsessed plant person you've all been looking for right here, right now.

MOLLY BLOOM: Well, we are so glad to have found you. What is it that makes you so obsessed about plants?

DARSHANA: I have a greenhouse. I love plants. I talk to them. Yes, I know it's weird. Yeah. It's really fun.

MOLLY BLOOM: What do you say to the plants?

DARSHANA: I kind of just say, good morning. How are you doing? You're looking good today. Stuff like that.

MOLLY BLOOM: That's so awesome. And so tell me a little bit about your plant routine. Do you go out there every day? How do you take care of them?

DARSHANA: Sometimes I plant some things, like once a month, because-- that sounds not a lot of planting, but I need to get the ones that I planted before sprouting until I plant the next ones. And so on weekends, I go in the morning to water them. And on weekdays, I go at night.

MOLLY BLOOM: And what kinds of plants do you have in the greenhouse?

DARSHANA: I mostly have flowers, but I also have cat grass, which is basically catnip cats can eat.

MOLLY BLOOM: Do you have a favorite?

DARSHANA: Sunflowers, the really tall ones. And now they're famous on our block. Every year, we grow them, and everybody's like, oh, you're going to do sunflowers this year? They were so pretty, blah, blah, blah.

MOLLY BLOOM: So those grow outside of the greenhouse?

DARSHANA: They grow in the front yard. So it's yard, sidewalk, and then we have that little dirt area, and we grow it there.

MOLLY BLOOM: How does it make you feel when you see those sunflowers over the summer?

- I feel really happy, and there's one that's always at least taller than my mom.

- Oh, wow.

- And I like to see them bloom and stuff.

- Well, Darshana, we asked you to help us out today not because of your garden but because you asked us a really good question.

DARSHANA: Do plants have feelings?

MOLLY BLOOM: So what made you think of this question? It's such a good one.

DARSHANA: I was kind of just talking to my plants, being like, hey there, hi, y'all. And then I was like, can they hear me? What do they think if they can hear me? Are they happy to see me? But they don't have eyes.

MOLLY BLOOM: So what do you think? Do you think plants can sort of think and feel the way that we can?

DARSHANA: I know it's not backed up by science, and this is a science podcast, but I kind of feel like they do have feelings-- not the way that we could because we can't define feelings. There's so many of them. But it's like, maybe they feel better some days and not better or worse some days. And maybe they're not happy to see because they don't have eyes but hear their friends, you know?

MOLLY BLOOM: Mm-hmm. Well, yeah. I mean, there are things that are good for plants and things that aren't good for plants.

DARSHANA: Yeah. So maybe when they get eaten, they don't like that. That's a feeling, not liking stuff.

MOLLY BLOOM: Well, we asked Sanden to look into this, and--

SANDEN TOTTEN: Here I am. Oh. Ah, that was heavy.

MOLLY BLOOM: Hey, Sanden.

DARSHANA: Is that a bag of soil?

SANDEN TOTTEN: Of course, it is. Now, take off your shoes.

MOLLY BLOOM: OK, but--

SANDEN TOTTEN: Socks too, come on. Chop chop.

DARSHANA: Wait. Why are we doing this?

SANDEN TOTTEN: You're right. This is fun.

MOLLY BLOOM: Sometimes I don't think he listens.

SANDEN TOTTEN: Now, hold your feet still while I pour some fresh dirt on them.

[POURING SOIL]

Nice. And a sprinkle of water.

[WATERING SOIL]

There! How does that feel?

DARSHANA: Squishy, and it feels like there's worms in it.

MOLLY BLOOM: Yeah. It also feels like you made a huge mess in the studio.

SANDEN TOTTEN: Exactly. It feels like you're a plant.

DARSHANA: OK, I guess.

SANDEN TOTTEN: I wanted you both to be in a planting mindset for this episode. Now, make sure you absorb plenty of water and nutrients through your feet--

MOLLY BLOOM: Not possible.

SANDEN TOTTEN: --while I take you on a journey through the world of plants. Darshana, your question about plant feelings brings up a whole mess of other questions like, what do we mean by feelings? And how would we even know what plants are experiencing anyway? And honestly, can we even define what we are experiencing? What is our consciousness, and what are our feelings? Darshana, how would you define feelings, like if you had to explain them to an alien or a robot?

DARSHANA: Feelings are not very explainable. But if I had to, happy, for example, sometimes you feel it when you get something you want or like you're walking on air. A robot would probably take the walking on air part the wrong way, but--

SANDEN TOTTEN: Right, yeah.

