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How much brain do you need to be smart? Bees and ants perform marvels as colonies, though each insect has barely any brain. And plants—with no brain at all—exhibit behaviors that, by any definition, count as intelligent. Brace yourself for a mind-bending exploration of plants that learn new behaviors and warn their brainless fellows of danger; vines that compete with each other; molds that solve puzzles; and trees that communicate and cooperate through a ‘wood-wide web’ of microscopic mycological fibers. Perhaps the real question is, are we smart enough to appreciate the vast range of intelligence that surrounds us?

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NATALIE ANGIER:   Good evening and welcome to this wonderful festival. You may not notice it because you’re in New York, but plants actually dominate the earth’s environment. They make up about 80% of Earth’s biomass. And by comparison, all animals, including us, amount to less than half a percent; or as one plant biologist puts it, just traces.

NATALIE ANGIER:   We want to begin with a question. How have plants managed to be so successful when they don’t have any brains? Or do they? Can plants learn, think abstractly, even communicate? To begin, let’s start with a little film about the checkered history of the study of plant intelligence.

NARRATOR: Look, let’s be honest, the idea of intelligent plants seems like a flashback to the ’70s, when many believed that plants enjoyed listening to music and having us talk to them. Those ideas had their roots in the work of this guy, Cleve Baxter.

CLEVE BAXTER:      Welcome to the Baxter School of Lie Detection.

NARRATOR: A former CIA lie detector expert, who claimed he could communicate with plants telepathically.

CLEVE BAXTER:      I have to get a certain distance away from the lab, so that my consciousness won’t affect the results.

NARRATOR: Baxter’s research was popularized in the book, The Secret Life of Plants, published in 1973, which also claimed that plants prefer classical music to rock-and-roll, and that they have emotions.

WOMAN:       The plant attached to the instrument is able to feel the mutilation of its comrade.

MICHAEL POLLAN:            The Secret Life of Plants, it was insane, but very popular. It was a huge bestseller. It turned out to be full of pseudoscience and, I think, gave a bad name to the whole area of inquiry.

NARRATOR: It was a major setback to a field pioneered by Charles Darwin in the late 1800s.

MICHAEL POLLAN:            Darwin was convinced that plants had an intelligence.

NARRATOR: He proposed that this intelligence resided in their root tips. Later, in the early 20th Century, scientist Jagadish Chandra Bose demonstrated that plants were aware of their environment and responded to electrical stimulation. And time-lapse photography offered a new perspective on their behavior.

MICHAEL POLLAN:            Time-lapse is amazing because plants operate in a different scale of time than we do. We’re continually being surprised by what they can do and how sophisticated they are; to send signals to one another, to trade information, and trade goods.

MICHAEL POLLAN:            This is two bean plants, and they’re sensing one another and competing over this pole, and they’re not both going to get it. You’ll see that one of them gives up on that pole and starts looking elsewhere.

MICHAEL POLLAN:            So how are they aware of each other in space? I don’t think we know yet.

NARRATOR: There is growing evidence of plants that communicate, learn new behaviors, compete for resources, and even respond to attack. And it’s not just plants. Fungi appear to share resources and information through a wood-wide web, a microscopic network of tree roots and mushroom fibers. Leading us to wonder if it’s time to expand the definition of intelligence to include organisms with no brains at all?

NATALIE ANGIER:   How many people here talk to their plants? Well, our first participant, I don’t know if she does, but I wouldn’t be surprised because she does amazing work and is willing to go out on the edge. She’s a professor of evolutionary ecology at the University of Sydney in Australia. Her work is raising profound questions about plants and their ability to communicate, learn from experience, and cooperate. Please welcome Monica Gagliano.

NATALIE ANGIER:   Our next guest is a professor of forest ecology at the State University of New York’s College of Environmental Science and Forestry, where he studies the wood-wide web, a phrase I love, a hidden network of underground fungi that connect plants and trees. Please welcome Tom Horton.

NATALIE ANGIER:   Rounding out our first group of guests is a professor at the New Jersey Institute of Technology, where he directs the SWARM lab. He is a biologist who studies collective behaviors in slime molds, army ants, and robots. Please welcome Simon Garnier.

NATALIE ANGIER:   Let me start with you, Monica. You’ve done pioneering work to help establish the field of what’s called plant bio-acoustics. And one of your first experiments involved chili plants. Can you tell us about this, and what you were trying to answer, and what you found?

MONICA GAGLIANO:         Sure. Well, first of all, that was indeed my first experiment with plants, because I used to work with animals. By training, I’m an animal ecologist, working with fishes on the coral reefs. I didn’t really know anything … I still don’t know very much about plants, but they are teaching me, so that’s good.

MONICA GAGLIANO:         When I approached the question of communication in plants, which, of course, in the animal fields is really an easy question to ask, because we ask it all the time, I started from, “Okay, so what do we know, if we know anything about communication in plants?” And there were three main channels. Plants, we knew they use light to tell who is growing next to them and whether it’s a problem or not. They use, of course, chemicals. And touch, basically; if they bump into each other, they know that’s no good. And depending who they’re bumping into, they will change their behavior, too.

MONICA GAGLIANO:         Okay, so what happen if I shut down those possibilities of communicating? Would they still know who is growing next to them? So I used chili’s just because they seemed easy to grow; that was the very deep and meaningful reason. Then I used basil plants as the good companions, and the fennel, which is known in companion planting, for anyone that has grown a garden, fennel can be quite aggressive, and so usually it is not planted in the veggie patch with everyone else.

MONICA GAGLIANO:         I thought, “Okay, fennel is going to be my bad guy and basil is the good guy. And I wonder if the chili knows who is inside the box?” I created these Matryoshka boxes that would lock up the plants into like, “Okay, I can’t see you. I can’t smell you. I can’t touch you. Would I know, as a baby chili, who is there?” And they did. So then, it was like, “Oh no! And now?”

MONICA GAGLIANO:         Then, of course, as often is the case, when you stumble in those places, like, “Oh no! Now?,” I think you know you’re onto something, even if you don’t know what it is. Basically, I was, like, “Okay. So, obviously, they know, and obviously they must use some other way of knowing that is not what we already know about them.” Because of my animal background, I kind of went into, “Oh, maybe, sound?,” because sound in animal ecology is used everywhere we’ve looked. Maybe there are other channels, as well? So the bio-acoustic kind of developed from stumbling into, “I don’t know what’s happening here.” But it’s often the case in science, I would say, right? So, yeah.

NATALIE ANGIER:   So you discovered that they were tuning into the sound of-

MONICA GAGLIANO:         They knew exactly who was growing next to them. Yep.

NATALIE ANGIER:   Then you also discovered that plants not only respond to sound but also make sounds.

MONICA GAGLIANO:         Yeah.

NATALIE ANGIER:   Can you talk a little bit that?

MONICA GAGLIANO:         Yes. I guess that one was the more disturbing part for many of my colleagues. Because, one thing is, like, “Oh, well, okay. They might respond to the sounds surrounding them,” and it kind of makes sense. But the fact that they might produce their own sound, so they have their own voice. Which is different than plants singing or plants making music, just to clarify.

MONICA GAGLIANO:         Yeah. And, actually, this work was done with colleagues in Bristol. And they were also animal ecologists, working with insects, of all things. They were looking at how the antenna of certain insects, including tiny mosquitoes, pick up vibrations and produce their own vibrations. So we use the same technology, which is laser technology, and basically we check plant roots instead of mosquitoes’ antennae. And then, of course, there was the signal. And it was, like, “What are we going to do with this now?”

MONICA GAGLIANO:         And this is the signal. It’s looped because we only had brief times. But, yeah, this is our plant sound like, when it’s producing its own sound. Of course it’s loud, at this stage. The frequency is within our audio range, as well. Which means, potentially, our ears actually could hear this, it’s just that the amplitude, so the volume of that sound, is not very loud. You can imagine, roots are under the ground, so when people ask me, “Oh, so do you think that I could hear it?,” I was, like, “Absolutely. If you’re ready to put your ear on the ground, be super-quiet, and wait.” And most people are, “Ah! Okay. I believe you.”

NATALIE ANGIER:   I’ll take your word for it! Well, I imagine that your colleagues were skeptical about this, to say the least?

MONICA GAGLIANO:         Very kind!

NATALIE ANGIER:   So is the field of plant bio-acoustics, now, you think, considered wholly legitimate?

MONICA GAGLIANO:         What are you laughing at?

SIMON GARNIER:    I’m laughing at the question, not at you.

MONICA GAGLIANO:         Okay. Good.

MONICA GAGLIANO:         Well, like is often the case in science in particular, but I think in many spaces of human endeavor, at the beginning it’s always tiny steps, and hard, and that kind of thing. And then suddenly one person, and then another group, and then … they start building. And as knowledge builds, we get more comfortable about the ideas, and then it’s kind of, like, “Yeah. It’s a no-brainer. We knew that.”

SIMON GARNIER:    Did you prepare that one?

MONICA GAGLIANO:         Eh?

SIMON GARNIER:    Did you prepare that one?

MONICA GAGLIANO:         Yeah. I did!

SIMON GARNIER:    Okay.

