[RADIOLAB INTRO]

ALVIN UBELL: Testing one, two. This is the headphones?

JAD ABUMRAD: I'm Jad.

ROBERT KRULWICH: I'm Robert.

LATIF NASSER: How is that? Better?

ROBERT: Oh, much better.

JAD: This is Radiolab.

ALVIN UBELL: Can I interrupt?

ROBERT: Yes.

ALVIN UBELL: Could I say ...

LARRY UBELL: Me first. Me first. Because if I let you go it's gonna be another 20 minutes until I get to talk.

ROBERT: A little while back, I had a rather boisterous conversation with these two guys.

ROBERT: First of all, like, who are you?

LARRY UBELL: I'm Larry Ubell.

ROBERT: Yeah.

ALVIN UBELL: And I'm Alvin Ubell.

ROBERT: So you are related and you're both in the plumbing business?

ALVIN UBELL: Are we related?

LARRY UBELL: Yes, we are related. But we are in the home inspection business.

ALVIN UBELL: Yeah.

ROBERT: They're father and son. It's a family business.

LARRY UBELL: We are the principals of Accurate Building Inspectors of Brooklyn, New York.

ALVIN UBELL: And I've been in the construction industry ever since I'm about 16 years old. I'm 84.

ROBERT: Okay.

LARRY UBELL: I'm not giving my age. [laughs]

ROBERT: I wanted to talk to them because, as building inspectors they—there's something they see over and over and over.

LARRY UBELL: Yup.

ALVIN UBELL: All the time.

ROBERT: That is actually a clue in what turns out to be a deep, deep mystery.

JAD: Which—which is what, exactly?

ROBERT: Well, let us say you have a yard in front of your house. Yours is back of your house, but let's make it in the front.

JAD: Okay.

ROBERT: And right in the middle of the yard is a tree.

ALVIN UBELL: And the tree happens to be a weeping willow.

ROBERT: And not too far away from this tree, underground, there is a water pipe.

ALVIN UBELL: A perfectly good pipe.

ROBERT: Connecting your house to the main city water line that's in the middle of the street.

JAD: Mm-hmm.

ROBERT: But the Ubells have noticed that even if a tree is 10 or 20, 30 yards away from the water pipe, for some reason the tree roots creep with uncanny regularity straight toward the water pipe.

ALVIN UBELL: The tree will wrap its roots around that pipe.

ROBERT: Around and around and around.

ALVIN UBELL: In a tangling of spaghetti-like, almost a—and each one of those lines of spaghetti is squeezing a little bit. Each one an ounce, an ounce, an ounce, an ounce, an ounce. Eventually over a period of time, it'll crack the pipe like a nutcracker.

LARRY UBELL: Yes.

ROBERT: The Ubells see this happening all the time.

LARRY UBELL: Yeah, and I have done inspections where roots were coming up through the pipe into the house.

ROBERT: Into the house?

ALVIN UBELL: It's amazing.

LARRY UBELL: Yes.

JAD: This—this actually happened to me. The magnolia tree outside of our house got into the sewer pipes, reached its tentacles into our house and busted the sewage pipe.

ROBERT: This happens to a lot of people. It's almost as if these plants—it's almost as if they know where our pipes are.

JAD: I see what's happening.

ROBERT: What?

JAD: Are you bringing the plant parade again? Is that what—is that what this is?

ROBERT: Well, of course I am.

JAD: You're doing the—like, okay. First it was the roots under the ground and all connected into a little hive thing.

ROBERT: I don't know why you have problems with this.

JAD: No, it's because it's like every time I close my eyes, you're coming at it from a different direction.

ROBERT: I do! I do!

JAD: With the plant parade.

ROBERT: And I met a plant biologist who's gonna lead that parade. She's done three experiments, and I think if I tell you about what she has done, you—even you—will be provoked into thinking that plants can do stuff you didn't imagine or dream they could do.

JAD: Hmm.

ROBERT: I know—I know you—I know you don't. But let me just—let me give it a try.

JAD: Okay. I'm game.

ROBERT: So let's go to the first. This is the plant and pipe mystery.

MONICA GAGLIANO: Hello, finally!

ROBERT: Hello! Hello, at long last!

ROBERT: Now, you might think that the plant sends out roots in every direction. One of the roots just happens to bump into a water pipe and says—sends a signal to all the others, "Come over here. Here's the water."

JAD: Right.

ROBERT: But that scientist I mentioned ...

MONICA GAGLIANO: My name is Monica Gagliano. I'm a research associate professor at the University of Sydney.

