Week of wonder: How animals perceive the world

This is Part II of On Point's Week of Wonder.

While you read these words, countless treehopper insects on a branch somewhere in the Panamanian rainforest are listening to one another.

They can’t hear us, and — normally — we can’t hear them.

We both inhabit the same physical world, but our sensory worlds could not be more different.

As Marcel Proust put it:

The only true voyage would be not to visit strange lands, but to possess other eyes. To see the hundred universes that each of them sees.

Today, On Point: That is the voyage science writer Ed Yong hopes to take us on in his new book, An Immense World.

Ed Yong, staff science writer at The Atlantic, where he won the 2021 Pulitzer in explanatory reporting for his work on the COVID-19 pandemic. Author of An Immense World: How Animal Senses Reveal the Hidden Realms Around Us. (@edyong209)

Professor Rex Cocroft, professor of biology at the University of Missouri.

New York Times: "How Animals See Themselves" — "Spectacle floods into my eyes whenever I watch a wildlife documentary. A vortex of small fish is gradually picked off by waves of oceanic predators. Snakes chase after marine iguanas. Giraffes clash at sunset."

Part I

MEGHNA CHAKRABARTI: This is On Point. I'm Meghna Chakrabarti. Ed Yong is our guest today. For the past two years, he's been one of the most prolific and relied upon journalists reporting on Covid. That body of work at The Atlantic magazine won Ed two of journalism's highest prizes: the Pulitzer Prize and the George Polk Award.

He's also been a frequent guest on this program to help us better understand this first-in-a-century pandemic. But that is not why Ed is back with us today. The Covid pandemic was a massive disruption to everything in the world, yes. And to a project that Ed was working on before the beginning of 2020. He had been exploring something utterly, utterly different.

And Ed's with us now to talk about it. So Ed, welcome back to the show. It is so good to have you back here again. First of all, tell me what was that passion project that you had immersed yourself in before Covid changed the world?

ED YONG: Hi, Meghna. Really good to be back and talking to you again. So the project I was working on was a book called An Immense World, which came out last week. And it's about the sensory worlds of other animals. The incredible ways in which the creatures that we share this planet with perceive the world around us.

And at the core of the book is this idea that each species perceives the world in radically different ways. I could be in this room with an elephant, a songbird, a turtle, a rattlesnake. And first you might wonder why I'm in that space with all these animals, how did that happen? But also you would understand that we would all be sharing the same physical space, but we would be experiencing that space in radically different ways.

CHAKRABARTI: Mm.

YONG: And that's what the book is about. It's about going on this voyage through the senses of other creatures.

CHAKRABARTI: So you do present a thought exercise in more detail about what experiencing the world through those different sensory windows would be like, and I'd like to go through that thought exercise in a moment.

YONG: Yeah.

CHAKRABARTI: But first, why spend so long writing about or learning about the way different creatures sense the world? What is it about that that so captured you?

YONG: I think there's two things. I think first we get to understand the incredible things that other animals are doing just by the mere act of existing. And also we learn about aspects of our world that are hidden to us, that we don't necessarily see. So, you know, I am sitting in an Airbnb overlooking a lake right now. I can see a duck sitting on the middle of the lake. That duck, without turning its head, can see the entirety of the sky because it is panoramic vision. It has four kinds of color-sensing cells in its eyes as opposed to just three in mine, which means that it has an entire dimension of colors that it can see and that are invisible to me.

I can see songbirds flitting through the trees. They can likely hear qualities in their own songs that I can't hear because their hearing operates on a faster timescale. If they're migratory, they'll likely be able to feel the magnetic fields of the earth. They'll know which way to fly, even if they were blindfolded or even if it was on a dark, cloudy night.

So by learning more about their senses, I learn about how incredible these fairly common and everyday creatures are. But I also understand that the world around me, this, you know, this view that's already spectacular on its own, is full of information and hidden secrets that I don't have access to and can only understand by thinking about these other animals.

CHAKRABARTI: Did going through this research and learning all about the different ways animals sense the world — did it leave you with the same feeling that I had when I read your book, which was, "Wow, how unsophisticated and rudimentary are the ways that human beings experience the world?" (LAUGHS)

YONG: (LAUGHS) Yes. Yes. I mean, in a way. I think the book is a very humbling — so it was a very humbling experience to write. I hope it feels that way to read, too. I think a lot of the ways in which people have thought about their place in the natural world has been one of like lordship and dominion for many centuries. I think understanding these sensory worlds, you know, knocks us down a peg or two. It tells us that our experience is just one of many experiences.

