No, plants don’t think

Figs in Winter
Dec 7, 2020 · 7 min read
Image for post
Image for post
[image: Solanum melongena, otherwise known as eggplant. One wonders what it’s thinking… Wikimedia Commons ; this is essay #253 in my Patreon/Medium series]

Plato famously suggested that the solution to societal problems was to put philosophers in charge. And his student, Aristotle, thought that the most sublime human life is that of… you guessed it! That of a philosopher! No surprise there, since both of them engaged in the profession that loves wisdom.

A lot of philosophers and scientists have a similar self-referential complex when it comes to thinking in general: panpsychists want to say that mental activity is a universal property of matter, despite the fact that there isn’t a shred of evidence of that being the case. And some scientists insist that non-animal organisms think as well, particularly plants.

One such scientist is Monica Gagliano, a senior research fellow at the University of Sydney in Australia. In a stupendously credulous article in the otherwise serious webzine Nautilus we are told that “plants are intelligent beings with profound wisdom to impart — if only we know how to listen. And Monica Gagliano knows how to listen.” We are then treated to a superficial summary of the evidence: Gagliano “has done groundbreaking experiments suggesting plants have the capacity to learn, remember, and make choices. That’s not all. [She] talks to plants. And they talk back. Plants summon her with instructions on how to live and work. Some of Gagliano’s conversations happened in prophetic dreams, which led her to study with a shaman in Peru while tripping on psychoactive plants.”

Oh boy. So now scientists use psychoactive drugs to discover new things about the world, even though we know perfectly well that such drugs cause hallucinations, not insights into deeper realities. Gagliano says in the article: “I did doubt my own sanity many times, especially when all these odd occurrences started — and yet I know I do not suffer from psychoses.” Of course that is precisely what someone suffering from (drug induced) psychoses would say.

Even a superficial reading of the Nautilus article clearly shows that a lot of Gagliano’s allegedly groundbreaking experiments are based on an equivocal use of language. For instance, “yes, that’s what they’re doing. This is definitely memory. It’s the same kind of experiment we do with a bee or a mouse. So using the words ‘memory’ and ‘learning’ feels totally appropriate. I know that some of my colleagues accuse me of anthropomorphizing, but there is nothing anthropomorphic about this.”

Actually, that’s pretty much all Gagliano does: anthropomorphize. I have worked with plants for decades, specifically studying a phenomenon known as “phenotypic plasticity,” the ability of plants with the same exact genotype to display different morphologies or physiologies in response to different environmental conditions. Plant biologists, myself included, refer to plasticity as “plant behavior,” but we don’t mean this literally. It is a shorthand for an alternative adaptive strategy that differentiates the animal from the plant world: animals properly “behave,” because they are capable of movement. Plants are literally rooted to their spot (and don’t have brain-induced electrochemical reactions powering muscles) so they evolved a different strategy to cope with the same problem: heterogeneous environmental conditions.

“So plants can hear water?,” asks the Nautilus interviewer. “Oh, yeah, of course. And I’m not talking about electrical signals.” Then you are not actually talking about hearing either, you are talking about an entirely different type of perception. Which, incidentally, is well understood. Nobody has ever denied that plants perceive and adaptively respond to their environment. They ought to, on penalty on not surviving and reproducing, the ultimate currencies of the Darwinian world. But it is only through ambiguous and obfuscatory use of language that Gagliano can make it appear like her discoveries are extraordinary.

Here is another example: “You are describing a surprising level of sophistication in these plants. Do you have a working definition of ‘intelligence?’” “That’s one of those touchy subjects. I use the Latin etymology of the word and ‘intelligere’ literally means something like ‘choosing between.’” By that standard, everything living, including bacteria and even sub-cellular components like ribosomes are “intelligent.” But since when scientific terminology relies on the etymology of a word that has been used for thousands of years — that is way before the birth of modern science — and disregard the more precise, modern technical meaning?

Gagliano continues: “I have written a paper with the title ‘The Mind of Plants’ and there is a book coming called The Mind of Plants [naturally]. In this context, language is used to capture aspects of how plants can change their mind, and also whether they have agency. Is there a ‘person’ there? These questions are relevant beyond science because they have ethical repercussions.” Indeed, which is why Gagliano and others shouldn’t use this sort of sloppy language! If she is right (and she ain’t) then vegetarians and vegans would be in the same boat as carnivores. Sorry, folks, plants have a mind, so you better start eating rocks. Except that those too also have a mind, of sorts, according to panpsychists. We’re out of luck!