ROBERT: She took that notion out of the garden into her laboratory.

MONICA GAGLIANO: Yeah, tested it in my lab.

ROBERT: She took some plants, put them in a pot that restricted the roots so they could only go in one of just two directions, toward the water pipe or away from the water pipe.

JAD: What kind of pot is this?

ROBERT: It's kind of—it's shaped like ...

MONICA GAGLIANO: Like the letter Y but upside down.

ROBERT: So the roots can go either left or to the right.

JAD: Oh.

ROBERT: Now the plants, if they were truly dumb they'd go 50/50.

JAD: Right.

ROBERT: But after five days, she found that 80 percent of the time, the plants went—or maybe chose—to head toward the dry pipe that has water in it. So the question is ...

MONICA GAGLIANO: A plant that is quite far away from the actual pipe. How does it know which way to turn and grow its roots so that it can find the water?

LARRY UBELL: All right. My hypothesis is is that what happens is ...

ALVIN UBELL: No, I ...

LARRY UBELL: Can I have a few minutes?

ALVIN UBELL: No.

LARRY UBELL: You got somewhere to go?

ALVIN UBELL: No, because ...

LARRY UBELL: You got somewhere to go?

ALVIN UBELL: No.

LARRY UBELL: Good. If she's going to do this experiment, most likely she's going to use cold water. She's not gonna use hot water because you don't want to cook your plants, you know? And it's more expensive. Why waste hot water?

ROBERT: By the way, should we establish—is it a fact that you're—okay, go ahead. You want to contest.

ALVIN UBELL: He's—right track. You have to understand that the cold water pipe causes even a small amount of water to condense on the pipe itself. On the outside of the pipe.

LARRY UBELL: It's kind of like a cold glass sitting on your desk, and there's always a puddle at the bottom.

ALVIN UBELL: The glass is not broken. There's not a leak in the glass.

LARRY UBELL: It's not leaking. The water is still in there.

ROBERT: So there is some water outside of the pipe. It's condensation.

ALVIN UBELL: Right.

ROBERT: So what they're saying is even if she's totally sealed the pipe so there's no leak at all, the difference in temperature will create some condensation on the outside. And it's that little, little bit of moisture that the plant will somehow sense.

ALVIN UBELL: If you look at a root under a microscope, what you see is all these thousands of feelers like hairs on your head looking for water. Every one of them. And all of a sudden, one of them's like, "Woo-hoo-hoo! I found a little water!" And then all the other ones go in the same direction.

ROBERT: These sensitive hairs he argues, would probably be able to feel that tiny difference.

LARRY UBELL: Yes.

ROBERT: But Monica says ...

MONICA GAGLIANO: No.

ROBERT: Absolutely not.

MONICA GAGLIANO: I purposely removed the chance for a moisture gradient.

ROBERT: She made sure that the dirt didn't get wet, because she'd actually fastened the water pipe to the outside of the pot. So it wasn't touching the dirt at all.

JAD: Wait. So the—this branching pot thing.

ROBERT: Uh-huh.

JAD: The part where the water pipe was, the pipe was on the outside of the pot?

ROBERT: That's right. Outside.

JAD: And the plant still went to the place where the pipe was not even in the dirt?

ROBERT: Yeah.

JAD: That is strange.

LARRY UBELL: Or it's just the vibration of the pipe that's making it go toward it.

ALVIN UBELL: They would have to have some ...

ROBERT: Maybe there's some kind of signal? Different kind of signal traveling through the soil? Monica thought about that and designed a different experiment.

MONICA GAGLIANO: Again, if you imagine that the pot, my experimental pot.

ROBERT: With the forked bottom.

MONICA GAGLIANO: Yeah. But then have ...

ROBERT: Two very different options for our plant. On one side, instead of the pipe with water, she attaches an MP3 player with a little speaker playing a recording of ...

MONICA GAGLIANO: The sound of water.

ROBERT: And then on the other side, Monica has another MP3 player with a speaker. But this one plays ...

MONICA GAGLIANO: Nothing.

ROBERT: So she's got her plants in the pot, and we're going to now wait to see what happens. Remember that the roots of these plants can either go one direction towards the sound of water in a pipe, or the other direction to the sound of silence. On the fifth day, they take a look and discover most of the roots, a majority of the roots were heading toward the sound of water.

MONICA GAGLIANO: Exactly. Exactly.

JAD: So they just went right for the MP3 fake water, not even the actual water? Just the sound of it?

ROBERT: Just the sound.

LARRY UBELL: That—that's—that's interesting.

ALVIN UBELL: That's interesting.