MOLLY BLOOM: Yeah, they are really hard to describe.

SANDEN TOTTEN: Well, to investigate this plant feeling question, let's start small and work our way up because it is a tricky topic. Lucky for us, the last 10 years or so are chock-full of well-established plant science that we can turn to. But before we get to that, let's talk about some not-so-well-established plant science and the best-selling book called The Secret Life of Plants.

[MUSIC PLAYING]

The year was 1973. US President Richard Nixon was getting tangled up in a political scandal called Watergate. NASA wrapped up its last moon landing. And back here on Earth, hippies roamed the streets dressed in bell bottoms and floral prints, saying stuff like--

WOMAN: Far out, man.

SANDEN TOTTEN: --and--

MAN: Keep on trucking.

SANDEN TOTTEN: This was way before computers and the internet really took off, so people listened to music on big black records. They watched TV shows on TVs with antennas. And they read lots of books, including one called The Secret Life of Plants, and it was full of far-out facts.

WOMAN: Hey, man. Did you know plants prefer classical music to rock and roll? Unreal.

MAN: Yeah. And it says here, plants hate violence. I also hate violence. So groovy.

SANDEN TOTTEN: A lot of the book is based on a series of studies where a researcher hooked up plants to a lie detector. Now, do you know what those machines are, Darshana?

DARSHANA: Yeah. They're kind of like-- you hook them up to your fingers, and you tell a lie or not a lie. And it beeps red if it was a lie and green if it's not. But usually they don't work.

[LAUGHS]

SANDEN TOTTEN: Right. So these machines, they have sensors, and you put them on a person, and it'll measure electrical activity. Normally, you'd put the sensors on a person and ask them questions, but one researcher hooked up his plants to this machine. Then he would do stuff and see if the plants responded with an electrical pulse. And according to him, the plants totally responded.

If someone hurt a plant, the plant would react. If someone hurt an animal near the plant, the plant would react. In fact, if someone just thought about hurting a plant, the plant would react.

WOMAN: It's like plants are totally psychic. They can read our minds.

MAN: Whoa! Out of sight. Plants are so sensitive. They totally have feelings, man.

SANDEN TOTTEN: Hold up, hippies. The book might have been a hit, but the claims in it, not so much.

WOMAN: Wait, what?

MAN: What?

HEIDI APPEL: I thought it was wildly interesting, but then-- I wasn't even a scientist then, but then I started going, really?

SANDEN TOTTEN: That's Heidi Appel. Today she's a professor at the University of Toledo, but back in the '70s, she was a teenager who was fascinated by plants and this weird plant book.

HEIDI APPEL: And the more I read, the more I realized that a lot of the stuff that was published in there was completely wacko. But because I loved plants, it didn't deter me from becoming a biologist who then returned years later to the kinds of questions that were posed in that Life of Plants.

SANDEN TOTTEN: Heidi wasn't the only one who thought this book was a bit batty. Other scientists tried to repeat the lie detector tests, and-- surprise-- they didn't work. Even though the book and its claims were shown to be wrong, some of it stayed in people's minds.

MOLLY BLOOM: Like the part about plants liking classical music, I'm pretty sure I heard that growing up.

SANDEN TOTTEN: Exactly. Now, the process of science did what it was supposed to. Researchers saw wild claims. They tested them. And when they couldn't repeat them, the claims were thrown out.

DARSHANA: Science is so groovy.

SANDEN TOTTEN: Totally out of sight, yeah, but this book left kind of a stain on the world of plant science for a while. Some people started associating plant research with this kind of unscientific worldview. And Heidi Appel says, because of that, for years, there wasn't as much new plant science being done.

HEIDI APPEL: I mean, there were still some scientists who proceeded with research in this area, and that was great, but it definitely slowed down research in the area.

[MUSIC PLAYING]

SANDEN TOTTEN: But eventually, like plants awakening in the spring, this field of research started blooming again. Amazing discoveries were made about plants hearing, even communicating. And this time, it was all backed by solid science, and I'll tell you about it coming up.

MOLLY BLOOM: Wow, I am very excited to hear the next chapter. But first, Sanden, please help us clean up all this mud.

DARSHANA: Yeah. And I really need to wash my feet.

SANDEN TOTTEN: Uh, yeah. You know, now that I have time to reflect on it, this might not have been the best decision I've made today. Let me go get a shovel.