MONICA GAGLIANO:         Philosophers have told us this before. It’s the history of science, and maybe not just science. And so, I guess we are at a point when I’m starting to see … and even sent papers to review on this. I know! So the fact that they even consider me a legible reviewer is amazing. So the fact that there are these works coming through, it’s a great sign.

MONICA GAGLIANO:         And I remember earlier on, when, sometimes, doing an interview, and someone was, like, “So what you hope … out of this work?” And of course, often, they think, like, “Oh, I become famous,” and I was, like, “I hope it becomes totally redundant.” And it means that it’s so obvious, and it’s so acceptable- accepted, that we’re not even going to talk about this. Because it’s just like a given. It’s, like, “Ah, of course. Ah, yeah, we all know that plants make noise, you know?” So that, still, is my best wish to that science.

NATALIE ANGIER:   So, Simon, you work in something else that maybe people are skeptical about, that is intelligence of slime molds.

MONICA GAGLIANO:         Yeah! Now who’s laughing?

SIMON GARNIER:    All right!

NATALIE ANGIER:   But tell us what a slime mold is? It’s not a plant or an animal. Is it a fungus? What is a slime mold?

SIMON GARNIER:    It’s not a plant. It’s not an animal. It’s not a fungus. It’s not clear where it fits in the tree of life. It’s little scientific name is Myxomycetes, I guess that’s the way you would pronounce it. It’s a very weird organism, there’s no question about this. It’s actually an uni-cellular organism that can be pretty big. All the yellow mass you see is one single cell, here. And that can be several … You can grow it on several square feet if you have enough time and food.

NATALIE ANGIER:   And that’s a single cell?

SIMON GARNIER:    It’s a single cell. But unlike the cells you have in your body that all have a single nucleus, these can have millions and millions of nuclei inside; it’s called a syncytium. Yeah I mean, a little bit like you, right there, I’m an animal behavior specialist originally. The reason I study slime molds is because I hired a guy, a few years ago, to work on ants, and then he came and said, “I want to work on slime mold instead.” And I was, like, “Fine. What do you want to do with it?” And he was, like, “Well, I want to … I, then, play the casino.” And I was, like, “All right!”

NATALIE ANGIER:   Play the casino?

SIMON GARNIER:    The casino.

NATALIE ANGIER:   Uh-huh.

SIMON GARNIER:    So we did an experiment where we had slime mold play the casino. And then the results were, the slime mold was actually pretty good at it!

NATALIE ANGIER:   Oh yeah?

SIMON GARNIER:    It wins against the casino. So slime mold is capable of solving this problem that seems to be a typical problem that we normally ask to an organism with brains. This casino experiment is called the Multi-Arm Bandit Problem. It’s something that is studied in pigeons, in humans, in all sorts of brained animal. And then we showed that it actually can be solved by organisms that don’t have brains, don’t even have neurons. And that’s how we started.

SIMON GARNIER:    And then, this summer, we are very close to actually showing what are the molecular mechanisms that are allowing them to make these decisions. If you allow me to talk about this?

NATALIE ANGIER:   How do they do this? What are they doing then?

SIMON GARNIER:    So they actually use their muscles for that, which is kind of contradictory.

NATALIE ANGIER:   Their muscles?

SIMON GARNIER:    Yeah, so the slime mold … If you have the video? If we can show the video again, you might see that you have this pulsation. This is actually sped-up, but this pulsation happens about every minute, minute and a half, in the slime mold. And then it’s actually the membrane of the slime mold contracting and expanding, and choosing actin, myosin, which is same type of proteins that are used by your muscles to contract; that’s why I call them muscles.

NATALIE ANGIER:   Okay.

SIMON GARNIER:    And that pulsation is essentially what helps the slime mold redistribute its biomass throughout its entire body. Now, what we see to be happening is when the slime mold hits something that tastes good, it actually relaxes there. And just by sheer physics, right, everywhere else is pulsing, and so there is a influx of matter that is going toward that location where that started relaxing. So it makes decision by finding something nice and then relaxing there.

NATALIE ANGIER:   Mm. And it can also solve mazes, too?

SIMON GARNIER:    Yes. It’s a very famous experiment. We actually won the Ignoble Prize back in 2001.

NATALIE ANGIER:   Ignoble?

SIMON GARNIER:    If you don’t know, the Ignoble Prize is a prize for science that, first, make you laugh, and then make you think.

NATALIE ANGIER:   Ah!

SIMON GARNIER:    It’s not my prize. I didn’t invent that. But, yeah, so a group of Japanese researchers, they actually won for their research on slime mold twice, the Ignoble Prize. First, with these experiments where they showed that if you put the slime mold on a maze, it’s capable of actually finding the shortest path between the entrance and the exit of the maze. Which is something that, if you have a three or four year at home, they’re not capable of doing this yet. They will at some point. If they don’t, then you have a problem.

SIMON GARNIER:    And then the second experiments that they done, which I think we have a video of that, with the map of U.S. Yeah, so that’s sort of re-creation of that experiment. But this team worked on the Tokyo subway network, so they reproduced the Tokyo subway network using pieces of food, pellets of oat flake, which for some reason the slime mold loves. And they showed that the slime mold will create a network connecting all these different pellets. And the property of the network is very, very close to a perfect network that engineers would design to connect different train stations in the Tokyo area. And that won, also, the Ignoble Prize.

SIMON GARNIER:    But these two experiments sort of kick-started this field in biology of the intelligence of slime mold, and how they’re capable of solving this problem. And that was, just, about 15 years ago now.

NATALIE ANGIER:   Do you see this as some kind of intel- … I mean, would you define this as intelligence?

SIMON GARNIER:    I try to not use the word intelligence when I can. I use the word problem-solving, because I can define this as a problem. The problem in this case is … the case of the network, for instance, is balancing things like the cost of building the networks, but also the robustness of the networks to perturbation. And so, that’s a problem, a trade-off that they need to be able to solve.

SIMON GARNIER:    The question of whether that is something that we consider intelligent, it depends on how … I mean, we can backtrack a little bit, but in the story of testing intelligence or measuring intelligence, we have created a battery of tests. And some of these tests are about optimizing this trade-off. And so, the question is, now, either we have to discard all these tests because slime mold passed it, and decide that these tests actually don’t test intelligence, or we have to admit that they are intelligent. But I will not pronounce on it because I don’t want to be reviewed, too.

SIMON GARNIER:    Essentially, it’s a question of, they pass test that we have given to brained animal, and then we have considered this a test of intelligence. I’m guessing.

MONICA GAGLIANO:         Well, and the word itself, just the actual root of the word, basically means “choice between.” So if you choose to go that way instead of this way, and then you choose again, and then you choose again, and you’re directing that choice to resolve a problem, then by that definition you would be intelligent.

MONICA GAGLIANO:         But, again, I agree with you. It’s like problem-solving, decision-making, seems a bit more appropriate. But not just for the slime mold, or the plants, or whatever, but even for us.

SIMON GARNIER:    You define the problem in a way that can be testable.

MONICA GAGLIANO:         Yep.

NATALIE ANGIER:   So, Tom, you’re working on another part of this biological kingdom, looking at the interactions between fungi and trees. What is this wood-wide web, and what is at the root of these networks?

TOM HORTON:        Root of these networks? The roots!

TOM HORTON:        So the wood-wide web, I guess I could think of my own history through this. I was a plant ecologist first, and watching how certain trees could … a seed would land and get established here, but not over there. And find out that there were very different fungal networks underground that would support the tree here, but there’s different group over there. And I was fascinated by that, and I started to dig-in a little bit! Okay, we should just … I should just stop right there!

SIMON GARNIER:    I’ve got to up my game because I’m not very good at it.

TOM HORTON:        What I discovered is that plant ecology has largely worked, in the absence of understanding what’s going on below ground, other than the roots. And so, when we’ve tried to figure out how do nutrients get to plants, we either use a hydroponic system in the absence of the fungi, or we use something like Arabidopsis, the lab rat of plants, that is in a family that doesn’t form mycorrhizal associations.

TOM HORTON:        Well, here, is a single seedling associated with one fungus. If any of you know your fungi, that’s a swillus. You wouldn’t know it because it’s not making a mushroom on top. But that network is very much analogous to the Myxomycetes network, the slime mold. They’re going after resources. You can see nodules with the root tips. They’re getting all their carbon, so their primary resource is carbon, from the plant, that’s the sugar. And then that fan of hyphae are very actively searching for other nutrients, like nitrogen or phosphorus. And so, you see this beauty … And you could plug a little plug of nitrogen in one spot in that little microcosm, and the hyphae will hone-in on that spot. And if you label that phosphorus it shows up in the plants very quickly. The fungi harvest it, and it gets back up into the plants.

TOM HORTON:        I was fascinated by that. I thought, “My gosh! Let’s read more about this.” I looked into botany textbooks I had, there was a paragraph on mycorrhizae. I looked in The Ecology, and probably the word occurred, often spelled right. I was fascinated. And this was back in … Not long ago, for some us, 1990, or so. It started to get into the ecology textbooks-

SIMON GARNIER:    I was still in high school.

TOM HORTON:        Sorry?

SIMON GARNIER:    I was still in high school.

TOM HORTON:        Oh gosh! Listen, son!