LARRY UBELL: That is interesting.

ROBERT: But what—how would a plant hear something? Like, they don't have ears or a brain or anything like, they couldn't hear like we hear.

JENNIFER FRAZER: Well, maybe. They definitely don't have a brain. No question there. But they do have root hairs.

ROBERT: This is Jennifer Frazer.

JENNIFER FRAZER: I am the blogger of The Artful Amoeba at Scientific American.

ROBERT: And she was willing to entertain the possibility that plants can do something like hear.

JENNIFER FRAZER: So what do we have in our ears that we use to hear sound?

ROBERT: Little hairs!

JENNIFER FRAZER: Little hairs.

ROBERT: Yes!

JENNIFER FRAZER: Right? And if you go to too many rock concerts, you can break these hairs and that leads to permanent hearing loss, which is bad. So maybe the root hairs, which are always found right at the growing tips of plant roots, maybe plant roots are like little ears. Maybe each root is—is like a little ear for the plant. I don't know.

JAD: That is cool. That is definitely cool.

ROBERT: Hmm, okay.

JAD: And the thing I don't get is in animals, the hairs in our ear are sending the signals to a brain, and that is what chooses what to do.

ROBERT: That's true.

JAD: If a plant doesn't have a brain what is choosing where to go?

ROBERT: I don't think Monica knows the answer to that, but she does believe that, you know, that we humans ...

MONICA GAGLIANO: We are a little obsessed with the brain. And so we are under the impression, or I would say the conviction that the brain is the center of the universe, and—and if you have a brain and a nervous system you are good and you can do amazing stuff. And if you don't have one, by default, you can't do much in general.

JAD: But still, I mean, to say that a plant is choosing a direction, I don't know. I mean, it—like, when a plant bends towards sunlight.

ROBERT: Mm-hmm.

JAD: We've all seen houseplants do that, right?

ROBERT: Right.

JAD: Would you say that the plant is seeing the sun? No! I mean, it's just—it's reacting to things, and there's a series of mechanical behaviors inside the plant that are just bending it in the direction. I mean, couldn't it just be like that?

ROBERT: I think that that's fair, and I think if I move on to the next experiment from Monica, you're going to find it a little bit harder to object to it. We need to take a break first, but when we come back, the parade that I want you to join will come and swoop you up and carry you along in a flow of enthusiasm.

[LISTENER: Hi. This is Ashley Harding from St. John's, Newfoundland, Canada. Radiolab is supported in part by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at www.sloan.org]

JAD: Three, two, one, Jad.

ROBERT: Robert.

JAD: Radiolab.

ROBERT: Yep.

JAD: So today we have a triptych of experiments about plants.

ROBERT: Mm-hmm.

JAD: That apparently—jury's still out. Are going to make me rethink my stance on plants.

ROBERT: Yes.

JAD: So we're up to experiment two now, are we not?

ROBERT: That is correct. So we are going to meet a beautiful little plant called a mimosa pudica, which is a perfectly symmetrical plant with leaves on either side of a central stem.

MONICA GAGLIANO: Yeah, mimosa has been one of the test plants, I guess, for many scientists for, like, centuries.

ROBERT: Because this peculiar plant has a—has a surprising little skill.

MONICA GAGLIANO: Yeah. A reflex.

JENNIFER FRAZER: An anti-predator reaction?

MONICA GAGLIANO: Like a defensive mechanism.

JENNIFER FRAZER: As soon as it senses that a grazing animal is nearby ...

ROBERT: If a nosy deer happens to bump into it, the mimosa plant ...

MONICA GAGLIANO: Folds its leaves.

ROBERT: ... curls all its leaves up against its stem.

JENNIFER FRAZER: The whole thing immediately closes up and makes it look like, "Oh, there's no plant here. Just a boring set of twigs. Nothing delicious at all."

ROBERT: So the deer's like, "Oh, well. Never mind."

JENNIFER FRAZER: Right.

ROBERT: And you can actually see this happen. So ...

SHARON DE LA CRUZ: Okay, so ...

ROBERT: Anybody can get one of these plants, and—and we did. And if you just touch it ...

AATISH BHATIA: Can I try it?

SHARON DE LA CRUZ: Yeah, go for it.

ROBERT: ... even just one leaf ...

AATISH BHATIA: Like that?

ROBERT: ... you can actually watch this cascade ...

AATISH BHATIA: [gasps] Whoa!

ROBERT: ... where all the leaves close in like do-do-do-do-do-do-do.

AATISH BHATIA: Look at that. They all went closed.

ROBERT: It's sort of startling to see.