[MUSIC PLAYING]

MOLLY BLOOM: While Sanden is cleaning the studio floor, let's move things along with a--

CHILD 2: (WHISPERING) Mystery sound.

MOLLY BLOOM: Here it is.

[MYSTERY SOUND]

What is your guess, Darshana?

DARSHANA: Kind of feels like-- I have one of these in a museum. If you push your hand into it, the other side has your handprint. It kind of sounds like that.

MOLLY BLOOM: Oh, yeah, like those things that have the little metal pins, and you can put your hand, and it makes an impression of them?

DARSHANA: Yeah. Or maybe it's something to do with plants. If that is, it might have been, I don't know, plants. I don't know.

MOLLY BLOOM: Well, we're going to give you another chance to hear it and guess a little bit later in the show.

[MUSIC PLAYING]

DARSHANA: Do you have a question for the show or a mystery sound you want to share?

MOLLY BLOOM: Maybe a drawing of a plant-for-president poster?

DARSHANA: That would be awesome. Send it to us at brainson.org/contact.

MOLLY BLOOM: That's how we got this brain-busting question.

[? CHIARA: ?] Hi. My name is [? Chiara. ?] I am seven years old. And my question is, why do bats sleep upside down?

MOLLY BLOOM: We'll answer that at the end of the show. Plus, you'll hear the latest group of kids to join the Brain's Honor Roll.

DARSHANA: Keep listening.

MOLLY BLOOM: You're listening to Brains On. I'm Molly.

DARSHANA: And I'm Darshana.

MOLLY BLOOM: Here at Brains On, we love plants. We think they have a lot to share with the world.

DARSHANA: That's why we wanted to imagine a world where plants could run for president.

MOLLY BLOOM: Obviously, any plant candidate, or plantidate, would need a good slogan.

DARSHANA: And wow, you all had some amazing ideas.

CHILD 3: Hi. My plant-for-president slogan is, "A vote for me is a vote for sustainability."

CHILD 4: My idea for a plant slogan is, "A photosynthe-myth you can believe in."

CHILD 5: "Be-leaf in me so we grow together as a country."

CHILD 6: My name is Mr. Plant, and I'm running for president. I will stop global warming, or else I will die. Please vote for me. Thank you.

CHILD 7: My idea for the plants campaign slogan is, "Plant your vote my way."

CHILD 8: If plants were running for president, they would say, "Please pick me. I planted my roots."

CHILD 9: My slogan is, "I never leaf anybody out."

CHILD 10: Hi, Brains On. We have a plant slogan for you.

CHILD 11: "Laying down roots for a plantastic environment. With your vote, we believe we can do anything!"

MOLLY BLOOM: It's going to be a tough race in this plant presidential election. Thanks to Riley from Melbourne, [? Ellia ?] from Phoenix, Elliot from Toronto, Daniel from Rockport, Maine, Min from Sydney, Elias from Durham, North Carolina, Greta and Maya from Chicago, and Jackson. Darshana, do you have a plant-for-president slogan you want to share?

DARSHANA: Sure. "You usually plant me, but this time, I'm going to plant something. I'm going to plant some new laws."

MOLLY BLOOM: [LAUGHS]

SANDEN TOTTEN: Wow, rousing stuff, really inspiring. Plants have my vote.

DARSHANA: Welcome back, Sanden.

SANDEN TOTTEN: Thanks. So when we left off, the world of plant science was recovering from some bogus claims that put the brakes on new research during the 1970s and 1980s. But eventually, things picked up. Remember that scientist we heard from before, Heidi Appel?

MOLLY BLOOM: Yeah, the researcher from University of Toledo.

SANDEN TOTTEN: Right, who has an excellent name for studying plants, by the way. People like her were doing new exciting studies. She started at a new university, and she was talking with a colleague who studied how insects communicate on plants. Now, his team needed to monitor these tiny sounds, so they measured the vibrations they cause in leaves.

HEIDI APPEL: And then he said, but we had a terrible day today because there was a caterpillar chewing on the plant, and we couldn't hear anything else. And at that point, we both looked at each other and thought the same thing.

SANDEN TOTTEN: They thought, could the plant also be hearing this noisy caterpillar?

MOLLY BLOOM: Wait. Plants hearing? They don't have ears.

SANDEN TOTTEN: That is a very good point, Molly, very good observation. They do not, but they do have these special proteins in their cells that can detect pressure on them, which is kind of like how our eardrums detect pressure from sound waves. Heidi knew this, and she knew that when a caterpillar is eating a plant, that plant will make chemicals to defend itself, chemicals that make it taste bad to the bugs or might even make the bug sick if the bug eats too much of it.