You know, I don't necessarily think it's impoverished. There are many things that we don't get, like all this, all the stuff I was talking about earlier. But, you know, our eyesight is incredibly sharp. Our fingers are very sensitive, and I think that's just true for every species. Everything is amazing at some things and weak in others. And I think in some ways this area of sensory biology is a great leveler. It shows us that we are just another animal with another way of seeing, of experiencing the world — rich in some aspects and limited in others.

CHAKRABARTI: So could you take us through that thought exercise about how, even in an identical environment, different animals — including homo sapien — are really experiencing entirely different worlds? It was quite captivating how you describe that.

YONG: Sure. So I imagined like a large room, like let's say a school gym. And in it, there is a human. There's also an elephant, a rattlesnake, a robin, a spider, a bumblebee, a dog, a mouse, a bat. All of these creatures are sharing the same physical environment, but let's think about how they would experience it.

You know, the rattlesnake would be able to detect the warmth, the infrared radiation coming off the warm bodied mouse that it's trying to stalk. That's something that most of the other animals in the room would not be able to sense.

The mouse would be able to hear the high-pitched, the high-frequency calls that the bat's making as it's trying to use its sonar to navigate around the room. The elephant wouldn't be able to hear those high frequency sounds, but it would produce low-frequency, infrasonic calls that, say, the mouse or the bat would be unable to hear.

A bee in the room would be able to see ultraviolet colors. If there was a flower in the room, it would look very different to the bee. A sunflower, for example, looks matte yellow to a human, but to a bee it looks like it has a ultraviolet bullseye in the middle, which draws the insect's attention. The robin would be able to see that bullseye as well. The snake and the elephant probably wouldn't be able to.

The dog in the room wouldn't even be able to see some of the red colors that we'd be able to see. Its palette, its visual palette will be restricted to yellow to blue. But it would have access to all these odors that move through the room that, say, the human or the bee wouldn't be able to smell, but the elephant probably can.

So there — the whole point of this exercise is to make us understand that for every creature, including the human, our — what we're getting from the world feels to us to be total, right?

CHAKRABARTI: Yes.

YONG: Like, our subjective experience of the world feels complete. But that is an illusion. It's just a thin sliver of the fullness of reality. And to get the rest of it, firstly, you need some knowledge of what the animals are doing, but you also need to do this imaginative exercise, which is why I start the book by getting people to imagine this gym full of animals.

CHAKRABARTI: Yeah.

YONG: You sort of need to flex your mind to really come to terms with what these strange sensory experiences are like.

CHAKRABARTI: And then, so as you've mentioned, one of those animals of in the thought exercise is a dog. Now you got yourself a pandemic dog, right? (LAUGHS)

YONG: (LAUGHS) I did.

CHAKRABARTI: Typo the dog. What did — tell me more. I mean, because it's one of the most familiar animals to people. Tell me more about, you know, a typical domesticated, domestic dog and how they really are seeing the world through their noses.

YONG: Yeah, absolutely. You know, when when we go on walks, which we do at least three times a day, Typo sniffs his way around our neighborhood. He does so enthusiastically and intently. And it's sort of wondrous to me because I'm walking them the same streets every single day. And to my eyes, those streets are largely unchanged. You might — they might change over the course of a season, but they feel just a little bit boring and mundane. But to Typo's nose, they change every day possibly, you know, on the hour. They're constantly in flux. And he can sense that.

With his nose, he can sense, for example, patches of scent that other dogs have left behind. He can sense things that I don't know what he's sensing. And every walk, there's at least several moments where we will be walk — he'll be trotting along happily, and he will just grind to a halt and start very enthusiastically exploring with his nose some patch of sidewalk that looks completely nondescript to my eyes.

And so through watching him, I understand that the world around me is changing in these profound ways that I don't have access to. I think of him sniffing like patches of pee and like bits of, you know, clearly like bits that other dogs have scent-marked as a bit like me checking my social media feed. It's a way of him catching up on what all the animals around the neighborhood that he's familiar with have been up to recently.

He gets information about where they've been, perhaps some stuff about their health or, you know, what they've been eating. Like his nose can get all of that. And so for him this, what feels to me like just a walk is a little bit of an adventure. You know, it's a social — it's a social event. It's an act of exploration.

