#166 Are Plants Conscious? - Michael Pollan

Within Reason

In this episode, Michael Pollan and Alex O'Connor explore the boundaries of sentience by investigating whether plants possess a form of consciousness.

Key takeaways

Michael Pollan distinguishes between sentience (environmental awareness) and consciousness (subjective interiority).
Plants like Mimosa pudica demonstrate memory by learning to stop reacting to harmless stimuli after 30 days.
Biologist Michael Levin's research suggests that bioelectric fields, rather than just neurons, can store information and organize biological life.
The concept of 'Umwelt' illustrates how every species inhabits a world uniquely shaped by its specific sensory apparatus.
The discussion addresses the 'hard problem' of consciousness, noting that finding neural correlates does not explain why experience feels like something.

Main topics

Plant sentience and neurobiology
Bioelectric fields vs. neurons
The Hard Problem of Consciousness

Notable quotes

If it is like something to be you... then you are conscious.

Conclusion

The episode serves as a profound meditation on the limits of materiali

Transcript preview

Speaker 1 (0:00) North America, I'm coming for you. We're doing a small tour, just six shows at some really cool venues. We're going to talk about philosophy. We're going to talk about God, about consciousness. We're going to talk about whatever you want to talk about because there will be an extensive Q &A at every show. The dates are on screen. The ticket link is in the description. Be there. I talk about the fine-tuning argument for God quite a lot. And there are so many debates back and forth. And it's like, well, you know, the Earth is well distanced from the sun, but there are billions of planets and one of them is going to be about right. And they write about the cosmological constant. And I'm like, well, I'm not sure that the upper bound has been properly calculated. And when someone points out that the moon is exactly 400 times closer than the sun, but it's also exactly 400 times smaller. So we get this perfect eclipse of totality, which isn't only perhaps the most beautiful thing I've ever seen. without a close second, but also just so happens to be integral to proving Einstein's theory of relativity. And so it has this sort of functional effect as well. And someone says, well, what are the odds of that? And I think, you know what? Fair enough, score one for God there. I can't quite get around that. And the very existence of the moon, right? Without which you would not have life on Earth. I know. It's all pretty extraordinary and also explains why to... the viewers who are watching this, I'm in a hotel room because I'm in a sort of random town in Spain that I'd never heard of before. It happened to be in the path of totality. And I'm now speaking to you, Michael Pollan from a hotel room, but I'm glad that we could make this work. So welcome to the show. It's good to have you here. Thank you. I envy the fact you're there and wish I could have made it. It was extraordinary. I was just telling you that I don't think I've ever been so... so moved by an astronomical event in my life and i spent about an hour watching the moon sort of track its way across the sun with the glasses on and i thought you know that's pretty cool yeah neat like that's pretty cool we're on a rock in space but in that moment of totality something happens and suddenly you're like staring into a black hole or something and it was it was moving in a way that i can't i can't quite describe but um there are all kinds of experiences that give people that mysterium tremendum at batting hands. And that's one of your specialties, I believe, is trying to come to terms with them. We're going to talk about experience today. You've written a wonderful book called A World Appears, which is... which is lifted from the beginning of Anil Seth's book, right? Speaker 2 (2:27) Yeah, it's the first line of one of his chapters. And I read his book when I was researching mine, and that sentence just stuck with me. And then I thought, well, I'm going to use that as my title. And by then I'd forgotten where I'd read it. But thank God for Google, I was able to put it in, and Anil Seth came up right away. I'm sure he didn't mind. No, Speaker 1 (2:52) he Speaker 2 (2:52) was fine about it. Speaker 1 (2:55) Yeah. I've spoken a lot about consciousness on this show. I want to open with something a bit broad and something which I don't think, for all I've spoken about consciousness, I've really talked about before on this show. What is it like to be a plant? We don't know. Speaker 2 (3:13) The question is, is it like anything to be a plant? And we don't even know that. You know, the what it is likeness is Thomas Nagel's, I don't know if you'd call it a definition, but a very effective way of thinking about consciousness. If it is like something to be you, and in his example, is it like anything to be a bat, then you are conscious. That is the standard. Your toaster, it's nothing. You know, it's not like anything to be your toaster. Speaker 2 (3:50) But he doesn't require us to know exactly what it is like to be a bat. We can just infer it's like something to navigate the world using sonar rather than light. But in the case of plants, it's a harder one. You know, I spent a long time researching what's sometimes called erroneously the neurobiology