DARSHANA: Cool defense system.

SANDEN TOTTEN: Yeah, it's pretty sweet. But is it the caterpillar's bites that trigger this defense? Or could just the sound alone be enough to do it?

[MUSIC FADING]

So her team recorded the vibrations caused by caterpillars eating a plant. That's this sound. We altered it so you can hear it. Check it out.

[CATERPILLAR EATING PLANT]

DARSHANA: Nice sound.

SANDEN TOTTEN: Yeah, it's soothing to us, but I don't know. Maybe to a plant, that's like, danger, danger. So Heidi and her team, they played that same sound back to a plant later when the caterpillar wasn't around. And guess what, the plant started defending itself as if a caterpillar was actually there, like the plant was hearing the sound.

HEIDI APPEL: And we looked, and we go, whoa. Can this be true?

SANDEN TOTTEN: So obviously, they tested and retested. They tried other sounds besides caterpillars too, and they found that the plant didn't react to things like wind or being rustled. It only turned on the defenses when it heard the rhythmic chomping of a caterpillar. It could tell the difference. So it's not hearing like we hear, but it's sort of similar.

DARSHANA: So if they can detect this sound, do you think they can tell when we are talking to them or playing music?

SANDEN TOTTEN: Yeah, that's a great question and actually one that I'm very curious about too because I talk to my plants, but I don't want them spilling all my secrets, so I really hope they don't know what's going on. But yeah, a lot of people do talk to their plants, or maybe they play them classical music or heavy metal.

[HEAVY METAL MUSIC]

And here's what I've learned. The plants might feel the pressure from those sound waves, but there's no reason for the plants to react to those noises. It's like wind blowing to them. Some people think maybe your breath might help the plants, like when you're talking to them, because you're exhaling carbon dioxide, but there's not a lot of evidence that it really makes that much of a difference because there's plenty of carbon dioxide in the air anyway. But hey, if it makes you happy to talk to your plants, then feel free to talk, talk, talk away.

MOLLY BLOOM: So the research with the caterpillar sound, were other scientists able to find the same results?

SANDEN TOTTEN: Yeah. Unlike the lie detector stuff, this research held up. And it turns out, this is just the tip of the root when it comes to plant senses. In fact, plant roots are also really good at sensing things. Scientists found that roots underground can tell if something is blocking their path, and they'll grow around it rather than bump into it. The roots can also find water or pockets of nutrients. They even know the difference between the roots of a plant like them and the roots of a different species.

DARSHANA: That's a lot of action underground.

SANDEN TOTTEN: Yeah. So there's plenty of action happening aboveground too. For instance, scientists discovered that plants send messages to each other through the wind.

DARSHANA: Hold up. Messages through the wind?

SANDEN TOTTEN: Yeah. Get this, when certain plants are under attack by a pest or an animal eating it, they'll release signals into the air. And other plants nearby will get that signal through the wind and start ramping up their own defenses. Simon Gilroy, he's a plant researcher at the University of Madison in Wisconsin. He told me, it just shows you that plants are way tuned in to what's going on around them.

SIMON GILROY: Plants are masters at chemistry. You usually think of plants as just being these slow things that are out there, and they're just on their own, but they are absolutely able to talk to each other, and they do it with chemicals.

MOLLY BLOOM: So when roots are rooting around, finding nutrients, that's done with chemicals?

SANDEN TOTTEN: Yeah. The roots give off chemicals and absorb chemicals underground. And Simon told me, when plants are mounting defenses, that message is also sent throughout the plant using chemicals. We have our five senses and our nerves and muscles to interact with the world. And plants, they have chemicals.

SIMON GILROY: So do they sense the world around them? Absolutely. And do they then take that information and process it and then do really amazing things which are entirely appropriate? Absolutely. The parallels of what they do are really close at the big scale about what we do, but the machinery they have is different.

WOMAN: Whoa! Right on.

MAN: Yeah. Dig it. Plants are like us. They must have feelings.

SANDEN TOTTEN: Random hippie types, you're still here?

MAN: Yeah. We wanted to hear the rest of this primo story.

WOMAN: For sure.

SANDEN TOTTEN: Well, I think you're getting a little carried away.

MAN: Yeah, we tend to do that.

WOMAN: For sure.