CHAKRABARTI: Yeah, a little bit of an adventure. Maybe a grand adventure every single time.

YONG: Yeah.

CHAKRABARTI: We have about a minute and a half before our first break, Ed. I wanted to just quickly hear a little bit about another sense that is completely different in an animal that most of us probably don't think about at all: A mantis shrimp. And the way they see the world. Because they have a lot of — many more cones in their eyes than human beings. So what do they see?

YONG: (LAUGHS) It's really hard to answer this question, let alone in one and a half minutes, but I will do my best.

CHAKRABARTI: (LAUGHS)

YONG: So we have those three kinds of cones in our eyes. They give us access to a certain like, visual rainbow. Birds have four, so they get more colors. Mantis shrimp have 12. So do they have even more colors? Do they have this rich kaleidoscope? Actually, no. It seems like they don't. It seems like they are seeing colors in a completely different way than any other creature.

And, you know, it's not that they have this like, massive rainbow in their eyes. It might be that they're doing something much simpler. And they see the world the way a satellite sees it. The closest analogy we have is to, you know, actually our technology rather than the eyes of another creature. And I think that just shows like how varied and weird and hard to predict the eyes of other animals can be.

CHAKRABARTI: Well, Ed Yong is our guest today. He's author of the new book, An Immense World: How Animal Senses Reveal the Hidden Realms Around Us. We'll talk a lot more about other fascinating species and really the deeper question that Ed is asking us to engage with when thinking about the different ways that animals experience the world. We'll have that when we come back.

Part II

CHAKRABARTI: Ed Yong is with us today. He's the Pulitzer Prize-winning staff writer at The Atlantic. More importantly, he's author of a terrific new book. It's called An Immense World: How Animal Senses Reveal the Hidden Realms Around Us.

Now, Ed, in the book you, early on, ask us — we as human readers — to engage with an important question. And it comes from philosopher Thomas Nagel back in 1979. He asked, "What is it like to be a bat?" So tell us, first of all, why did Nagel even ask that question?

YONG: I think because it's always fascinating to think about being inside the body of another creature, right? It's — this has been a trope of fantasy and mythology and science fiction since time immemorial.

But Nagel's point of view was that just like trying to — that this act of trying to imagine life as another animal is fraught with an inherent difficulty. You know, for example, if you were a bat, you could imagine yourself with like a leathery membrane wing on your arm. You might imagine yourself moving at high speed through the air. But that doesn't even remotely begin to capture the existence of a bat, which senses the world largely through echolocation by making high-pitch calls and listening for the echoes of those calls and using those echoes to map its surroundings.

That's such an an unusual sense to the vast majority of people that it's difficult to imagine what, how it plays out in the bat's head. You know, you're really trying to use sound as a way of gauging distance. You're doing it literally on the fly, incredibly fast, on often very small targets. How does that actually work? Like, it must be flickering because every call gives you a bit of information. But does it meld those flickers into a smooth view of the world like we do with sight? It's unclear.

CHAKRABARTI: Right, it's unclear. So we actually have some sound of bats echolocating. Now, as you just said, this is not normally something that human beings can hear unaided. But through recording and then slowing down the echolocation sounds and lowering the pitch by some 20 times, it does sound like this.

Now that's how it sounds — again, when modified — but does it make sense to us? Well, in the book, Ed, you note that Nagel concludes that, "Bat sonar, though clearly a form of perception, is not similar in its operation to any sense that we possess. And there is no reason to suppose that it is subjectively like anything we can experience or imagine." So Nagel basically asserts that it will be impossible for us as humans to ever truly know what it is like to be a bat. Do you agree with that?

YONG: I do agree with that. I think there's always going to be a subjective chasm there that it's going to be impossible for us to fully cross.

And, you know, the bat actually is a fantastic example of this. Not just because of echolocation, but because echolocation is somewhat unique in being a sense that it's actually reasonably easy to study. The bat is producing the stimulus that it then actually senses, and by changing the nature of that stimulus, it can throw its attention to different parts of its environment to try and wrest different kinds of detail from that environment.

By recording the bat's calls — as the ones you've just played — you can actually get a reasonable glimpse into the bat's intent. You can get as close as possible to kind of reading the creature's mind, simply by listening to the sounds it's producing, because those are the sounds that it's then using to sense the world.