AATISH BHATIA: That's so eerie.

ROBERT: So that voice belongs to Aatish Bhatia, who is with Princeton University's Council on Science and Technology. We showed one of these plants to him and to a couple of his colleagues, Sharon De La Cruz ...

SHARON DE LA CRUZ: This guy or this guy?

ROBERT: And Peter Landgren.

PETER LANDGREN: Oh, that's neat!

ROBERT: Because we wanted them to help us recreate Monica's next experiment.

MONICA GAGLIANO: Okay.

ROBERT: So maybe could—could you just describe it just briefly? Just what you did?

MONICA GAGLIANO: Well, I created these horrible contraptions.

JENNIFER FRAZER: Apparently she built some sort of apparatus. I guess you could call it a mimosa plant drop box.

ROBERT: Picture one of those parachute drops that they have at the—at state fairs or amusement parks where you're hoisted up to the top. Except in this case instead of a chair, they've got a little plant-sized box.

JENNIFER FRAZER: Into which she put these sensitive plants.

ROBERT: So the plants are now, you know, buckled in, minding their own business. And then Monica would ...

MONICA GAGLIANO: Drop them.

ROBERT: Just about, you know, seven or eight inches.

MONICA GAGLIANO: Landing very comfortably onto a padded base made of foam. So no plants were actually hurt in this experiment.

ROBERT: [laughs]

ROBERT: But the drop was just shocking and sudden enough for the little plant to ...

JENNIFER FRAZER: Close all its leaves.

ROBERT: Its reflex defense thing. Then Monica hoists the plant back up again and drops it again. And again. And again. And after not a whole lot of drops, the plant, she noticed, stopped closing its leaves.

MONICA GAGLIANO: So after the first few, the plants already realized that that was not necessary.

JAD: The plants—the plants stopped—what is it they did?

ROBERT: They stopped—they stopped folding up.

JAD: Hmm.

ROBERT: She thinks that they somehow remembered all those drops and it never hurt, so they didn't fold up any more. They'd learned something.

MONICA GAGLIANO: Exactly, which is pretty amazing.

JAD: Couldn't it just be an entirely different interpretation here?

ROBERT: Like what?

JAD: The plants have to keep pulling their leaves up and they just get tired. They run out of energy.

JENNIFER FRAZER: Yeah, it might run out of fuel. Exactly. It's a costly process for this plant, but ...

ROBERT: She figured out they weren't tired. Because after dropping them 60 times, she then shook them left to right and they instantly folded up again.

JENNIFER FRAZER: It would close up.

JAD: Oh!

ROBERT: So it's not that it couldn't fold up, it's just that during the dropping, it learned that it didn't need to.

MONICA GAGLIANO: Yeah.

ROBERT: That's a—learning is something I didn't think plants could do.

MONICA GAGLIANO: They do.

ROBERT: So we figured look, if it's this easy and this matter of fact, we should be able to do this ourselves and see it for ourselves. So that's where these—the scientists from Princeton come in, Peter, Sharon and Aatish. They designed from scratch a towering parachute drop in blue translucent Lego pieces.

AATISH BHATIA: So this is our plant dropper. And we can move it up, and we can drop it.

ROBERT: So we strapped in our mimosa plant.

PETER LANDGREN: Little seatbelt for him for the ride down.

ROBERT: And then ...

AATISH BHATIA: All right. And then someone has to count.

ROBERT: I'll count.

ROBERT: And then we let it drop.

ROBERT: Five, four, three, two, one, drop!

ROBERT: And we dropped it once and twice. Again. And again. We were waiting for the leaves to, you know, stop folding. We dropped. We dropped. But it didn't happen.

JAD: It was curling each time when it ...

ROBERT: Every time. It just kept curling and curling. It didn't seem to be learning anything.

JAD: So you couldn't replicate what she saw?

ROBERT: Nothing happened at all. So we went back to Monica.

MONICA GAGLIANO: Yeah.

ROBERT: We, as you know, built your elevator.

MONICA GAGLIANO: I heard. [laughs]

ROBERT: We told her what we did.

ROBERT: What happened to you didn't happen to us. Now, can you—can you imagine what we did wrong?

MONICA GAGLIANO: Like, for example, my plants were all in environment-controlled rooms, which is not a minor detail. They're not experiencing extra changes, for example. I don't know if that was the case for your plants.

ROBERT: No, I—we kept switching rooms because we weren't sure whether you want it to be in the high light or weak light or some light or no light.

MONICA GAGLIANO: I wonder if that was maybe a bit too much. Was it possible that maybe the plants correctly responded by not opening, because something really mad was happening around it and it's like, "This place is not safe."