of plants and whether plants are conscious. They have some incredible abilities that I wasn't aware of. They can be taught things. They can be conditioned. They can learn and remember. They have something like 20 senses to our five or six. Speaker 2 (4:38) They can hear. You play the sound of caterpillars chomping on leaves and they will react appropriately. They'll dispatch chemicals to their leaves that make them taste less good to caterpillars. And kind of most bizarre and suggestive of all is they respond to the same anesthetics we do. So the kind of chemicals we use to put us out for surgery. will stop behavior in a plant that has a visible behavior, like a Venus flytrap. That's really interesting and suggestive because what it suggests is that, or it makes you ask, what is lost? Speaker 2 (5:28) When the plant becomes, I don't want to use the word unconscious, but something, there are two states. And if there are two states, what is that more active state? Is it a state of awareness? So those are the kind of questions I got into at the beginning of the book. I interviewed people who were convinced plants are conscious. I'm a little more comfortable using the word sentient. And in my work, I drew a distinction between sentience and consciousness. Sentience being a more basic, widely distributed capability that it's possible, and many people believe, you know, all life has sentience. Sentience is awareness of your environment, the ability to distinguish good or bad changes as they affect you. and then to respond appropriately, intelligently. And you find this in bacteria and single-celled creatures. So I'm inclined to think that plants are sentient after the research I've done. Consciousness just involves so much more, I think, this sense of experience and being able to... Speaker 2 (6:48) have, you know, some quality to your experience, you know, some interiority. And I don't know that plants have that. Speaker 1 (6:55) Yeah, I think it's a difficult thing to kind of wrap your head around, right? Because it sounds like the parody that people make when you start talking about why you shouldn't eat animal products and people say, well, what about plants? Because they can feel pain too. We're not talking about that, right? You introduce me. No, you Speaker 2 (7:09) know, it doesn't follow that, you know, that because you're sentient, you feel pain. Pain is one way of dealing with sentience, I guess, right? It's a tool that's very useful to animals. But one of the researchers I talked to said that pain would not be adaptive for a plant since it can't run away. Pain is very good when you have the option of removing your hand from the stove. And plants know they're being eaten, this guy said. His name is Stefano Mancuso. He's an Italian botanist. They know they're being eaten, but they don't necessarily mind. And he reminds us that for many plants, being eaten is part of their reproductive strategy, right? I mean, they produce all these seeds and fruits specifically to attract animals to move their genes around. And then you've got grasses, which... are regenerated by being chewed by ruminants they do better with ruminants than without so so it's a little too simple to um say they feel pain and i don't think we should worry about eating them um also because we don't have any choice yeah that's right if you rule out the plants and the animals all you have is salt and that's not Speaker 1 (8:27) a not a very well-rounded diet yeah exactly exactly um it just gives me a flashback from the debates where you would watch people's sort of smile fade as you remind them that actually the majority of plants that we grow are fed to livestock to then eat the livestock. So it's not a very good argument in that regard anyway. But I think the point is that if we're talking about or entertaining this idea of sentience in plants, it's got to be something quite minimal and restricted compared to our own experiences of the world. People will hear you say something like that and go, okay. What are we talking about? And they'll look in your book and there are some fantastic examples of like the bean plant, which if you watch time-lapse photography of this plant growing, it sort of looks as though it's striving towards a pole to grab onto. And when it gets it, it kind of relaxes a little bit. It's really interesting to see. There's evidence of plants which will seek out water in a pipe, even if that water is like contained within the pipe, implying that it's totally dry. Speaker 2 (9:26) Yeah, Speaker 1 (9:27) totally dry on the outside. So they must be able to somehow sense or hear it, probably something analogous to that. It's sort of going through the pipe. And this kind of stuff is absolutely extraordinary. But at the same time, somebody might say, well, look, you know, if I leave my bike out in the rain, then it rusts. And it's kind of amazing that it like reacts to the rain in this way. But you know, it's just a chemical reaction and no one thinks that requires anything like awareness. So what is it about the... the plant behavior that makes you want to say sentience rather than just chemical reaction, let's say. Speaker 2 (10:01) Well, your bike doesn't do anything about the fact it's being rusted. It doesn't move and get under a roof or anything. The plants actually take action. They move away. They move toward things. As soon as you look at plants using