But even so, there is always this question mark, right? Like, what is that experience like for the bat in the silences between those calls? Like, is its experience of the world shorting out? Like, you know, is that like the equivalent of us doing a long blink? Probably not. I think. But I don't know. And that's why this question is — this business of exploring sensory worlds, I think is so — a little frustrating, but also so rewarding. You know, it demands mental effort. It demands these imaginative leaps.

CHAKRABARTI: But you do — I give you credit for trying though, right? Because you --

YONG: Thank you.

CHAKRABARTI: (LAUGHS) Because you do write about how — you walk step-by-step through what it probably is like to be a bat. You engage in that exercise.

YONG: Right. My goal as a writer here is to take — you know, I said that there is this chasm that we cannot ever fully leap. But my goal is to get people as close to the edge as possible so that they can sort of peer over the other side and think about how they might actually make that final jump.

I think it is possible. And there's something glorious about attempting a task that you know you won't succeed in, but you are going to give it a shot anyway.

CHAKRABARTI: Mm.

YONG: That's what it feels like to me to think about these sensory worlds.

CHAKRABARTI: So what did you conclude about what it might be like to be a bat?

YONG: I think I don't know. Right? (LAUGHS)

CHAKRABARTI: (LAUGHS) Okay.

YONG: But so — but — Okay. This is the third way in which the bat example is instructive. There are actually humans who can echolocate.

CHAKRABARTI: Mm-hmm.

YONG: And I met one of them in the book. You know, I met a blind man named Daniel Kish. He's one of many people, many blind people, who can do something similar to what bats can do. He makes clicking noises with his tongue and he uses that to sense his environment. And he does that very well.

Now, Daniel has something a bat doesn't which is language. So he can describe what he's sensing, and surely that's enough to bridge that final chasm. But it turns out, it isn't. Because he's still trying to describe sensory experiences that he, as a blind person, you know, doesn't share with me, a sighted person. We're both using the same words, but do we know we're describing the same kinds of experiences? Well, not really. And so even with the power of language on our side, this is a difficult task.

And yet, how rewarding was it, you know, for me to go and meet him, to understand the way he perceives the world, or to try and do that. I think doing that expands my conception of what it means, in this case, to be human. And then, in the wider case, you know, what it means to be a species on this planet.

CHAKRABARTI: We're talking with Ed Yong today. His new book is An Immense World: How Animal Senses Reveal the Hidden Realms Around Us.

Now, Ed, you know, I actually, I find myself having walked into maybe an expected trap of my own making in that so far I've focused --

YONG: (LAUGHS)

CHAKRABARTI: I've focused on the senses that are most familiar to me as a human, right? We talked about smell and sight. But you, in the book, break down senses into many more categories than just the typical five that we as humans have.

You identify — what? — 13 of them, including : heat, pain, contact flow, vibration. We talked about echoes for a moment. Electric fields. Magnetic fields. Give us an example of an animal that you found particularly fascinating that exemplifies one of these other senses beyond what we as humans have.

YONG: Okay. Let's do a few. So, sea turtles. Everyone loves turtles. They can sense the magnetic field of the earth. And they use that to guide their epic migrations. So a turtle hatchling diving into the ocean for the very first time off the coast of Florida will do a decade-long lap of the Atlantic, moving clockwise. As it moves, it will encounter different magnetic signatures as the earth's feel changes over the planet's surface. The turtle can sense those signatures and work out exactly where it is on its journey and where it needs to go.

If you take it into a lab and expose it to the magnetic signature of, say, Portugal, it knows to head south. And it does this without ever once having been in the water and without having made that journey before. And that to me is truly incredible. It's like the animal has a map of the planet in magnetism and a compass in its head that allows it to use that map.

CHAKRABARTI: Do we understand the biological mechanisms in the animal that allows this to happen?

YONG: We very much do not. And this is a — magneto reception is a sense that not only has the problems we've already described, but has the much bigger problem that we don't even really know how it works. There are definitely some hypotheses. I talk about them in the book, but we don't really know how it works.

We don't even know what the sense organ is. You know, with vision, obviously it's my eyes. With hearing, my ears. With smell, my nose. What is the magnetic sensor in a turtle or a bird? We really don't know. And partly that's because the magnetic field — unlike, say, light or sound — penetrates through tissue really well. So the thing that detects it doesn't need to be on the surface. It doesn't need to be in an eye or an ear. It can be anywhere in the body. It could be in my toe. It could be in my butt. It could be spread out across my entire body and I might not know it if I was a turtle. So it's a very difficult sense to study, let alone to understand and to imagine.