ROBERT: Truth is, I think on this point she's got a—she's right.

ROBERT: Oh no! [laughs]

ROBERT: One time, the plant literally flew out of the pot and upended with roots exposed.

AATISH BHATIA: This feels like one of those experiments where you just abort it on humanitarian grounds, you know?

ROBERT: So I think what she would argue is that we kind of proved her point. We were so inconsistent, so clumsy, that the plants were smart to keep playing it safe and closing themselves up. MONICA GAGLIANO: So actually, I think you were very successful with your experiment. You found exactly what the plants would do under your circumstances.

ROBERT: [laughs]

MONICA GAGLIANO: Which were, I don't know, let's say would be more tumultuous than mine?

ROBERT: And she goes on to argue that had we been a little bit more steady and a little bit more consistent, the plants would have learned and would have remembered the lesson. Because what she does next is three days later, she takes these plants back into the lab.

MONICA GAGLIANO: The idea was to drop them again just to see, like, the difference between the first time you learn something and the next time.

ROBERT: Like, would they figure it out faster this time? Or maybe slower?

MONICA GAGLIANO: Yeah.

ROBERT: So she takes the plants, she puts them into the parachute drop, she drops them. And she says this time they relaxed almost immediately.

MONICA GAGLIANO: Yeah, they remembered straight away.

ROBERT: Straight away.

MONICA GAGLIANO: All of them know already what to do.

ROBERT: They remembered what had happened three days before, that dropping didn't hurt, that they didn't have to fold up. So they didn't.

MONICA GAGLIANO: Yeah.

ROBERT: And then she waited a few more days and came back. They still remembered.

MONICA GAGLIANO: Yeah.

ROBERT: Few more days.

MONICA GAGLIANO: Yeah. And it was almost like, let's see how much I have to stretch it here before you forget.

ROBERT: Eventually, she came back after ...

MONICA GAGLIANO: 28 days.

ROBERT: 28 days!

MONICA GAGLIANO: Yes.

ROBERT: And they still remembered. They still did not close when she dropped them. That's what she says.

ANNIE MCEWEN: What was your reaction when you saw this happen?

ROBERT: That's producer Annie McEwen.

ANNIE: This retention of knowledge?

MONICA GAGLIANO: My reaction was, "Oh [bleep]!" That was my reaction. Because the only reason why the experiment turned out to be 28 days is because I ran out of time. So they might remember even for a much longer time than 28 days.

JAD: So she's saying they remembered for almost a month?

ROBERT: Yeah. I mean, can you remember what you were doing a month ago?

JAD: No, I actually—like, even this morning that's sort of like poof! Gone.

ROBERT: Exactly. Like, that's a thing.

JAD: Well, supposing that she's right.

ROBERT: Yeah.

JAD: Where would the—a little plant even store a memory?

ROBERT: Well, that's what I asked her.

ROBERT: I do want to go back, though, to for something like learning, like, I don't understand—learning, as far as I understand it, is something that involves memory and storage. And I do that in my brain. That's the place where I remember things. In my brain.

MONICA GAGLIANO: Or do you?

ROBERT: Yes, I do!

MONICA GAGLIANO: Do you?

ROBERT: Is a brain—I think.

[dog barking]

ROBERT: Is your dog objecting to my analysis? That's okay.

MONICA GAGLIANO: Picasso! Pics! Picasso! Enough of that! Pics, hey! It's okay, puppy. It's okay.

[dog barking]

MONICA: Oh, no! [laughs]

ROBERT: [laughs]

MONICA GAGLIANO: Picasso, enough of that now. Sorry!

ROBERT: Actually, Monica's dog leads perfectly into her third experiment, which again will be with a plant. But it was originally done with—with a dog.

JENNIFER FRAZER: So Pavlov started by getting some dogs and some meat and a bell.

ROBERT: Science writer Jen Frazer gave us the kind of the standard story.

JENNIFER FRAZER: And his idea was to see if he could condition these dogs to associate that food would be coming from the sound of a bell. So he brought them some meat.

ROBERT: They would salivate and then eat the meat.

JENNIFER FRAZER: Then he would bring them the meat and he would ring a bell.

ROBERT: And again, drooling, eating.

JENNIFER FRAZER: And he would repeat this.

ROBERT: Ring, meat, eat. Ring, meat, eat. Ring, meat, eat.

JENNIFER FRAZER: Finally, one time he did not bring the meat, but he rang the bell.

[dog barking]

JENNIFER FRAZER: Sure enough ...