TOM HORTON:        And I thought, “What am I going to do for my career, other than I get to study fungi?,” which, I’d already had a fascination with this. I realized that plant ecology needed to go … I could get in there and understand the fungi, and bring mycology into plant ecology.

TOM HORTON:        Jumping ahead. So that was the paper published in that journal by Suzanne Simard, which some of you may have heard. And if you haven’t, you should really look up her work. She was showing with isotopes, that is labeled bits of carbon, that douglas fir was communicating with birch, in mixed stands like you’re seeing here. The birch is in fall colors, the douglas fir’s a conifer, obviously. And that communication is very active out in nature. I am very interested in how that impacts seedling establishment during succession, say, after a fire. But she has been showing that there’s this communication in these forests; they are not static individuals, there’s this larger holistic thing going on below ground that we’ve been walking right over. Ha-ha! Sorry. I’m sorry. I couldn’t resist.

NATALIE ANGIER:   It’s okay! So these fungi are sort of acting like little electrical wires, or pipes, or …?

TOM HORTON:        I see them as highways.

NATALIE ANGIER:   Highways?

TOM HORTON:        And going back to the next slide again, to the next … That one. You can see the highways. Let’s see, I don’t know my highway names here, but it’s a through-way, and then there’s city streets, and then there’s place you could walk. And it just, increasingly, gets finer and finer.

MONICA GAGLIANO:         Oh watch out! Watch out! This-

SIMON GARNIER:    No. No. It’s an honest question. So when you talk about communication, are you talking just, like, exchange of nutrients, or actually signals that modify the behavior of the other partner?

TOM HORTON:        Yes. So I’m talking about sharing, or movement of nutrients.

SIMON GARNIER:    Okay.

TOM HORTON:        In my world, I feel that nitrogen, phosphorus, are highly interactive, are moving throughout the networks. In our arbuscular … And this is going to get a little bit too much in the weeds but I’m going to try. In the arbuscular mycorrhizal fungi, which associate with 70% of the plants that you see out there … so, in a field, they’re all interconnected through these mycelial networks. Doesn’t matter how many there are. This would be a meadow though, not trees … they are all one cell. There are no septa.

SIMON GARNIER:    Oh!

TOM HORTON:        Like your slime molds.

SIMON GARNIER:    Slime mold.

TOM HORTON:        And there are thousands of nuclei. And when they make a spore … I’ve seen videos where the nuclei are moving along as the spore expands and they’re delivering thousands of nuclei into the spore, and sometimes the nucleus goes through the little branch and comes back out and decides not to! There’s a lot we don’t know.

TOM HORTON:        But if I could to the next slide. So this is, remember, one individual of fungus. Here are two species. In the ectomycorrhizal world, where the trees are, at least in North America, the temperate forests, they are not all one cell, and nor do they really interconnect into one continuous stream. They’re all … Well, to put it in a … They’re all in it for themselves, maybe one way to look at this.

TOM HORTON:        You can see that these two hyphae are different species and they are not connected. So they may be off the same tree, the nutrients may be going from the tree into both, but they’re not interconnected, they’re not utilizing each other’s resource base. And the same thing for the fungi: they’re after the phosphorus and the nitrogen, they’re bringing it back to the tree, but they’re not doing it together, they’re not doing it as a single unit.

TOM HORTON:        Did that answer your question?

SIMON GARNIER:    Yes.

TOM HORTON:        Thank you. Because you gave me a great soapbox.

SIMON GARNIER:    My question was about whether that communication affected the behavior of …

TOM HORTON:        Yeah.

SIMON GARNIER:    Of if was just an exchange of-

MONICA GAGLIANO:         … resources.

SIMON GARNIER:    … resources. Maybe, if I pop a plant here, will that modify the behavior of the plant there?

TOM HORTON:        That’s a great question.

SIMON GARNIER:    That’s what I’m trying to get at.

TOM HORTON:        So the one data point I could bring in, from the research I’m aware of, is that if a plant gets chewed on by an insect … And the experiment was elegantly done with all the controls in place … that plant can send signals that will go through the mycelial network, and the next plant will put up its defenses.

MONICA GAGLIANO:         Prepare for battle.

TOM HORTON:        And if you break the hyphal network by cutting them, it doesn’t happen. And it’s not going through the air, that signal, it’s not going through the roots, it’s going through the mycelia. So there is communication.

SIMON GARNIER:    Yeah. That’s really cool.

NATALIE ANGIER:   So it’s kind of using it like infrastructure? It’s really just taking advantage of it?

TOM HORTON:        Yep. And published within the last five, six years, maybe. And there’s more. There have been many more papers on that.

MONICA GAGLIANO:         The chemical communication, both, below and above ground, is crazy. It’s like it’s happening at a rate. And it’s mirrored in the literature, in the scientific literature, how many papers are coming out, and how many different combinations of studies in plants, they’re being looked at in that context specifically. So it’s pretty cool.

TOM HORTON:        But isn’t it fascinating that we have the textbooks that we’re using, from high school, up through to college, up through graduate level books that people are using, and they forget to mention the mycelial networks, the fungi.

SIMON GARNIER:    Are you saying textbooks are behind their time?

TOM HORTON:        They’re a little … Yeah.

SIMON GARNIER:    Maybe it’s time you write the next one?

TOM HORTON:        Well, I have been involved but it doesn’t get fair play, and I’ve stopped being … No! Sorry!

SIMON GARNIER:    Sorry!

TOM HORTON:        Yeah, right!

NATALIE ANGIER:   Do you see this is a kind of symbiosis, or are somewhat, like, mutually exploiting each other in some way?

TOM HORTON:        Oh, that’s great! I love that! So, in my lab, we often throw that question up, and we say, “Is this the mutual … What is a mutualism?” Reciprocal parasitism.

NATALIE ANGIER:   What do you mean by that?

TOM HORTON:        So they’re both … One organism needs the carbon. I mean, the plants don’t need carbon: it’s the number one resource that most of us need, but plants don’t; they fix it. And they make a lot of extra, and they leak it down into the roots in support of microbial community. But they do need nitrogen or phosphorus. And it’s the other way around for all the microbes; they need the nitrogen … Excuse me, they need the carbon, but they can get, with all carbon from the plants, they can go out and explore, and absorb through extra-cellular digestion, the nitrogen and the phosphorus. A lot of enzymatic activity, movement of material through the hyphae, through septa, et cetera.

NATALIE ANGIER:   So it’s not like some guy at a commune, sort of relationship?

TOM HORTON:        Well, if I go back to, when I started my Masters, I was in San Francisco, and I was, like, “Man! This is the ’60s all over again!” Just like that film, only jump back one decade. I was, like, “Wow! This is so cool. I got it.” But then things started to get a little harder during my degrees, and it became a little more competitive, shall we say?

NATALIE ANGIER:   You did some experiments with the mimosa plant that, I guess, was also sending ripples through the field of plant biology, because it did suggest that there was learning and, actually, remembering, for a surprising amount of time. Can you talk about these experiments?

MONICA GAGLIANO:         Well, I should clarify, it wasn’t a suggestion, it was data-driven. So it was demonstrating, which is different. And I’m clarifying this because one of the typical comments that I would get about that study was, “I don’t believe you.” And I’m, like, “Okay. You don’t have to. But can we talk about my data. I mean, are you a philosopher, or are we doing science? Because, I don’t know, if we’re talking about philosophy then, maybe, yeah, you’re right. Depending on what is your vision of learning and memory and whatever, then maybe there is something there to discuss. But if we’re talking just about the science of … And this is experimental science, so here is my experiment, here is my data. Let’s talk about that.”

MONICA GAGLIANO:         And, yeah, there wasn’t much of a willingness to talk about the data. But the experiment was very clear. And it was a mimosa pudica, or the sensitive plant which, of course, as you saw, as well, in the little video at the beginning, it was a plant that used from Darwin to Bose and many others. And, actually, is a plant that, even from the ancient times, has always attracted our attention. Why? Because it moves at our timescale, and so we can actually see it doing something.

MONICA GAGLIANO:         And so, it’s, like, oh yeah. Mimosa does behave. Everyone else is just static and seen as a kind of object in the background. And that actually does have a term, and it’s called plant blindness. And it comes from the education research, which has demonstrated that humans are, kind of, blind to plants. And since … when we are little as well. So, at school, kids find it very difficult to recognize plants, but they are very good at recognizing animals that they would never, ever meet. Like a lion. If you show them a tomato plant, they’d be, like, “I don’t know.”

MONICA GAGLIANO:         But, anyway, that aside. So Mimosa was a choice because it was a good bridging point between … learning and memory is naturally associated with something that animals do. So using a plant, or having a plant as a model for testing this kind of question, that are normally restricted to animals, was … a plant that moves was a good starting place. Right? And the experiment was very simple because of what I did, I started looking at the most basic level of learning. And even within the animal literature, we talk about this kind of learning, which is, the technical term is habituation. And you are doing it right now, because you’re not paying attention to the lights, to the smell, to the temperature, to things … You are, but you kind of, you have already decided that it’s not going to kill you right now. So you can kind of ignore it. But if the alarm was going to go off right now, your body would be ready to respond.