And then she goes off the deep end: “I had this weird series of three dreams while I was in Australia doing my normal life. By the time the third dream came, it was very clear that the people that I was dreaming of were real people. They were waiting somewhere in this reality, in this world. And the next thing, I’m buying a ticket and going to Peru and my partner at the time is looking at me like, ‘What are you doing?’ [laughs] I have no idea, but I need to go. As a scientist, I find this is the most scientific approach that I’ve ever had.” Problem is, that is really, really bad science, Monica.

Here is yet another instance of nonsense arising from what I can only infer is willful misuse of language: “Of course, all plants are psychedelic. Even your food is psychedelic because it changes your brain chemistry and your neurobiology all the time you eat.” Not at all. “Psychedelic” means a specific thing, it is not equivalent to just any change in brain chemistry. Gagliano here is playing Humpty Dumpy in Lewis Carroll’s Through the Looking Glass:

‘When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less.’

’The question is,’ said Alice, ‘whether you can make words mean so many different things.’

’The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.’

The interview concludes with this stunning declaration by Gagliano: “It’s my truth. This is how I operate. This is who I am. And nobody has the right or the authority to tell me that it’s not real.” Oh yes we do, my friend. That’s how science works. You are entitled to your opinions, but unless they are backed up by commensurate evidence those opinions are fair game for others to criticize and dismiss. Whether you like it or not.

Indeed, one such detailed criticism of Gagliano’s and other people’s “research” has been co-authored by Lincoln Taiz, Daniel Alkon, Andreas Draguhn, Angus Murphy, Michael Blatt, Chris Hawes, Gerhard Thiel, and David G. Robinson and published in Trends in Plant Science with the title “Plants Neither Possess nor Require Consciousness.”

The authors go in great detail through the evidence put forth by so-called “plant neurobiologists” and dismantle it bit by bit, on the basis of a combination of: (i) ambiguous use of language on the part of said plant neurobiologists (as I have repeatedly highlighted above); (ii) flawed experimental designs; (iii) inconclusiveness of empirical findings; and (iv) results that actually have better, more standard explanations.

Feel free to go through the Taiz et al. paper, though it does require a bit of a background in plant biology and experimental design. Here, however, are some of the highlights from their conclusions. Minimal commentary on my part in square brackets after each quote:

“Plant neurobiologists are hardly the first biologists to ascribe consciousness, feelings, and intentionality to plants. Parallel claims were made by the Romantic biologists of the 18th and 19th centuries. Romantic biology began as a rebellion against the Cartesian/Newtonian vision of a deterministic, mechanical universe operating entirely by physical laws and was codified in the writings of German philosopher Friedrich Wilhelm Joseph Schelling as Naturphilosophie. The ultimate goal of German Naturphilosophie was to demonstrate that nature, mind, and spirit are one.” [This is the peculiar disease, affecting also defenders of panpsychism, that I pointed out at the beginning.]

“Why is anthropomorphism resurgent in biology today? In the most extreme case, all forms of life, even prokaryotes, are said to possess consciousness. This new wave of Romantic biology appears to have been inspired by a justifiable concern about humanity’s continuing ecological degradation of the biosphere: the loss of habitats and biodiversity, the over-exploitation of natural resources, and the crisis of climate change. Plant neurobiology has its roots in plant ecology and its philosophical offshoot, the Gaia hypothesis, rather than plant physiology, and an ethical perspective permeates its intellectual foundation.” [On the Gaia hypothesis, see this criticism of mine, and stay tuned for a new article on that topic coming out soon…]

“While we agree entirely that biodiversity needs to be protected, we strongly object to the implication that plant consciousness, intentionality, and cognition are moral or ethical questions. A scientific understanding of nature requires only that we seek the truth.” [Indeed.]

Science and Philosophy

Sign up for Science and Philosophy

By Science and Philosophy

Collections of the best scientifically-informed content on medium. Take a look.

By signing up, you will create a Medium account if you don’t already have one. Review our Privacy Policy for more information about our privacy practices.

Check your inbox
Medium sent you an email at to complete your subscription.

Figs in Winter

Written by

Stoicism, ethics, and philosophy of science. Complete index, by subject, at https://figsinwinter.blog/essays/

Science and Philosophy

Medium’s center for scientifically-informed content.

Figs in Winter

Written by

Stoicism, ethics, and philosophy of science. Complete index, by subject, at https://figsinwinter.blog/essays/

Science and Philosophy

Medium’s center for scientifically-informed content.

Medium is an open platform where 170 million readers come to find insightful and dynamic thinking. Here, expert and undiscovered voices alike dive into the heart of any topic and bring new ideas to the surface. Learn more

Follow the writers, publications, and topics that matter to you, and you’ll see them on your homepage and in your inbox. Explore

If you have a story to tell, knowledge to share, or a perspective to offer — welcome home. It’s easy and free to post your thinking on any topic. Write on Medium

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store