ROBERT: The dogs began to drool.

JENNIFER FRAZER: They had learned to associate the sound of the bell ...

ROBERT: Which has, you know, for dogs has nothing to do with meat.

JENNIFER FRAZER: ... with when they actually saw and smelled and ate meat.

MONICA GAGLIANO: Exactly.

ROBERT: So that's a very—you know, animals do this experiment, but it got Monica thinking.

MONICA GAGLIANO: Would the plant do the same?

ROBERT: Could a plant learn to associate something totally random like a bell with something it wanted, like food?

MONICA GAGLIANO: Yeah.

ROBERT: Are you, like, aggressively looking around for—like, do you wake up in the morning saying, "Now what can I get a plant to do that reminds me of my dog, or reminds me of a bear or reminds me of a bee?"

MONICA GAGLIANO: Not really. [laughs] I guess that I feel—I feel sort of kind of good to say this. It's like, no, no. I don't—I don't do that.

ROBERT: But Monica says what she does do is move around the world with a general feeling of ...

MONICA GAGLIANO: Huh.

ROBERT: ... what if? So she decided to conduct her experiment.

MONICA GAGLIANO: Pretty much like the concept of Pavlov with his dog applied.

ROBERT: But instead of dogs, she had pea plants in a dark room.

MONICA GAGLIANO: Yeah.

ROBERT: And for the meat substitute, she gave each plant a little bit of food. In this case, a little blue LED light.

MONICA GAGLIANO: Light is obviously representing dinner.

ROBERT: So light is—if you shine light on a plant you're, like, feeding it?

MONICA GAGLIANO: Yeah, plants really like light, you know? They need light to grow. So otherwise they can't photosynthesize.

ROBERT: So for three days, three times a day, she would shine these little blue lights on the plants.

JENNIFER FRAZER: From a particular direction.

ROBERT: And she noticed that ...

JENNIFER FRAZER: Unsurprisingly ...

ROBERT: ... the plants would always grow towards the light.

JENNIFER FRAZER: Anyone who's ever had a plant in a window knows that.

ROBERT: And the salivation equivalent was the tilt of the plant?

MONICA GAGLIANO: Exactly. And then I needed to—the difficulty I guess, of the experiment was to find something that will be quite irrelevant and really meant nothing to the plant to start with. Like the bell for the dog.

ROBERT: So after much trial and error with clicks and hums and buzzes ...

MONICA GAGLIANO: All sorts of randomness.

ROBERT: ... she found that the one stimulus that would be perfect was ...

JENNIFER FRAZER: A fan.

MONICA GAGLIANO: A little fan. The same one that are used in computers like, you know, really tiny.

ROBERT: She determined that you can pick a little computer fan and blow it on a pea plant for pretty much ever and the pea plant would be utterly indifferent to the whole thing.

MONICA GAGLIANO: The plants didn't care.

ROBERT: Then she placed the fan right next to the light so that ...

MONICA GAGLIANO: The light and the fan were always coming from the same direction.

ROBERT: And with these two stimuli, she put the plants, the little pea plants through a kind of training regime. Little fan goes on, the light goes on. Both aiming at the pea plant from the same direction, and the pea plant leans toward them. Then she takes the little light and the little fan and moves them to the other side of the plant. Turns the fan on, turns the light on, and the plant turns and leans that way.

MONICA GAGLIANO: Yeah. Fan first, light after. And moved around, but always matched in the same way together.

ROBERT: Fan, light, lean. Fan, light, lean. Fan, light, lean. Same as the Pavlov. The bell, the meat and the salivation.

MONICA GAGLIANO: So then at one point, when you only play the bell for the dog, or you, you know, play the fan for the plant, we know now for the dogs, the dogs is expecting. So it's predicting something to arrive.

ROBERT: And Monica wondered in the plant's case ...

MONICA GAGLIANO: If there was only the fan, would the plant ...

ROBERT: ... anticipate the light and lean toward it?

MONICA GAGLIANO: Or would just be going random?

ROBERT: After three days of this training regime, it is now time to test the plants with just the fan, no light. So Monica moves the fans to a new place one more time. They're switched on. And the pea plants are left alone to sit in this quiet, dark room feeling the breeze.

MONICA GAGLIANO: And then ...

ROBERT: The next day ...

MONICA GAGLIANO: I remember going in at the uni on a Sunday afternoon.

ROBERT: And she goes into that darkened room with all the pea plants.

MONICA GAGLIANO: So, you know, I'm in the dark.

ROBERT: But she's got a little red headlamp on.

MONICA GAGLIANO: Yeah.