MONICA GAGLIANO:         So the idea of habituation is that you are bombarded by all this information, or signals, and your body is detecting them, and then, kind of, waiting. But this happens mostly unconsciously. Waiting to decide whether this is going to be a problem or not. And if experience tells you, “Look, you can ignore it,” then you ignore it so that you can actually focus, maybe, on the person talking in front of you, or maybe not. Maybe you already, you have just habituated to this too, and, like, who knows? The idea is very simple; you can’t pay attention to everything that is happening around you, all the time, because you wouldn’t last very long. So you cut out, you remove the information that is irrelevant to you right now. But you want to be responsive in case some relevant bit of information arrives, like the alarm.

MONICA GAGLIANO:         So I did the same the experiment, and I used mimosa. And basically the question was the same, it’s like, if I do something that is kind of scary or disturbing, at first, but it’s not deadly. It looks like it could be potentially a problem but, actually, through experience, the plant should realize that, well, nothing really happens. So this plant closes the leaves quite rapidly when it’s disturbed. And so, as you just saw, I created this kind of torture thingy! But no plants were hurt, really, during the conduction of this experiment.

MONICA GAGLIANO:         So basically I would drop the plant, and the base of that structure is foam, so the plant will be dropped from a set height. And of course, the first time that the plant is dropped, the plant close the leaves, because it’s, like, “What was that?” Then you do it again, and then you do it again, and this is exactly what we would do if it was an animal. You repeat, and you repeat several times. And what we call that repeat is a train. And the train for this experiment was, like, 60 drops, consecutively.

MONICA GAGLIANO:         But what happened, as you can see from that cartoon, is that the plants actually after two, three, of those, supposed to be 60 drops, they went, like, “Uh! I got it. I got it. Nothing is happening, and I’m not bothering closing my leaves.” And it makes total sense because of course, open leaves, full photosynthetic capacity, right? When you close your leaves, you might protect from predators, for example, so that you look smaller. Or this plant has got spines, they stick out when the leave are closed. You’re defending. But if there is actually no danger, you’re defending against nothing. But by closing, you are cutting away your opportunity to feed on light. And for this plant, when the leaves are closed it loses 40% of photosynthetic capacity. That’s a lot, especially if there’s no reason.

MONICA GAGLIANO:         And so, in my experiment, actually, I had plants that were in an environment where there was lots of light, so making a mistake is not that critical. You can make an extra mistake and it’s okay. But there was a group of plants that was actually in an environment with … there was sufficient light, but not an abundance of light, so making the wrong decision there could have been more critical. And as you can guess, what the plants do is, like, when they are in good environments, they take their time to learn. They still learn, but they are slower. And, you know, “Yeah. Whatever. I can drop another time.” While the ones that are in low light environments, of course, there is an urgency to get it right, because that could be … in a real scenario could be a really dangerous thing to do, if you don’t get it. And so, those plants learn very quickly.

MONICA GAGLIANO:         So it’s, “Ah! Excellent. Plants, it looks like they’re learning the trick!” So then what you do is, like, “I wonder how long they can remember this?” Because, of course, memory is not a separate thing; memory is an intrinsic aspect of learning. Learning is a process, and memory is one aspect of that process. So you leave them alone for a while, and then you come back. And you’re, like, “I’m going to disturb you again.” And the truth is that I … And this has happened to me a lot with plants. I don’t know if you guys have the same experience with your critters? But my plants just totally embarrass me every time. Because the question would be, like, “Would you remember what you had for dinner three days ago?” No? Exactly. Me neither. I don’t even remember what I had this morning. I have difficulty for breakfast.

MONICA GAGLIANO:         So I thought, like, “Three days. I come back in three days. That should be enough. They won’t remember.” And they did. Just as if we just did that. And then, so, “Okay. Then I come back in six days.” And, again, it was, like, “Ah! Yeah! We know this trick.” And I was, like, “Fine, then.” So I left them for a month. And not only that, but I divided my original groups, low light, high light, enough … some of the plants stayed in those groups where they … So the environment where they learned the trick remained the same as when, then I tested them a month later. But the other half of each group got swapped. Some plants learned in a low light environment, but then they found themselves tested in a high light environment, and vice versa.

MONICA GAGLIANO:         And so, suddenly, it’s like … So you learn the trick but it’s context dependent, so would you change what you’re doing? And what was interesting … many things were interesting. One, that after 28 days, the plants were, like, “Yeah. Yeah. It’s the drop. Would you stop it? I mean, it’s a bit annoying actually. So if you don’t mind. We got it!” So that was the first embarrassment. It was, like, “Okay. Great.” But the other really interesting thing was that for, of course, the plants that stayed in the environment where they were trained, they just perform as expected. The plants that went from a high light environment to a low light environment, so they learned in a comfy place, but then they found themselves in a not so comfy place, well, those guys suddenly behave as, like, “Oof! The environment has gone bad.” And so their response was very quick.

MONICA GAGLIANO:         But the interesting part was for the other group, the one that went from the low light environment to the high. And it was, like, “Now you can relax. The environment has gone good,” right? But they don’t. My suspicion is that what they are doing is, not only they are learning the trick and they remember it, but they are also learning another aspect of that context, which is the environment changes. The environment can change, and you went from bad to good once, so it can return to bad again. So they remain on alert, as if it’s, like, “Okay. Any time now, it could just go back that way, so we are ready.” They do this, and of course there is no brain, or neurons, and that is the part that is very disturbing for some!

NATALIE ANGIER:   It turns out, though, that they’re using some of the same sort of processes, like calcium signals which are, you know, how the brain cells are work in us.

MONICA GAGLIANO:         The real answer is that we don’t really know. That’s the truth. But then we can pretend, and we can look at some of the chemicals that, yeah, as you mentioned, some of the chemicals and some of the substances that we have targeted as … These are neurotransmitters. And then, suddenly, by giving the name neuro-transmitters, means that if you don’t have neurons you can’t have the transmitter. But in fact we actually share the same transmitters, and if we didn’t call them neuron, we would have saved ourselves a big pain, because they’re exactly the same.

MONICA GAGLIANO:         So a lot of things like, the famous things like dopamine, serotonin, and many other chemicals that, you know, we are quite familiar with, and interact with our synapses and brain function and all of that, are shared. But by calling them in a particular … So the language itself is already locking us up in a set of corners where, then, we need to come out of. And that’s when we find it uncomfortable.

TOM HORTON:        So our tongues have calcium channels, and that’s what makes them hot … with peppers. The calcium channels open up. So my tongue actually often has a brain that I wish it didn’t have! I say some crazy things. But I wonder if it’s similar? I mean, calcium channels seems to be, sort of, in a lot of places, right?

MONICA GAGLIANO:         Oh yeah.

SIMON GARNIER:    Yeah. They’re, like, ubiquitous, right?

MONICA GAGLIANO:         Yeah. They’re everywhere.

TOM HORTON:        Yeah. Yeah. So-

MONICA GAGLIANO:         And that’s what I mean.

TOM HORTON:        Not always neurotransmitters though?

MONICA GAGLIANO:         Exactly.

TOM HORTON:        Yeah. Yeah.

MONICA GAGLIANO:         But that’s the thing, that what it’s pointing at, when we look at it without being too hung-up to the language, like, who cares if it’s intelligent behavior or not? It’s, like, “What is he actually doing? And what is the function? Why is he doing that … What is he doing that for?” And then even how it’s done becomes quite, like, oh yeah. Yeah, this is how fast, when a plant … This is not my work, but it’s how fast a signal can move when a plant is under attack.

MONICA GAGLIANO:         So it’s just that we haven’t been able to see some of these responses, and because they are invisible literally to our eyes. This plant, in particular, which is the beautiful, lovely, Arabidopsis!

TOM HORTON:        It’s not a plant because they don’t form mycorrhizae!

MONICA GAGLIANO:         But these are kind of responses that, now, by playing with technology, we’ve been able to literally see. But they’ve been occurring all the time. And the speed at which they are occurring might not be the same in all systems, but it’s pretty fast. And relative to what is useful in the context of that organism, like for plants which are not in a hurry, that’s really fast.

NATALIE ANGIER:   In slime mold they also seem to learn-

SIMON GARNIER:    They do-

NATALIE ANGIER:   … and they also transmit that learning to others. Right?

SIMON GARNIER:    Yeah. What you’re referring to is one of the most fascinating experiments of the past year, in my opinion. It was done by Audrey Dussutour and her team, in Toulouse, in France. And I don’t know if we have a picture? It might be easier to explain. But it’s an interesting experiment of habituation as well, right? You have slime mold on the- the yellow mass at the bottom. And the then the top part is actually a platform with food. And in between there’s this bridge that actually contains salt. And slime mold doesn’t like salt. Like most cells, they don’t like to move on salty things because that pumps all the water out of them.

SIMON GARNIER:    And in this experiment, Audrey managed essentially to train the slime mold to learn to cross that dangerous bridge to get to the food. That’s not even, like, the coolest part of the experiment here. Right? Slime mold, if you have a cell of slime mold, you cut it in half. And you have two slime molds. And then you put them back together, they fuse, and you have one slime mold again. So that’s what she did, she essentially took this trained slime mold, cut a piece out of it, and then fused it with a slime mold that wasn’t trained. And that new, mixed slime mold, the part that was trained, the part that wasn’t trained, retained the memory, retained the behavior of the slime mold that was trained.