CHAKRABARTI: Well, let's move over to the insect world for a moment and listen to this:

CHAKRABARTI: So that is a recording of the mating songs of leafhoppers. And it comes to us from one of the many wonderful scientists that you profile and encounter in your book, Ed.

And that scientist is Rex Cocroft. He's professor of biology at the University of Missouri. And he records things like what you're hearing now: the sounds of insects on plants, particularly the sound of a family of insects called treehoppers. Professor Cocroft has been studying them for nearly 30 years and recently had a species named after him, Cladonota rex. And he joins us now.

Professor Cocroft, welcome to On Point.

REX COCROFT: Thank you. It's a pleasure.

CHAKRABARTI: Tell us a little bit about what we're hearing.

COCROFT: Well, we're hearing the sounds of these little insects that spend their lives on plants. They feed on plant sap. And they're very small. They're not very good at producing sounds that would radiate in the air. But plants are really exquisite structures for transmitting vibrations. Anything that really touches the plant will create a vibration, a wave that spreads through the plant.

And so they have evolved ways to introduce or inject vibrations into those plants. And then the vibrations just naturally and very quickly travel throughout part or most of the plant. And then other insects have these arrays of exquisite vibration detectors in their legs that they use to pick them up.

CHAKRABARTI: I see. So what do treehoppers look like, for those of us who haven't seen this family of insect before?

COCROFT: Well, this whole group of insects in German are called small cicadas. And essentially their body looks exactly like a miniature cicada. But the interesting thing about treehoppers is that part of the structure on their back has become very exaggerated for reasons that nobody really understands. But it forms kind of strange shapes that sometimes look like the Starship Enterprise coming out of their back.

CHAKRABARTI: Huh. So let's listen to another little example of sound, Professor Cocroft, that you so kindly gave to us. Mainly, this is a demonstration of how there are sound in places where we as humans think are usually totally silent.

CHAKRABARTI: Now, that was — What was that?

COCROFT: So that is the soundscape of a single blade of grass, recorded not far from my house in Missouri. And that's just one example. I could have given you hundreds of examples, but I picked that one partly because it shows how our world interpenetrates with theirs. And how sound and vibration can be kind of interchanged. Because somebody who is familiar with backyard birds might have noticed that they could hear the sound of a Carolina wren in the background.

And plants are very good absorbers of airborne sound, and so an insect's vibrational world on a leaf includes all of those interesting vibrational signals that they produce. And we heard the songs of leafhoppers. Those were male leafhoppers looking for a mate. But it also includes all the airborne sounds that we hear. And so they are not part of our sensory world, but we are part of their sensory world, because they live on these structures that pick up sounds and turn them into vibration.

CHAKRABARTI: Okay, so Professor Cocroft, stand by for just a second because Ed, let me turn back to you. The point that the professor just made is one that you underscore again and again in your book: that we are part of these creatures' worlds, even as we don't sense how the impact of us being part of them are. Can you tell me more about why that's important?

YONG: Yeah, because I think we insinuate our sensory world onto theirs by filling the world with light, with sound, with vibration and sometimes in quite detrimental ways.

Light and noise pollution have been large problems for the animals around us. They've distracted them from the cues that they need to find mates and to communicate. They push them away from habitats that would otherwise be great for them, but are now too bright or too noisy. They might lure them into sensory traps, like turning turtles away from the water or pulling moths literally into flames.

CHAKRABARTI: So Professor Cocroft, have you observed — what kind of impact have you observed of human beings being part of the sensory environment of the treehopper family of insects?

COCROFT: Well, we really are unaware of what a commotion we make when we simply brush past a plant. If there's a family of treehoppers on that plant, they will be communicating about you for five or 10 minutes after you pass, whereas you're completely unaware of them. And so anything that we do while we're moving around and of course, all of our equipment and vehicles that are producing sound or vibration are also picked up, and now have become part of their sensory world as well.

CHAKRABARTI: Well, let's play another bit of sound recording that you've made in the field, professor. This is, again, the treehoppers. And they're not at all what we maybe typically presume insects are supposed to sound like.

CHAKRABARTI: This sounds almost like a synchronized mooing, professor.