ROBERT: And she moves about the room.

MONICA GAGLIANO: To have a look ...

ROBERT: Peering down at the plants under the red glow of her headlamp.

MONICA GAGLIANO: And then I saw ...

ROBERT: That these little plants ...

MONICA GAGLIANO: ... my little peas ...

ROBERT: ... had indeed turned and moved toward the fan, stretching up their little leaves as if they were sure that at any moment now light would arrive.

MONICA GAGLIANO: And it's good it was Sunday. And I remember it was Sunday, because I started screaming in my lab. It was like, "Oh, I might disturb my plants!" I go out and I thought there's no one here on Sunday afternoon. I can scream my head off if I want to. And so I was really excited. I was like, "Oh, my God! These guys are actually doing it." And so, of course, that was only the beginning. Then we actually had to run four months of trials to make sure that, you know, that what we were seeing was not one pea doing it or two peas, but it was actually a majority.

ROBERT: So you just did what Pavlov did to a plant. You got the plant to associate the fan with food.

MONICA GAGLIANO: Yep. Pretty much.

ROBERT: But once again, I kind of wondered if—since the plant doesn't have a brain or even neurons to connect the idea of light and wind or whatever, where would they put that information? Like, how can a plant—how does a plant do that?

MONICA GAGLIANO: I don't know. I don't know yet. But what I do know is that the fact that the plant doesn't have a brain doesn't—doesn't a priori say that the plants can't do something. The fact that humans do it in a particular way, it doesn't mean that everyone needs to do it in that way to be able to do it in the first place. There are multiple ways of doing one thing, right?

ROBERT: Huh. So we're really—like this is—we're really at the very beginning of this.

MONICA GAGLIANO: Yeah, I know. This way, there is often more questions than answers, but that's part of the fun as well.

ROBERT: Monica's work has actually gotten quite a bit of attention from other plant biologists.

LINCOLN TAIZ: Yes.

ROBERT: And some of them, this is Lincoln Taiz ...

LINCOLN TAIZ: I'm a professor emeritus of plant biology at UC-Santa Cruz.

ROBERT: ... say they're very curious, but want to see these experiments repeated.

LINCOLN TAIZ: It's a very interesting experiment, and I really want to see whether it's correct or not.

ROBERT: Us, too!

ROBERT: He's got lots of questions about her research methods, but really his major complaint is—is her language. Her use of metaphor.

LINCOLN TAIZ: Right.

ROBERT: For example, words like ...

LINCOLN TAIZ: Hearing.

ROBERT: Or ...

LINCOLN TAIZ: Learning behavior.

ROBERT: And this? He's not a huge fan of.

LINCOLN TAIZ: Yes. If you get too wrapped up in your poetic metaphor, you're very likely to be misled and to over-interpret the data. I mean, I—it's a kind of romanticism, I think. You know, it goes back to anthropomorphizing plant behaviors.

ROBERT: Mm-hmm.

ANNIE: But I wonder if her using these metaphors ...

ROBERT: Again, producer Annie McEwen.

ANNIE: ... is perhaps a very creative way of looking at—looking at a plant, and therefore leads her to make—make up these experiments that those who wouldn't think the way she would would ever make up. And therefore she might, in the end, see something that no one else would see. Is it ...

ROBERT: This is like metaphor is letting in the light as opposed to shutting down the blinds.

ANNIE: Yeah. Kind of even like, could there be a brain, or could there be ears or, you know, just sort of like going off the deep end there. But maybe it makes her sort of more open-minded than—than someone who's just looking at a notebook.

LINCOLN TAIZ: I think you can be open-minded but still objective. I mean, I think there's something to that. I think there are some cases where romanticizing something could possibly lead you to some interesting results.

ROBERT: So you're like a metaphor cop with a melt-y heart.

LINCOLN TAIZ: Yes.

LARRY UBELL: That—that would be an interesting ...

ALVIN UBELL: Don't interrupt. They have to—have to edit this thing together. Let him talk.

ANNIE: Yeah.

ALVIN UBELL: How much longer? Because I have an appointment.

ROBERT: All right, that's it, I think. Well, I have one thing just out of curiosity ...

ROBERT: As we were winding up with our home inspectors, Alvin and Larry Ubell, we thought maybe we should run this metaphor idea by them.

ROBERT: There's—on the science side, there's a real suspicion of anything that's anthropomorphizing a plant. They just don't like to hear words like "mind" or "hear" or "see" or "taste" for a plant, because it's too animal and too human.

ALVIN UBELL: Mm-hmm.