SIMON GARNIER:    And so, that was this fascinating mind-blowing idea that you can train a part of the organism, you cut it out, and then you mix it with a part of another organism that’s not been trained, and then there is transmission of that memory between the two organisms as they fuse with each other.

NATALIE ANGIER:   Where is that memory being stored?

SIMON GARNIER:    That is … We don’t know. You have to imagine this is a field that is … We’re still at the behavioral level. We’re looking at the behavior of these organisms. We’re trying to understand their behavior, and observe and quantify it. But we haven’t looked much into the molecular mechanisms, and what are the molecules that are storing that memory there? And we don’t know.

TOM HORTON:        I think this is great. In my work, as well, in the classes with my students, there are so many times when I say, “We really don’t know the answer.” They ask great questions. We really don’t know. But it’s a great time to be here, because we’re making incredible gains. We’ve got all these tools, we just need enough people to ask the right questions. And it’s a fascinating time, and I think on all of these, to be involved.

SIMON GARNIER:    I don’t remember the name of the person who said that, but, like, “Science is being at the forefront of ignorance.”

TOM HORTON:        Oh yeah!

SIMON GARNIER:    And I actually find that quote, like, the person who said that …?

TOM HORTON:        Isn’t that the name of this session?

SIMON GARNIER:    But we are really there. We don’t know what’s happening. But we are starting to have the technology and the tools and the all the molecular tools to be able to get into the mechanisms inside the cell. And I’m trying to figure where the cells store that memory. It’s probably not going to be stored the same way it is stored in neurons, or maybe it is, actually? I don’t know.

MONICA GAGLIANO:         That’s the thing is, like, what I find fascinating is that this system, because they are basal, so they are … if you imagine the tree of life, these guys are all pretty much sitting at the base of the tree, at the root of the tree. And so, in a way-

SIMON GARNIER:    Well, not technically. They’re all at the tips.

MONICA GAGLIANO:         Well, compared to us, they are. And in a way it’s almost, like, well, evolution likes to tinker with material and building blocks that are all available. Right? So, well, if these guys are doing all of these things, then the building blocks are already there. So how we memorize things at the most fundamental level plays with the same … it’s likely that it plays with the same building block, and understanding this system might actually help us understand better what we are doing, and with all the beauty of our brain and our neural system.

MONICA GAGLIANO:         And so, it’s a win-win situation. Because we understand these organisms better, and they might actually help us understand better what we are already trying to understand about the human itself, or the higher animals.

NATALIE ANGIER:   So getting into our Act 3, here. Which is collective intelligence. So we’re going to be talking about, not just creatures that you wouldn’t expect are intelligence, but the idea of bringing things together and having an intelligence just through collective action.

NATALIE ANGIER:   And so, we’re going to bring in the next two people. One of them is a MacArthur Genius Award winner, and professor of engineering at Princeton where she studies collective intelligence in bird flocks, fish schools, ants, honey bees, zebra herds, and robots. So please welcome Naomi Leonard.

NATALIE ANGIER:   And our final guest is a tropical biologist, author, and photographer. A research associate in the Department of Entomology at the Smithsonian Institution, and a visiting scholar at the Department of Human Evolutionary Biology at Harvard. Please welcome Mark Moffett.

NATALIE ANGIER:   So speaking of swarm intelligence, there are leaf-cutter ants, and I just actually was reading today that ants have the largest brain, per body mass, of anything. Is that true?

MARK MOFFETT:     Of anything?

NATALIE ANGIER:   Of any species?

MARK MOFFETT:     Well, I would guess humans have larger. But as Darwin said, the brain of an ant is the most marvelous atom in the universe, because of what it can do.

NATALIE ANGIER:   And so, can you talk a little bit about this amazing society of leaf-cutter ants, and how they function together?

MARK MOFFETT:     Well, the message I always give to folks is that ants are really marvelous because some of them, particularly ones with large societies like the leaf-cutters, are really much more like humans than chimpanzees. Ants have to figure out all kinds of problems that no chimpanzee has to deal with. The leaf-cutter ants as an example, there are lots of differences, they are aliens compared to us, but the similarities are marvelous. Leaf-cutter ants, for example, we have the video of them carrying leaves, build highways that are very marvelous things. They build about three kilometers of highway a year in some colonies.

MARK MOFFETT:     These are pictures of mine from the air, in Paraguay, showing nests which are as a big as this room and as deep as this room, so these nests are enormous. And that white sand is just something they’ve brought up from deep below ground. And those are highways going out in all directions. And they’re carrying back those leaves you just saw in that previous video. And so, in the next picture, we can see what happens. This is below ground. As I say, very complicated architecture. All kinds of work going on there, by the ants. Just, we’re excavating into this, while these soldiers are ripping up our skin. And they have an air-conditioning system that keeps everyone cool, and oxygen into those all those chambers.

MARK MOFFETT:     And the next slide demonstrates what they’re doing. And you may not guess why they’re doing it quite yet. Maybe you know? But they cut up these leaves. Their jaws are about 40% zinc, so they’re literally can-openers that cut the leaves like this; they actually vibrate their bodies like electric carving knives. This is a certain kind of ant that’s good at this task, and it carries it back to the nest. It turns out, I think it’s shown in the next slide, that they do not eat leaves. It was thought for a while that they might.

MARK MOFFETT:     But what they do is that they’re agricultural species that are raising a fully domesticated fungus … thank you! This is a fungus that was domesticated many millions of years ago. And the ants have all the elements that you might think of as farming going on here. First, well, they have special problems; they have to reduce those leaves, in this case grass stem, as you can see, to a mulch, and then insert fresh fungi, hyphae, in those places, like a farmer would put baby plants down. And then they have to deal with various pests, so they have pesticides and fungicides that get rid of anything that doesn’t suit them.

MARK MOFFETT:     And every size of ant, and there are different sizes that do different duties, has a different one of these tasks. The leaf-cutting ants are relatively large, and you go down and down in size to the smallest ants, are actually involved with keeping those gardens pure; plucking out anything that doesn’t belong there. And the next slide shows that smallest ant doing that task.

MARK MOFFETT:     And this is a domesticated fungus. They domesticated this fungus about 40 million years ago, and it became fully dependent on the ants. And like domestication in humans, it means that we’re doing all the work. The fungus are getting a free-ride like the wheat plants are. The wheat plants have conquered the universe because of us. There’s so many more wheat plants than anything else. And these fungi actually have little nodes on the tips that have the complete and balanced diet of the ant in them. Those little white blobs there, that you see in the face of that ant, gives them anything they need.

MARK MOFFETT:     Next? So this is just going through the story. Now, the communication of these ants, they’re not brainless, but it’s pretty small! And involves simple signals. I’m particularly in identity. How these societies stay apart.

SIMON GARNIER:    It sort of makes sense. They have more muscles in their head than they have brains, actually, right?

MARK MOFFETT:     They do. Yes. And I would think that, you know, I feel like I’m comfortable with that.

TOM HORTON:        There’s an analogy!

MARK MOFFETT:     The smallest ones probably don’t, but the soldiers definitely do. The soldiers are big and dumb! And they just know how to cut you up as if you were a leaf.

MARK MOFFETT:     And most of these cues are signals going back and forth between them as they touch each other. And ants can actually determine many things when they’re walking down the trails, and you see them stop for a second in front of each other, they actually can determine … shown for some species, what the other ant is doing. And they will assess as they go on, what the ants in the colony are doing by the ones walking by, and decide themselves what they’re going to do that day. And so, this leads to a very efficient society, right down to the last detail.

MARK MOFFETT:     On the last slide, here, I said that ants are doing all kinds of things that chimpanzees don’t do. And I can tell you one thing chimpanzees don’t do is worry about public hygiene and health issues. And this is an ant that’s a trash collector. You can become a full-time trash collector in an ant colony! And believe it or not, you can become a specialist at old trash, or new trash, and moving dead bodies to the grave site; that’s a job. And burying this stuff about thirty feet down in some of these large colonies, which is the equivalent to us putting our worst hazardous waste three kilometers below ground.

MONICA GAGLIANO:         Don’t give bad ideas!

MARK MOFFETT:     Oh yeah! And they build these chambers just for the wastes, that are as big as a coffin for a small child. Not a nice image but … pleasant inside! And you can imagine how many millions of years combined, of all these thousands and thousands of ants, it takes to make a chamber that big, that far underground, just for public health reasons. And the reason for that is the diseases that that might carry could destroy the gardens. And these ants live and die down there, producing this into a mulch that becomes harmless.

MARK MOFFETT:     So that’s some of the story of how these particular ants work. Which are among, of course, the more complicated species out there, which is why I picked them out.

NATALIE ANGIER:   So who’s making the decisions? I mean, who’s the boss?

MARK MOFFETT:     Now, and a super-intelligent ant would wonder, “What the heck humans are doing?” Apparently, we keep some guy in the White House, and if we just take them out, we can, like, take over the whole country. What is that about? I mean, have you ever tried to stop ants? You can step on them all day in your kitchen and they’re just going to keep coming. And having no leader is a way of being very functional, as long as you’re organized enough, and everyone has enough information to make the right choices appear in aggregate, out of all these individuals.