SANDEN TOTTEN: I mean, we are learning that plants are more aware of the world than we previously thought. But feelings? I don't know, that's a big jump. I spoke to this one plant researcher from UC Santa Cruz named Lincoln Taiz. And he told me that for us animals, we had to evolve our senses and nerves and eventually big brains to create the feelings we have.

LINCOLN TAIZ: Plants didn't even get to the first step of that process, which is to evolve muscles and a nervous system. They didn't take that route.

SANDEN TOTTEN: Instead, plants double down on being sun collectors. They evolved around a strategy of growing and growing and growing, which helps them absorb more sunlight and nutrients. We evolved to move around and seek out food and water and shelter. And feelings are really important to help us avoid danger and seek good things. Lincoln says, for plants, that's just not necessary.

LINCOLN TAIZ: And in fact, it would be a disadvantage, especially if you think of a forest fire. The plant cannot escape a forest fire. If the plant actually felt pain and had feelings, it would be horrible because here they would be trapped by their root systems, unable to move. They have no muscles to move. It would be unbearable for a plant. So it would be a terrible disadvantage for a plant to have feelings the way animals do.

[GENTLE MUSIC]

SANDEN TOTTEN: So as you can see, Darshana and Molly and random hippie types, asking if plants have feelings opens up a lot of other questions. But with science, big claims need big proof to back them up. And right now, there just isn't enough proof of plant feelings for most scientists. But that doesn't mean plants aren't doing amazingly complex things because they totally are. It's just very different from how we do things.

MAN: Out of sight.

WOMAN: Far out. That is so deep, compadre.

SANDEN TOTTEN: Right? So plants don't seem to feel like we do, but they may have their own way of doing things. And people are debating right now over whether or not we should call that intelligence or instinct or something else. So there's plenty of research left to do in this field.

MAN: Wow. Mondo bizarro, man.

WOMAN: Yeah. Let's go meditate on this in the woods. Peace, everyone.

MAN: Peace, man.

DARSHANA: Well, thanks for answering my question, Sanden.

MOLLY BLOOM: Yeah, and for all those epic plant facts.

SANDEN TOTTEN: No problem. And actually, I think I'm going to go check out the woods with the hippies. That sounds kind of fun. Peace.

MOLLY BLOOM: Peace, Sanden.

DARSHANA: Have fun.

MOLLY BLOOM: So, Darshana, do you feel like you understand your plants better now than you did before?

DARSHANA: I do. I'm most-- I'm really surprised about the part that plants can hear caterpillars, and they have defense mechanisms, and the roots, everything.

MOLLY BLOOM: Yeah, it's really cool. Yeah, plants, they seem very quiet. They're just sitting there, but there is a lot going on that we don't notice.

COMPUTER: Brains, Brains, Brains On.

MOLLY BLOOM: So, Darshana, are you ready to try that mystery sound one more time?

DARSHANA: Yeah.

MOLLY BLOOM: And before you hear it this time, I'm going to give you a hint. It's happening outside.

DARSHANA: OK.

MOLLY BLOOM: So here it is.

[MYSTERY SOUND]

All right. What is your guess this time, Darshana?

DARSHANA: It could be wind's rustling or making the trees rustle, move. Or maybe they're raking leaves to make them scraped into a pile, I guess.

MOLLY BLOOM: Excellent guess. Here is the answer.

MAYA: My name is Maya, and I'm from Honolulu, Hawaii. That was the sound of me raking leaves in my front yard. I like raking leaves because it's really fun to jump in the pile when I'm done.

MOLLY BLOOM: Nice work Raking leaves, you got it.

DARSHANA: Thanks. Woo, raking leaves for the win.

SINGERS: Ba, ba, ba, ba, ba, ba, ba, ba, ba, Brains On.

MOLLY BLOOM: All right. We have one more plant-related question to answer.

DARSHANA: This one is from another listener.

[? KAYLIE: ?] Hi. My name is [? Kaylie. ?] I live in Eugene, Oregon. My question is, if a tree decomposes or turns into soil somehow and another tree of the same type is planted in the soil, can the second tree tell?

MOLLY BLOOM: Oh. You know who's been gardening lately? Gungador. I bet he can help.

DARSHANA: Gungador? Isn't he famous for accidentally killing all his plants?

GUNGADOR: Hi! OK. Yeah, but every time plant passes on, I learn something not to do.

[BUZZER]

MOLLY BLOOM: So you've stopped feeding your plants turkey jerky and watering them with laundry detergent?

GUNGADOR: Always learning! Don't worry. I also have science friend to help.