COCROFT: That's a perfect description. And I included this one because it shows how these insects — They live in groups and they can use these signals or these sounds to cooperate with each other. And what you heard was exactly a synchronized set of moos from some individuals that were already in a group, and then immediately afterward some running footsteps of other insects that were searching for that group. And using those synchronized moos to locate the group.

CHAKRABARTI: Hmm!

COCROFT: That was a pretty good imitation!

CHAKRABARTI: (LAUGHS) 

COCROFT: (LAUGHS) 

YONG: (LAUGHS)

CHAKRABARTI: (LAUGHS) I'll add it to my list of accidental skills. I love it! Oh, actually I've got a couple more questions for you, professor, but we do have to take a quick break here. So I'll ask you and Ed to stand by for a moment. Ed Yong is our main guest today. We're talking about his new book, An Immense World: How Animal Senses Reveal the Hidden Realms Around Us.

Part III

CHAKRABARTI: Ed Yong is with us today. He's the Pulitzer Prize-winning science reporter for The Atlantic magazine, and he has a new book out. It's called An Immense World: How Animal Senses Reveal the Hidden Realms Around Us. And in that book, he explores all sorts of different kinds of ways that animals experience the world that we as humans do not necessarily have access to.

And Ed asks us a bigger question about how must we go through the exercise of imagining what it would be like to be these other creatures. In so doing, Ed profiles the work of many researchers, and one of them is Professor Rex Cocroft. He's a professor of biology at the University of Missouri and he studies a family of insects called treehoppers.

And Professor Cocroft is with us as well. He sent us a bunch of sound samples of recordings he's made out in the field. And here's another one:

CHAKRABARTI:  So, Professor Cocroft, this one's a little bit different. It's a caterpillar eating a leaf. What should we discern or glean from that sound?

COCROFT: Well, this actually takes us a little bit beyond Ed's book, wonderful as it is. Because for a long time those of us that studied vibrations traveling through plants didn't really think about the fact that these were traveling through a living organism that is itself exquisitely sensitive to vibration, which plants are. And it was only fairly recently that I and my collaborator, Dr. Heidi Appel, at the University of Toledo, thought about the question of whether some of this information that's traveling through the plant could be useful to the plant.

And where I thought we should start is with those munching sounds of a caterpillar feeding on a leaf. And caterpillars can't avoid making those sounds. They scrape off a little bit of tissue, swallow it without any further chewing. Scrape off another. Scrape off another. And they can't help but producing tons of vibration within the leaf.

So in thinking about signals or cues that animals produce and how this relates to their interactions with other species, we need to think about how their predators might sense them. And so that insect's predators can home in on those vibrations.

But we also need to think about how their prey — in this case, the plant — might also react to it. And what we found is that plants actually react to that munching sound by producing more chemical defenses that protect them against caterpillars.

CHAKRABARTI: Oh, fascinating. I mean that's just that, within that topic itself, I imagine there's a whole body of research that's waiting to happen.

COCROFT: That's Ed's next book.

CHAKRABARTI: (LAUGHS) Yeah. Well, my final question for you, Professor Cocroft, is you know, I'm quite inspired by what Ed asks us to do as humans throughout his book. And I wonder if you, in your daily work, ever do this — and that is wonder or try to imagine yourself into what it would be like to be, you know, a treehopper? Or  specifically, even, a leafhopper insect? Is that an exercise that you've ever gone through or wondered about?

COCROFT: Absolutely. I think that's actually an essential research skill. Because the first thing that I would encourage a student to do if they're studying one of these creatures, is to go and sit under a bush and just listen. And try to put themselves into the world. And suddenly you will begin to see some aspects of that world from the insect perspective.

Oh, it's a tiny insect in a huge world. And, "Oh, oh, it's windy now." You just suddenly begin to develop questions about what that insect's experience is like. And I'll say that one of the really wonderful things about studying this vibration, this vibrational modality, is that actually with the aid of a little bit of technology — and increasingly cheap technology — we can actually bridge that sensory gap and enter into their world.

And so you might ask, "Well, how are we hearing something that's only traveling through the leaf?" But with a whole variety of different kinds of vibration sensors, we can actually turn that into sound, and experiencing it using one of our own very well-developed senses. And these worlds of sound within plants are so alien to us that they're really kind of an aesthetic delight.