NATALIE ANGIER:   Do you think of each individual ant as, like, a neuron?

MARK MOFFETT:     Well, it’s a interesting thing because, basically, a large ant colony … an ant colony like the leaf-cutter ants, or a large army ant swarm, has an aggregate, the same number of neurons that we have in our head, but distributed among many individuals. And so, you can ask yourself, what leads to the best result? Putting all our eggs in one basket, so that a single bullet to our head can destroy us, or distributing ourselves? I think of it as a kind of Marvel Comic superhero. Imagine if you could fall apart into a million pieces. You’re starving to death, but you fall apart into a million pieces, and these little mini-brains go out and find food that you could never find underneath things, feed you, and they come back together. And there you again, and you start composing music, or whatever you can do with your brain in one place.

MARK MOFFETT:     Only ants and humans have societies of millions, and sometimes billions, of individuals. And once you have a lot of individuals, you have to deal with public health issues, in the way that no other vertebrates other than humans does. It has nothing to do with intelligence. It has to do with the fact you have to put together a society that stays healthy, brainless or not.

NATALIE ANGIER:   Right. And Naomi, you’ve been studying collective behavior of other animals with small to middling-size brains, like ant swarms, honey bees, schooling fish, bird flocks.

NAOMI LEONARD:  Right.

NATALIE ANGIER:   What do you think we’re learning from looking at those kinds of swarming behaviors?

NAOMI LEONARD:  Like, these starlings are actually stunning. Not just beautiful, but remarkable in what they can do. I mean, they inspire me every day. I started working on these problems in the context of a design of sensor networks of robotic vehicles that would go into the ocean to collect data, and thinking about how I would instruct each one, program-up their computers so they would communicate and sense one another, and move in patterns to collect data.

NAOMI LEONARD:  And if you think about that, going into the ocean, it’s crazy hard. There’s so much uncertainty, so many things can happen. It’s so opaque. And to solve these kinds of problems, I had to make a swarm that would be sensitive to information in the environment that was important, and then also insensitive to all these uncertainties and perturbations and noise. When you look at these kinds of bird flocks, or fish schools, or ant colonies that forage in harsh environments … And I started talking with biologists, I learned that these animals actually balance this kind of trade-off between being able to be super-flexible, being able to be super-responsive to, and sensitive to signals that matter: a predator; food; a migratory route that they have to figure out. And then not be concerned with some kind of disturbance or false positive; it doesn’t throw them afoul.

NAOMI LEONARD:  And so, the questions that I’ve been looking at really reach into both contexts, and actually do use the connection between individuals as neurons, and a group as … or the swarm as a brain. Because there’s a lot in common in these settings. In the design setting, I’m asking these questions, “How do I give these individuals rules to respond to what they measure about the environment? To respond to what they sense about the neighbors that they can see or hear or communicate with? So that, at the level of the group, they’re flexible and responsive, but also robust?”

NAOMI LEONARD:  And in the animal world, the biologists that I work with ask the same kinds of questions, but the opposite direction. So they observe these behaviors, and they want to know what it is that individuals are doing. So what are the underlying responsive behaviors for individual fish, or an individual bird? How does it respond to what it senses about its neighbors?

NATALIE ANGIER:   Are they doing similar things? So, a school?

NAOMI LEONARD:  Yes. And it’s not just that they’re moving in beautiful ways, they’re actually moving to carry out tasks, or they’re carrying out tasks as they move together. So what might look like this aerial ballet, when you saw the-

NATALIE ANGIER:   Murmuration?

NAOMI LEONARD:  … the starling, the murmuration of starlings, is probably more likely an evasion of a predator, as a group. Or a foraging activity. Or sensing and learning about a migration route. And that’s just kind of remarkable, that they can do this.

NAOMI LEONARD:  So my work is involved in trying to understand, from a mathematical and physical principled perspective, what are those interconnections? What are the rules that animals are using? What is it about my neighbor that elicits a response? If Simon starts running this way, am I going to follow him? And what if Mark runs the other way? You know, do I split in half?

SIMON GARNIER:    Well, run this way, because Mark is …

MARK MOFFETT:     Yep. Don’t get us started!

NAOMI LEONARD:  Or the kinds of questions that you’re asking, what if there’s food over here, or there’s something scary over here, but my neighbor goes this way, should I do what this other plant is doing? Or should I go after what I think is better? So how does that work? In the case of the starlings, we asked these questions, if they’re in the middle of the flock and all they can sense are their neighbors, how is it that they’re ever going to be able to avoid the predator? So then, maybe, we have to understand what’s the shape of a flock? Because if the shape is like a big sphere, then the whole bunch of them are inside and don’t know anything. But if it’s more like a sheet, then almost everybody is, kind of, on the periphery and can know things.

NATALIE ANGIER:   So the number seven, I understand, is kind of an important number?

NAOMI LEONARD:  Yes. So in the case of the starlings, a group of physicists wrote a beautiful paper claiming that each bird was paying attention to it’s six or seven closest neighbors. And they explained that by looking where their neighbors were located. So the first closest, the second closest, the third closest, were in very particular places; they tended to be on the sides rather than front and back or top and bottom. But when they got up to eight and nine it just kind of didn’t matter, it was sort of arbitrary where you find the eighth or ninth.

NAOMI LEONARD:  And when I met them, they told me this whole story. And of course I asked them, “Well, why? So what’s special about six or seven? Okay, I believe you. Your argument seems plausible.” And so we went ahead and looked literally at these … If you take a whole set of points of where they are, and you draw arrows to the six or seven closest ones, you get a network. And then you say, for that network, if I give it some basic rules, how well will it perform sticking together, flying around like that, in the presence of uncertainty? And I can ask the same question, if they only pay attention to five, or four, or three, or eight, or nine, or 10? And what we found was that six or seven actually is, for the way they distribute themselves, the most efficient way to manage the uncertainty.

NAOMI LEONARD:  So it sort of … There’s evidence that there’s a reason for it. It might not be the only reason, but one can ask those kinds of questions using these kind of mathematics and physical principles.

NATALIE ANGIER:   Are you using that now in your work with robotics, too, this …?

NAOMI LEONARD:  Absolutely. Yeah. So the idea is to sort of extract out from what we learn through evidence in the natural systems and translate that into design. Because, honestly, the things that I learn that animals can do, I cannot imagine dreaming up a way to make it happen in the design world. Every day, fascinated and then inspired by new ways of doing things. And so, these same kind of rules we use to design our robots in the ocean and elsewhere. Absolutely.

TOM HORTON:        Is six and seven, maybe a number that’s related to how much brain it takes to pay attention to that many? You can’t go beyond that because it gets too complicated?

NAOMI LEONARD:  It could be. I mean, there’s still open questions about … This is a really important question, one that we look at, which is, like, “Who are your neighbors? Are you looking at them all the time? Are you constantly looking at six or seven? Are you kind of getting an average of where the six or seven are. Are you taking turns, maybe looking at this one, then this one, and this one?”

TOM HORTON:        You can summon memory, but not many can fit?

SIMON GARNIER:    You also have evidence now, like in fish and human beings, that we are actually not paying attention to particular individuals, but more like the movement that they perform on our visual field.

NAOMI LEONARD:  There’s also what you do with that information. I think, one of the things that we’re doing now, is not just relying on kind of, like, “Oh, you’re pulling me this way. You’re pulling me that way.” But through this analog with the neuronal dynamics, it’s that there’s sort of an excitability in the same way like a neuron firing excites another neuron to fire. So it’s not just that you pull me this way, but I’m more excited about whatever activity we’re doing because you’re excited. Or not? Or maybe you’re excited, I get less excited.

NAOMI LEONARD:  But it gives us a lot more meat, to be able to explain things like those super-fast movements that you see in fish schools, and cascades that you see. I mean, you can’t do that with these just sort of spring-like, you pull me this way, I pull you that way.

SIMON GARNIER:    That’s something that fascinated me in the birds, something you have to understand is they fly, maybe, 20, 30 centimeters apart, at 30- 35 miles per hour, and they can turn almost on the spot and they don’t collide with each other. And that’s something that … Like the speed at which the brain need to process that kind of information is just amazing.

NAOMI LEONARD:  Yeah. I mean, that’s an example of intelligence without a brain. The individual birds are not unintelligent, but the group-

NATALIE ANGIER:   … the swarm has its own intelligence.

NAOMI LEONARD:  Yeah. It’s bigger than the sum of its parts. It has its own intelligence.

MONICA GAGLIANO:         And I guess there is another element, kind of the other side of the coin, as well, is that not all individuals, although they are cooperating in this moving together, they’re all different.

NAOMI LEONARD:  Exactly. Exactly.

MONICA GAGLIANO:         So even those rules … Because of those differences, the rules remain flexible because of the individuality that is present in the group. Which is actually the power of the group.

NAOMI LEONARD:  Yeah. And I think that’s a new topic. I think people have been ignoring that for so long.

SIMON GARNIER:    I wouldn’t say they have been ignoring that. It’s just the methodology, the view … I mean, that’s going to need taking-

NAOMI LEONARD:  It’s challenging.