[BEEPS]

KORENA MAFUNE: Hi. I'm Korena Mafune, and I am a scientist that studies forest ecosystems and trees.

GUNGADOR: OK. So for me, this question inspired forest poem.

Old tree dies.

New tree grows.

That's how things in forest go.

Here, Korena. Explain it.

KORENA MAFUNE: So when these trees die, other trees and plants will actually start growing on that dead tree. They call that a nursery log. You can actually walk through a forest and see a dead tree with a bunch of little baby trees and baby plants growing off that tree, and they're taking all of the nutrients that were in that old tree.

It's not like they're stealing it from the tree. It's almost like the tree has passed its time and is now handing off all of its resources to these new plants. And then over many and many of years, that nursery log will decompose and break down and go away.

GUNGADOR: Get this, new trees living on old trees, totally fine, not cannibalism.

KORENA MAFUNE: So yeah, they're not being plant cannibals. There's actually some plants that prefer to grow on nursery logs versus the forest floor soil because it's kind of like this giant sponge for nutrients.

[BRIGHT MUSIC]

GUNGADOR: And living on dead plant does not make new plants sad.

KORENA MAFUNE: There is, say, a footprint of that old plant there, but none of it translates to the new plant being upset that it's being planted on an old dead plant.

GUNGADOR: Amazing! OK. Also, plants can just live on other plants when no plant is dead.

KORENA MAFUNE: Even if a tree is alive, there's other plants that can grow on the trees, and that's not bad for the tree either. Those plants are called epiphytes. Epiphytes mean plants that grow on other plants. You can see ferns growing on trees or even a small plant growing on a mossy patch on a live tree.

GUNGADOR: Ah! Plants so amazing even if they don't know it the way we know things.

KORENA MAFUNE: Plants have been here much longer than us. They do have some form of adapting and evolving and knowing what's the right place to do the right things.

GUNGADOR: So true. OK, there you go. Gungi out!

[BEEPING]

[THEME MUSIC]

MOLLY BLOOM: We've learned a lot about plants by testing and retesting our ideas.

DARSHANA: We've discovered that plants can respond to sounds and share signals with each other.

MOLLY BLOOM: They are aware of the world around them, but as far as we can tell, there's no evidence of plants having feelings like us.

DARSHANA: Some plants also grow well in areas where older plants died.

MOLLY BLOOM: And plants can even grow on other plants. That's it for this episode of Brains On.

DARSHANA: Brains On is produced by Sanden Totten, Menaka Wilhelm, Molly Bloom, and Marc Sanchez.

MOLLY BLOOM: We had special help today from Natalie Walters, Marc Zdechlik, Nancy Yang, Denzel [? Baylin, ?] Britta Greene, Paul Tosto, John Miller, and Jonathan Shiflett. Big thanks to Harsh Bass, Lincoln Taiz, Simon Gilroy, and Heidi Appel.

DARSHANA: Now, before we go, it's time for a Moment of Um.

[CHORUS OF UMS]

Why do bats sleep upside down?

DEEANN REEDER: So why do bats sleep upside down? That's a great question. There's so many things about bats that are really, really cool. Hello. This is DeeAnn Reeder. I'm a professor of biology at Bucknell University, and I study bats.

They're the only mammals that can really fly. And so their hands have become wings, and their fingers have gotten really long, and their legs have turned backwards. And there's all kinds of interesting different ways in which their bodies have adapted to be able to fly, but it means that they're really not very good at standing up.

And so bats tend to roost or hang upside down almost all of the time. And they sleep upside down too. Their feet are like little hooks, and they just grab onto a branch or a piece of bark. And then they can just hang there, and it doesn't take any energy at all.

When they're ready to fly, they just let go. Bats aren't like helicopters. They can't just take off straight up into the air. They have to drop down first in order to fly. So it's really kind of about aerodynamics.

If they were like us, the blood would rush to their brain, and they wouldn't feel well at all. But instead, they have little one-way valves in all of their blood vessels that keep the blood from flowing to their head. Otherwise, their strategy wouldn't work at all.

[CHORUS OF UMS]

MOLLY BLOOM: I'm right side up and ready to read this list of names. It's the Brains Honor Roll. These are the amazing listeners who send us their questions, ideas, mystery sounds, drawings, and high fives.

[LISTING HONOR ROLL]

[THEME MUSIC] Brains Honor Roll

High five

MOLLY BLOOM: We'll be back soon with more answers to your questions.

DARSHANA: Thanks for listening.