ROBERT: And the classic case of this is if you go back a few centuries ago, someone noticed that plants have sex.

ALVIN UBELL: Oh, yes.

ROBERT: That there was a kind of a moral objection to thinking this way. And I'm wondering whether Monica is gonna run into, as she tries to make plants more animal-like, whether she's just gonna run into this malice from the scientific—I'm just wondering, do you share any of that?

LARRY UBELL: No, I don't because she may come up against it, people who think that intelligence is unique to humans. And so I don't have a problem with that. I've been looking around lately, and I know that intelligence is not unique to humans. Okay? So I don't have an issue with that. And every day that goes by, I have less of an issue from the day before. So I don't have a problem. The problem is is with plants. They may have this intelligence, maybe we're just not smart enough yet to figure it out.

JAD: Well, okay. That's a parade I'll show up for.

ROBERT: Okay. Let's do it! Big thanks to Aatish Bhatia, to Sharon De La Cruz and to Peter Landgren of Princeton University's Council on Science and Technology. Also thanks to Christie Nell and to Emerill O'Brien and to Andres O'Hara and to Summer Rayne.

JAD: You're thanking summer rain?

ROBERT: [laughs] I am.

JAD: Did the plants sneak that one in?

ROBERT: [laughs] No. No, Summer is a real person. And her last name happens to be spelled R-A-Y-N-E.

JAD: Oh, okay. I see.

ROBERT: This story was nurtured and fed and ultimately produced by Annie McEwen. She actually trained this story in a rather elaborate experimental set-up to move away from the light and to a light breeze.

JAD: [laughs]

ROBERT: Against all its instincts. Oh, one more thing: thanks to Jennifer Frazer who helped us make sense of all this. You should definitely go out and check out her blog, The Artful Amoeba, especially to the post "The Forlorn Ones" about plants.

JENNIFER FRAZER: Plants are really underrated. [laughs] When I write a blog post, my posts that get the least traffic guaranteed are the plant posts. No matter how amazing I think that the results are, for some reason people just don't think plants are interesting. And to me, here are three more reasons that you can say, "No, really. Plants are amazing." And this world is amazing. And that living creatures have this ability for reasons we don't understand, can't comprehend yet, that's amazing and fantastic. And does it change my place in the world? Does it threaten my sense of myself or my place as a human that a plant can do this? No! Does it threaten your sense of humanity that you depend for pretty much every single calorie you eat on a plant? No!

ROBERT: So you think that—that this—you think this is a hubris corrector?

JENNIFER FRAZER: Yeah. I mean, what, so they can't move? Well, some of them can, first of all. And big deal. Can you make your own food? No.

ROBERT: [laughs]

[ANSWERING MESSAGE: To play the message press 2. Start of message.]

[JENNIFER FRAZER: My name is Jennifer Frazer.]

[LARRY UBELL: Hi, this is Larry Ubell]

[ALVIN UBELL: And Alvin Ubell of Accurate Building Inspectors.]

[JENNIFER FRAZER: And I am a science writer.]

[LINCOLN TAIZ: Radiolab was created by Jad Abumrad and is produced by Soren Wheeler.]

[JENNIFER FRAZER: Dylan Keefe is our director of sound design.]

[LARRY UBELL: Maria Matas—Maria Matasa—Maria Matasar ...]

[LINCOLN TAIZ: Maria Matasar-Padilla is our managing director.]

[JENNIFER FRAZER: Our staff includes: Simon Adler, Becca Bressler, Rachael Cusick ...]

[ALVIN UBELL: ... David—David Gebel ...]

[LARRY UBELL: David Gerbel?]

[ALVIN UBELL: David Gebel. David Gebel ...]

[JENNIFER FRAZER: Bethel Habte, Tracie Hunte, Matt Kielty ...]

[ALVIN UBELL: Matt Kielly, Robert Krulwich, Annie McWen—or McEwen ...]

[JENNIFER FRAZER: Latif Nasser, Malissa O'Donnell, Arianne Wack ...]

[ALVIN UBELL: Pat Walters ...]

[LARRY UBELL: And Molly Webster.]

[JENNIFER FRAZER: With help from Amanda Aronczyk, Shima Oliaee ...]

[LINCOLN TAIZ: ... Nial Hughes, Jake Arlow, Nigar Fatali ...]

[JENNIFER FRAZER: Phoebe Wang and Katie Ferguson.]

[ALVIN UBELL: Our fact-checker is Michelle Harris.]

[JENNIFER FRAZER: And lastly, a friendly reminder: have you hugged your houseplant today?]

[ANSWERING MACHINE: End of message.]

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