CHAKRABARTI: Huh. Well, Professor Rex Cocroft, a professor of biology at the University of Missouri. Professor Cocroft, it's been an absolute delight to talk with you. Thank you so much.

COCROFT: Very welcome.

CHAKRABARTI: So, Ed, we've got a question that's come in from a listener, and I think a lot of people are probably wondering about it because we keep talking about trying to imagine ourselves into what it's like to be like other creatures.

And Renee Shapiro says, "Nagel's 'What It's Like to Be a Bat' concerned the question of consciousness and subjective experience. So how appropriate is it for us to judge animal consciousness when we cannot have their subjective experience?" What do you think, Ed?

YONG: I think that's a really good question. And you know, I talk a little bit about this towards the end of the book where I ask people to consider the mind and body of an octopus. It's a body of pure flexibility. Its arms have suckers that can taste, touch and lightly fuses those senses into a single sense. Meanwhile, you know, the head obviously does vision and pretty well. The head and the arms have their own nervous systems that can work, to a degree, independently. So the arms can function on their own with some control over the head.

But this is just an entirely weird setup. It's not just that the animal's sensors are totally different, but it's the way those sensors are packaged into a full creature. It depends on the animal's body. The way its nervous system is arrayed. And so how does one think about that kind of consciousness? How do you imagine what it is like to be an octopus?

It's incredibly hard, not only because we don't share the senses, but because we don't have the body of an octopus. To really understand that this idea of consciousness, you can't just like imagine yourself like putting your mind into another animal's body because it just wouldn't work. And that fantasy idea is fantasy. You need to understand everything about that creature. Its senses, its body, its evolutionary history, how it behaves now. And that's hard, but I think still a worthy task.

I mean, look at, listen to all, think about all those samples that Rex played. You know, what we learned from that is that the plants all around us are thrumming with the vibrational songs of insects that we can't hear. Like, how much richer than does the world feel? Like a garden now feels completely different to me with that knowledge than it did if I was just sitting there thinking, "Oh, it's all very quiet." You know, I think all of this enriches our world. And rewards the kind of hard contemplation that that this field of study entails.

CHAKRABARTI: I completely agree. The feeling I'm left with is one of inspired humility. You used the word humbling earlier.

YONG: Mm.

CHAKRABARTI: You know, but as Professor Cocroft was describing how just walking through, say, a grassy field produces — as a human walking through a grassy field — it produces essentially, a vibrational cacophony, an additional vibrational cacophony that both the plants are hearing and the insects as well. I felt a sense of guilt there for a moment. Because, you know, we're just, we're adding to it just existing as humans.

But then I thought maybe I shouldn't feel guilty because, you know, a bear walking through the same field is creating, you know, a similar vibrational cacophony. And the bear's just being a bear. So we can't, you know, assign any responsibility to the bear for adding to the vibrational sounds that other creatures are experiencing. But the difference between the bear and us as humans is, as your book emphasizes, Ed, is that we have the capacity to imagine ourselves — or try to imagine ourselves, right? — into the experiences of other creatures.

YONG: Yeah.

CHAKRABARTI: And it's a critical difference. And the word imagination comes up over and over again. So does that imagination — or the capacity for that imagination — then also confer upon us an obligation, Ed?

YONG: I think it does, as do a few other things. You know, I absolutely agree with your analogy with the bear. I think one of the differences here is that we have changed the world at a profound rate far and above what other species do.

You know, we have crowded out — so there have been really interesting experiments showing that even the sound of a human voice can push other animals like mountain lions away from their habitat. Because we, in many ways, we act as a super predator. You know, we terrify other animals just by our presence. Now, again, you could argue, well, a bear also does that as a bear's a predator. Yes, but a bear has not, at a global scale, crunched down the ranges of other animals. It's not pushed them out of habitats. It's not squeezed them in this crushing grip. We have. And those actions confer upon us an obligation.

And so does that power of imagination. You know, I think that in that imaginary room I talked about with the elephant and the rattlesnake and the dog and all the rest, the human in that room is likely the only creature who understands what the experiences of those other animals might be. Now, do other animals have knowledge of the sensory world of other creatures? I doubt it. I think that is a human thing, and I think that gives us — that's a gift. It's a profound gift that also confers a responsibility of custodianship.

CHAKRABARTI: And just because though we can't necessarily cross that gap between the world as we experience it through our senses and the subjective experience that other creatures have through their senses, just because we can't necessarily fully make that journey doesn't mean we shouldn't try.