SIMON GARNIER:    The methodologies that were used, sort of, weren’t like … Averaged everything.

NAOMI LEONARD:  Exactly. Sort of squashed it-

MONICA GAGLIANO:         It reduced it. Yep.

SIMON GARNIER:    … squashed. In the modeling we used have squashed this variability. But it was there. It’s just at the time you didn’t have maybe the tools, or the computing power, to actually take into account the variabilities in your models.

MONICA GAGLIANO:         And I guess this what we actually do in general. Right? We look at our numbers, and we just trying to get those errors to be as small as possible, right? And of course there is a reason; you don’t want to have the error in your studies. But, also, some of that variability is exactly what makes that system work.

NAOMI LEONARD:  Exactly. I totally agree.

SIMON GARNIER:    It’s a general trend in the sciences right now, where you want to show the entire distribution of your data. Because a lot of the variability is actually extremely important to explain what-

MONICA GAGLIANO:         … what’s happening. Yeah. Yeah.

SIMON GARNIER:    If you just look at the mean, you actually miss a lot of the information. You can miss everything that’s happening at the extreme, which sometimes is … especially in our times, very important.

MARK MOFFETT:     Well, a lot of these things have to do with motion and space, and the relationships between organisms, in your case. To me, that’s really … One of the other things I work on is canopy biology, and that’s the formations of plants in a rain forest, or other communities. And you end up with this labyrinth, which is an architectural marvel, that various creatures have to move through. And some of them are the plants. I’ve worked a fair amount with some of the people working on them, and one fellow, Tom Ray, was working on the philodendrons.

MARK MOFFETT:     And they’re amazing, because what happens with the philodendrons is a bird will drop a seed to the ground, and it sprouts, and it moves directly towards the nearest tree trunk, in the dark, in the understory. Somehow it knows where that tree trunk is, presumably because of the quality of light. And it climbs up the tree, but what becomes amazing is that it grows two or three meters long and it loses the tail going to the earth. And it stays two or three meters long, and moves through the forest like a snake, in super-super-slow motion. And it has to choose where to go. And every bifurcation up there, all these labyrinths of architecture, it has to go through that. And what happens if it reaches a spot that’s in the shade, it grows very fast with small leaves. When it’s in a sunny spot, it grows these enormous leaves, like you see in the philodendrons in your doctor’s office.

MARK MOFFETT:     If it gets to the top of the tree, and tries to cross to the next tree, it’ll make a leader shoot that extends out and it will actually try to reach the next tree. It will grow out several feet and drop, and eventually hold onto the other side, and it’ll cross to the next tree. But if it loses its grip and falls … Now, if an orchid up in the top of a tree, falls to the ground, it’s dead. It’s not going anywhere. But these philodendrons simply uncoil themselves, moves to the nearest tree trunk, and start up again.

MARK MOFFETT:     And so, all these things, in the plant world too, are this dynamic thing, that if you could speed up time, there’s this life and death and chaos going on-

SIMON GARNIER:    I’m slightly panicked now!

MARK MOFFETT:     … everywhere. Thank goodness. There are trees that crush other trees to death, so you don’t want to be standing there for too many years!

TOM HORTON:        Just one more data point, that’s all I need!

NATALIE ANGIER:   So it sounds like we should move beyond the kind of neuronal brain-centered definition of intelligence? I mean, why have we been so neuronal? I think, Simon, I saw something where you were talking about how a neuron in a dish is a stupid thing, it doesn’t do anything, but we-

SIMON GARNIER:    It doesn’t do much. Yes.

NATALIE ANGIER:   Yeah. So we kind of imbue it with this power of consciousness, and all that. But it isn’t. It’s just a cell.

SIMON GARNIER:    Part of what biology is sort of getting at, right now, is the idea that the unit is not what’s important; it’s the interactions between the mini-units. So the intelligence doesn’t live in the neuron, but something is in the neuron, there’s some activity there. But what’s important is what this neuron is connected to, and how many of them … How the behavior of one neuron impacts the behavior of the other neurons. And if it’s properly set up, that can generate circuits and feedback, positive and negative, that then becomes the substrate for storing memories, or for remember things, or solving optimization problems, et cetera, et cetera.

SIMON GARNIER:    So I think that’s one of the big changes in the field of biology in general, but in science in general, over the past, I’d say, 20 years. Maybe. Yeah.

NAOMI LEONARD:  There’s this beautiful kind of … the scales kind of repeat. So that the elements at one level, at the fine scale, become the course here. But those, themselves, are the fine level for the next level up.

MONICA GAGLIANO:         A fractal-

SIMON GARNIER:    And at every level that’s-

NAOMI LEONARD:  … it just keeps going, right? Until you get to these populations of …

NATALIE ANGIER:   Right.

SIMON GARNIER:    And at every level it’s the interactions between these things, which creates what’s at the level above. And we are more and more understanding that it’s what … At least, that’s my personal opinion.

NAOMI LEONARD:  There’s a lot of open questions there!

SIMON GARNIER:    But the interaction is what is extremely important.

TOM HORTON:        I feel like the neuronal model is a good one, but it’s really familiar to us, and so we like it!

MONICA GAGLIANO:         I would stress that a little bit further. It’s not that it’s just familiar to us, it’s, like, it is all about us.

TOM HORTON:        We think it’s best.

MONICA GAGLIANO:         It’s, like, “It’s must be the best!”

TOM HORTON:        Yes. And, therefore, almost the only definition we’ve worked with for a while.

MONICA GAGLIANO:         Exactly.

TOM HORTON:        We need to expand that out.

MONICA GAGLIANO:         It’s a very anthropocentric space, basically.

TOM HORTON:        That’s one way to put it. Yes.

MONICA GAGLIANO:         And we just use that as the golden standard to measure everything against. Instead of, like, it’s just one model. And how beautiful. It’s not making it less, or more. It’s just, like, how beautiful. And …? The beauty is that there are so many other ways to do exactly the same task, in so many different combinations.

SIMON GARNIER:    You can always bring back everything to networks.

MONICA GAGLIANO:         Exactly.

SIMON GARNIER:    Interactions between all these different parts. So I think that’s where the neuronal model is not wrong. I mean, it’s not wrong because it is what it is, right? it’s a network.

MONICA GAGLIANO:         Yeah. It’s just a model.

SIMON GARNIER:    But we realize that, as long you have a network like this, whatever it’s made of, whether it’s made of neurons-

MONICA GAGLIANO:         Who cares?

SIMON GARNIER:    … who cares, exactly! These networks are going to generate this emergent property that sometimes intelligent.

NATALIE ANGIER:   Emergent? Yes. Consciousness-

SIMON GARNIER:    Sorry. I didn’t want to say the “E” word.

NATALIE ANGIER:   No, it’s a good word. What about consciousness? I mean, do you think that-

MONICA GAGLIANO:         … the “C” word?

NATALIE ANGIER:   The “C” word, yeah!

MONICA GAGLIANO:         I’m sorry that I can’t swear. I’m told not to swear, so I can’t talk about it!

SIMON GARNIER:    I think we’re going to turn around and let …

NATALIE ANGIER:   Do they have some self-awareness? I mean, is an ant self-aware? Is a tree self-aware?

MARK MOFFETT:     Well, one really interesting thing about … Am I self-aware? Get me a mirror!

SIMON GARNIER:    Thank you for taking the heat for everyone!

MARK MOFFETT:     One interesting thing about humans is we take a lot of information from our faces. So a person who has a neurological problem and can’t express emotion, we attribute to them fewer emotions.

MARK MOFFETT:     An attribute of ants, if you’ve looked at them closely, is they have fixed faces. So the question is, what’s going on there? And when I do photography of ants for National Geographic, with my research, too, and if I’m stalking an ant, I have a high magnification camera, and I’m looking at that ant behind a leaf, I can tell by how its body tenses and how it turns, that it knows that I’m there. And, basically-

MONICA GAGLIANO:         You mean, “He’s there”? He’s doing this?

MARK MOFFETT:     She! All she.

MARK MOFFETT:     But you know it’s interesting to know that because that’s how, if you look back at hunter-gatherers and descriptions of how they hunted, that’s how they dealt with other animals. Anthropomorphism was how we moved through the world. And if you do it smartly, you can learn things from it. And so, hunters would know from the footprints where that animal was going to go, whether it was in a hurry, whether it was horny: whatever was going on.

MARK MOFFETT:     And I’ve been with them, and it’s just amazing to see what information they pull up; maybe it’s not accurate, but it’s still gets them the result. And that, in itself, tells you something interesting, as a starting point for thinking about how those animals behave. And, maybe, plants. I don’t know if hunter-gatherers sitting around watching plant grow, but …

MONICA GAGLIANO:         I’m sure they did.

SIMON GARNIER:    Just for a long time. It’s very long.

NATALIE ANGIER:   One question I have about this, and that is, do you think that this has any ethical implications? If you’re going to have kill to eat, as we do, is it more ethical to kill a plant than an animal?

MONICA GAGLIANO:         Ethics belongs to a human world, so we should acknowledge that first. That we’re talking about, not what the plant feels or the animal feels, but when we talk about ethics we’re talking about how we behave towards the world.

NATALIE ANGIER:   Right.