time-lapse photography, you realize that they're very active. And that bean plant is a good example. It would be completely... you would have no idea that it could see this post that it was looking for if you didn't use time-lapse photography. So even with time-lapse photography, I think your bike would be pretty boring to watch and wouldn't show. I mean, part of Sentience is the recognition of what's going on and then the... Speaker 2 (10:56) you know, taking action. You know, we used to think a lot, we used to talk a lot about instinct. Biologists would talk about instinct. And I found interviewing a lot of them for this book. You don't hear that word as much anymore. And the idea that behaviors were hardwired and programmed just doesn't work in a world that's changing in such unpredictable ways. And that even plants have to be intelligent because they often deal with situations they've never encountered before. And instinct is not useful in those situations. Speaker 2 (11:35) I think it was the biologist Michael Levin who said the way evolution really works is it creates cognitive beings with the ability to solve problems, not robots that are programmed for every eventuality. And I think that makes a lot of sense. I think that life demands that kind of flexibility and ability to make decisions. And we find that in these very simple creatures that we call very simple creatures. Of course, they're not. I mean, if we existed in the same time scale of plants, we would see a very different world. There's a wonderful science fiction plot that Stefano Mancuso shared with me. And it's a thought experiment. But imagine... an alien species comes to Earth and they live in a sped up dimension of time such that an hour of our time is a second of theirs. And they look at us and they see what he called immobile columns of meat that are, you know, as far as they could tell, are dead. And so they, you know, turn us into jerky for the ride home. And so we are that way with plants. We don't see all there is to see. And one of the most powerful ideas, I think, of biology is this idea of the umwelt, you know, that every species lives in a world conjured by its particular senses. And so the world of a bee is very different than ours because it can see ultraviolet light. And so it takes a tremendous... leap of imagination to put us into the unwelt of other creatures but when we do we realize there's a lot more going on than perhaps we we we gave them credit for yeah Speaker 1 (13:31) um all kinds of stuff which i mean the book is of course linked in the description you give a kind of overview that i'd known about this kind of stuff happening but hearing that plants can be taught to navigate mazes hearing that plants there's this plant i forget the latin name but it's cool it's known as like the sensitive plant right because it's sort of it like curls mimosa pudica That's why you're here. And it's fantastic. It will sort of react to its environment. It will like curl up and it's called the sensitive plant because it kind of wants to like hide away from certain sort of input data. But it can learn, like if you drop the pot, it will like curl up and it will learn that nothing actually came of that. Like actually that kind of feeling is just fine such that eventually when you do it again, it doesn't curl up anymore. And it remembers Speaker 2 (14:21) for 30 days that it needn't react to this stimulus, which is pretty wild because we assume memory is stored in neurons. But obviously there's another way to do it. And one theory is that in addition to neurons, there are these bioelectric fields in all biological creatures and that in those fields. you can hold information. Speaker 1 (14:50) And Speaker 2 (14:50) that might explain Speaker 1 (14:51) how they do it. Do you think that neurons as a key into understanding consciousness rather than just brain science are like overrated? I mean, you've made reference to these plant neurobiologists. It might have gone over people's heads that of course, like plants don't have neurons. Don't have any neurons. What's that all about? Speaker 2 (15:11) Well, those biologists are trolling more conventional botanists. who can't stand what they're doing and suggesting. They full well know that there are no neurons in plants. But you can do a lot of neuronal things without neurons. And this is a lot of the work of a biologist I interviewed several times for the book named Michael Levin at Tufts. And he has done these amazing experiments, including essentially creating new organisms. He'll scrape... the cells from tadpole skin and put it in a solution. And these cells... Speaker 2 (15:53) which have always been skin cells, will form clumps and they'll get together and they'll have a division of labor and they'll repurpose their flagella as a way to move and organize as a new organism. And there's nothing in their genes to tell them how to do that. And there are no neurons to keep it organized and remember because they can be taught to navigate mazes also. Really? So his project is really showing the limitations of both genes and neurons and that there are other things going on to organize life, to store memories, to communicate between cells. And a lot of that are these bioelectric fields, which we didn't really... We weren't able to study until really just a couple decades ago. We kind of knew they were there, but, you know. One of the