YONG: Yes.

CHAKRABARTI: And you've — about the impact that human beings have had, you do spend an important amount of the book focusing on this. For example, you went into the field with the National Park Service's Natural Sounds and Night Skies Division, and they record soundscapes of our national parks in this country.

And sometimes what they come back is — well, mostly what they come back is — absolutely gorgeous soundscape but sometimes they find things like this.

So that's from Lawn Lake in Rocky Mountain National Park. And of course you hear the birds there and what sounds maybe like wind is actually aircraft in the sky above. So can you talk more about that, Ed?

YONG: Yeah. I mentioned earlier that this problem of noise pollution — that humans have flooded the natural world with noise of our own making in ways that are harming animals either by drowning out their own communications, forcing them out of territories where they can no longer be because it's too noisy, or, you know, sometimes directly physically harming them as in the case for many whales in the use of marine sonar.

Our flooding of the world with noise is not something that we necessarily think of as a pollutant. You know, we don't think of noise pollution in the same way as we do like, chemicals flooding out of a smokestack, for example. But it can be just as harmful to the creatures around us. And in very sad ways. I've described sensory pollution as the pollution of disconnection. It severs our relationship from the natural real world. It disrupts the ties that bind other creatures together.

Whales, big whales, used to be able to hear each other over the distances of almost an entire ocean. And because of how much noise there is now in the ocean because of ships and and so on, a whale's world is much smaller than it used to be. And because these animals are so long-lived, there will be whales alive today that once knew what it was like to hear an ocean full of whale song and now can't. And that's what we're living through.

You know, there's a reason why at the start of the pandemic when people stayed at home and were — just generally, the world was quieter — everyone started saying, "Are you hearing more birds?" That's because with quiet, with silence, we actually get to perceive the natural world that exists all around us that we're usually oblivious to.

CHAKRABARTI: Mm. I still struggle with the fact that no matter how hard we try — and we should try — we're still fundamentally limited in how we can understand the sensory perceptions of other creatures. Because ultimately we have to convert them into a set of senses that we can take in as humans, right?

YONG: Mm-hmm. Yeah. Yeah. I absolutely agree. But here's the thing: We don't actually need to completely cross that sensory — to know the consequences of our actions. I don't need to know what it is like to be a moth to know that a moth is lured to a streetlight in ways that might be fatal for it. I don't need to know the details of how a sea turtle reads the earth's magnetic field to know that a baby sea turtle will sometimes wander up a beach that's brightly lit with fatal results instead of towards the ocean where it needs to go.

The consequences of light and noise pollution are very clear through a lot of careful experimental work. And therefore the obligation on us to reduce those forms of pollution is upon us now. And the fascinating thing about this, I think, is that this is an area where we can actually do a lot of good very quickly for not that much effort.

Light and noise pollution are not like plastics. They're not like pesticides in the environment that are going to persist for decades after we turn them off at the source. If you just switch the lights off, if you reduce the speeds of the vehicles, if you just do simple things to reduce the amount of lights and noise in the world, this problem becomes drastically less problematic very very quickly. It's kind of an ecological gimme and it's something that we should — that's something we should take advantage of.

CHAKRABARTI: Mm. Well, Ed, in the last minute that we have I'm curious: Of all the fascinating animals that you studied and tried to understand how they're experiencing the world, was there, or is there a particular sense that if you could have, if you could add to your human view of the world, that you would?

YONG: Oh. You know, they're — it's so hard because they're all my babies. You know, would I love to  have a compass like a turtle? Would I love to be able to sense the electric fields of the world like a shark or a platypus? Absolutely. I think probably my answer to this question varies from one day to the other.

But for today, because I'm away from him right now and I miss him, I'm gonna say, I would love to smell the world like my dog, Typo. I think it would make us a little closer.

CHAKRABARTI: Well, Ed Yong is a staff science writer at The Atlantic. He won the Pulitzer Prize and the George Polk prize for his writing over the past two years about the Covid pandemic. But today we talked with Ed about his wonderful new book. It's called An Immense World: How Animal Senses Reveal the Hidden Realms Around Us.

And Ed, I thank you for this book because now as I walk through the world and see other creatures, I'm going to ask myself, "How are you experiencing this moment?" as well. So, Ed, thank you so much.

YONG: Thanks, Meghna. Always a pleasure. Take care.