MONICA GAGLIANO:         Right. And so, the question really is, like, are we justifying misconduct, our own behavior? Because if we are even asking the question, “Is this ethical?,” it’s maybe because we already know that it’s not, otherwise we wouldn’t be asking it. And maybe some people don’t ask it. And that’s okay. Maybe they have an easy life. But I think as a group, as a collective, obviously this question arises over and and over again, whether we’re talking about farming of animals, whether we’re talking about farming of plants. And so, the fact that the question is actually there is because, fundamentally, we have an issue with our behavior.

MONICA GAGLIANO:         And to me, I am vegan. And I have eaten animals. Then, not animals, but just as a vegetarian. And then I moved onto a vegan diet, just because my body decided so. What I understood for myself is that actually the main issue and the main reason why I had an ethical issue with eating animals was because of my lack of awareness of how these animals arrive to me. My mum still … We were talking about it this morning, afternoon, in a different session, my mum still thinks that salami is not an animal. And I’m, like, “I don’t eat meat.” And it’s, like, “Yeah. But this is salami!” “Okay. Then I don’t eat salami.” But that’s exactly the point, it’s like salami is not an animal. So I don’t have any need to worry about what the story is behind this.

MONICA GAGLIANO:         But when you actually concern yourself, or when you really tune-in with this body and you’re really interested to know, who are you? What is this? What are you made of? And I think, as a scientist, ultimately, the only question that we are all asking is, like, what is this? Life? Whatever. And so, the closest place that I’ve found for myself, personally, is the conversation via food. It’s, “Okay. I take these other, and I get it in here. And that other is making this, basically.” So even the concept of, like, I’m a human being, is, like, “Well, how much of this is actually plant material?” Really. Mostly. Because I only eat plants. And so, the question is, like, this transmutation of one organism into the other, which, well, suggests that actually we have … That the entire system is very porous and very mutable and volatile.

MONICA GAGLIANO:         But also, like, then, even more reason to be, not only respectful and appreciative of the fact that this other is going to make your body next, because your body is being revealed all the time. But also, well, then, you want to make sure that what you’re putting in here is actually clean and good and happy in a way. So you don’t want to eat an animal that has been through horror and suffering, because in a way that’s who you’re eating. And the same would be true for plants. So it’s not so much whether you’re eating meat or not, whether you’re eating the animal or whether you’re eating the plant, or both. It’s more, like, “Do you actually know who you are eating?” And if you don’t, then start thinking about it.

NATALIE ANGIER:   Okay. So I think we’re just about out of time. But I did want to take a couple of questions from the audience. So …

AUDIENCE:   I was wondering, much of what all of you mentioned has to be with collaboration, and collaboration being a trait for intelligence. Now, is that collaboration affected by the harshness of an environment? For example, the flock of birds, if they were in a super-comfortable position, would they still collaborate?

NATALIE ANGIER:   That’s a very interesting question.

SIMON GARNIER:    If we talk about the flock of birds, or, actually a lot of these flocks and schools is, the predominant theory to explain how they form, it’s because they were responding to predation. You can actually create a mathematical model, where if the only pressure you put is predation, they will evolve this schooling and flocking behaviors.

SIMON GARNIER:    So the question whether, if you relax that pressure they will go back to live by themselves, it’s possible because there’s a lot of cost of living in groups. Right? You have to compete for your food with people around you. You have to compete for the mates that are around you. You have to compete for space. There’s a lot of disadvantages, like infanticides in certain animal societies, et cetera.

SIMON GARNIER:    I mean, we see it, like nepotism is a form of that, in human societies, where we try to advantage or take advantage of the system for our kids.

NAOMI LEONARD:  But there are advantages too, though?

SIMON GARNIER:    There are advantages. But the question is-

NAOMI LEONARD:  So if you can’t find the food by yourself, and you need somebody else to find it …?

SIMON GARNIER:    So the question is if that’s predation that’s only driving the system, than, yes, this system will probably go back to being solitary. But then there are things, also, when you’ve reached this point where you live together, and in the case of, in the ants for instance, you reach this point where the advantages, when you pass that sort of like evolutionary hump, behind the hump there is so many advantages, that the original pressure can disappear and then you never go back.

SIMON GARNIER:    I mean, that’s what, like, you witnessed, probably, with your …

MARK MOFFETT:     Yeah. I just did a book on societies and where they come from, and what causes them to come together and fall apart. And society has groups with distinct memberships, those are extremely rare in nature. Most- 99% of the species are alone all the time, or just temporarily social when they need to be. So this is actually a tough hurdle but, as you say, once you get there, you can conquer the world.

MARK MOFFETT:     We, in ourselves, are societies, because our own bodies are consisting of cells that are totally in collaboration to get something done. So we are the most successful societies. All these large organisms that are around, the actual insects, and all the other large creatures that we see, mostly, are loners.

MONICA GAGLIANO:         And I guess, sorry, if I might add, it depends really, like we’ve been talking about time scales, but it also really depends what is the scale of the question. So, ultimately, this entire place is based on, primarily, collaboration. And competition is as important though. So competition creates that noise that is required to create the variability that allows for the system to be dynamic. And then it finds places where it can collaborate, our bodies are a good example, and places where things don’t collaborate very well.

MONICA GAGLIANO:         And in some situations, when that collaboration breaks down, as we know in our body, cancer does that very well, then it can kill everything. But actually life seems not to just die off like that, so maybe the two forces are working together.

MONICA GAGLIANO:         But I would say that collaboration is very important. Beyond just, like, it’s advantageous because when you are collaborating as a group, you can survive better from a predator.

TOM HORTON:        Leaving the population level, collaboration’s also …. the perceived collaboration is really important to mychorrhizal networks, and our microbiome. We’re not just human here, right? And so, there are a lot of functions, and a lot of, shall we say, niche space, that’s being fulfilled not by us but by other organisms in our bodies. And is that a perception or is that reality? Do the bacteria want our brains to get bigger? For instance. Just to put it in a very stark way.

NAOMI LEONARD:  I think it all goes back to heterogeneity and individual differences. So if we’re all going to be able to do the same thing, then maybe we don’t need to collaborate. But if we are different, and we have different expertise, then it makes a lot of sense.

NATALIE ANGIER:   Yeah. It sounds like ants with this super-specialized kind of …?

MARK MOFFETT:     Right. Which emerges as the colonies get bigger and bigger, and things get more and more complex. That’s when it becomes interesting. That’s when they become more and more … the parallels become more and more interesting with this.

TOM HORTON:        So there’s selective pressure towards a job?

MARK MOFFETT:     Not necessarily. There are ants, with huge colonies, where everyone is pretty much the same, but they’re not very interesting socially to study. But these leaf-cutter ants are among the most extreme. And as I said, you can tell what they do by their size, just as you can tell what people do by whether they’re wearing a hard hat and have the lunch pail, or are looking like a lawyer, or whatever. In ants, it’s size and shape.

MARK MOFFETT:     I’m just looking like I should be in the jungle! Ironically, where I should be.

NATALIE ANGIER:   Well, I think we have to wrap it up now. And I want to thank everybody for coming. It’s been great.

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Intelligence Without Brains

How much brain do you need to be smart? Bees and ants perform marvels as colonies, though each insect has barely any brain. And plants—with no brain at all—exhibit behaviors that, by any definition, count as intelligent. Brace yourself for a mind-bending exploration of plants that learn new behaviors and warn their brainless fellows of danger; vines that compete with each other; molds that solve puzzles; and trees that communicate and cooperate through a ‘wood-wide web’ of microscopic mycological fibers. Perhaps the real question is, are we smart enough to appreciate the vast range of intelligence that surrounds us?

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Moderator

Natalie AngierAuthor

Natalie Angier is a Pulitzer-prize winning science columnist for The New York Times and the author of Woman: An Intimate Geography—a finalist for the National Book Award—and The Canon: A Whirligig Tour through the Beautiful Basics of Science, among other books. She has also written for Smithsonian, The Atlantic, National Geographic, The American Scholar, Wired, Geo, Slate, and many other publications.

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Participants

Thomas HortonMycologist

Thomas R. Horton is professor of Mycology at the State University of New York, College of Environmental Science and Forestry. His research is focused on mycorrhizal fungi.

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Naomi LeonardControl Theorist

Naomi Leonard is the Edwin S. Wilsey Professor of Mechanical and Aerospace Engineering and associated faculty member of the Program in Applied and Computational Mathematics at Princeton University.

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Monica GaglianoEvolutionary Ecologist

Monica Gagliano is a research associate professor in evolutionary ecology. She is based at the University of Sydney as a Research Affiliate at the Sydney Environment Institute and a Senior Research Fellow at the School of Life and Environmental Sciences.

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Simon Garnier Biologist

Simon Garnier is an associate professor in the Federated Department of Biology at the New Jersey Institute of Technology and Rutgers-Newark. He is the head of the Swarm Lab, an interdisciplinary research lab that studies the mechanisms underlying collective behaviors and swarm intelligence in natural and artificial systems.

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Mark MoffettBiologist, Anthropologist

Mark Moffett began doing research in biology in college and went on to complete a PhD at Harvard. Moffett is known for documenting new animal species and behaviors during his exploration of remote places in more than a hundred countries.

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