things I learned studying science is that our observational tools, this is sort of like Umwell taken to another degree, but our observational tools dictate what we can see. And for a long time, we focused on the gene because the gene survived the death of the creature. And you could analyze, sequence its genome and learn a lot of stuff. Whereas the bioelectric field that the cell was part of, dies when the cell dies and it disappears. So in the 80s, I guess it was, scientists came up with these voltage-sensitive dyes that they could put on a mass of cells. And they saw that there was a lot going on. The colors were changing, there were patterns. And suddenly you saw a whole new dimension of biology that was invisible before. And the work on the bioelectric field has suggested these. alternative ways to do things that we thought you needed neurons to do. We'll Speaker 1 (17:58) get back to the show in just a moment. But first, one of the things that I'm conscious of is bias in news media. Wherever you look online, there's just an abundance of information. and it's difficult to know what you can trust. Bias is something that will never go away, but by using today's sponsor, Ground News, you can help to mitigate that bias by objectively comparing the way that different sources are reporting on the same stories. Ground News is a news aggregation service which brings together thousands of local and international news outlets. all in one place, so you can compare reporting across the political spectrum. Take a look at this story about a drought in Europe which is affecting crop production. Using Ground News, I can see that for whatever reason, of all the sources reporting on this story, only 11 % of them lean to the right, with 54 % of them, a majority... leaning to the left. Ground News also gives you a factuality rating for each of the sources, and it tells you who owns the sources as well. There's even a dedicated blind spot tab, which specifically seeks out stories that you would otherwise miss based on the news that you normally read. Try it out for yourself by going to ground.news forward slash alexoc, or by scanning the QR code that's on your screen. Use my link to get 40 % off that unlimited access vantage plan. And with that said, back to the show. What's the upshot of Speaker 2 (19:17) this? Speaker 1 (19:17) Because you begin your book in this way, and I chose to start our conversation in this way. Because personally, it's a bit shocking. It sort of grabs your attention. Plants maybe have sentience, sure. I thought it might destroy my credibility, actually. Speaker 2 (19:32) I'm Speaker 1 (19:32) glad it hasn't. I wasn't sure whether to ask you about that, just because I think you're in safe company here, so to speak. I was reading this thinking you've done an exceptional job at making me not feel like I'm reading a weird book because I love this kind of stuff. But when I read this kind of stuff, sometimes I'm reading the author and I'm like, dude, I'm totally on your side here, but you've got to understand how this comes across. You've done it really well, I think. But did you get any of that, like from the publishers or your agent or anything? Were they reading this going, yeah, I'm not so sure that we should go down this route, you know? I didn't, actually. Speaker 2 (20:05) You know, I'm hyper aware of that because I read those kind of books all the time. And I'm like, yeah, yeah, yeah. You know, this is too mystical for me. And I'm generally kind of skeptical about these non-materialist, but seemingly non-materialist explanations of things. Speaker 2 (20:27) And I'm used to writing for really straight publications like the New York Times Magazine and The New Yorker, whose tolerance for weirdness is pretty low. So I guess I've figured out how to approach it with the proper register of skepticism and enthusiasm. Yeah, Speaker 1 (20:47) I mean, I suppose part of it is that you present it as what it is, which is a mystery. in the service of some grand consciousness theory that you're going to sort of... That's right. Exactly right. Yeah. Instead, it's like, you know, there's no grand hypothesis here. There are just a number of facts which need explaining. And you can be a materialist. You can think that everything is reducible to atoms and physics. But you just need to account for certain features of the natural world. You know, plants can move towards pipes, which have running water inside of them. even though the outside of the pipe is dry. Implying what? That they can hear the water or something analogous? The question is just, if not, then what? How do you account for this kind of stuff? Plants can remember if they've been dropped, that it didn't harm them. Again, what else could be going on here? How else would you want to word what these plants are doing and demonstrably doing? We can observe them doing it. You do also hear about some unbelievable... And I mean literally unbelievable things as well, of course. Like what's that famous thing about how if you speak nicely to plants and, I don't know, send them positive energy that they somehow grow better? That stuff's a bit more dubious, shall we say. And annoyingly, that stuff also probably puts people off taking plant sentience seriously. But there are also just these... other well-documented plant behaviors, the kind of stuff that we've just been talking about, which do just occur.