Can We Talk To Trees? The Surprising Science Behind Plant “Intelligence”
The new Tony Leung drama Silent Friend gives new meaning to the term “tree huggers.”
Are plants conscious?
It’s a question that Silent Friend, Ildikó Enyedi’s mesmerizing and contemplative new drama, ponders in its decades-spanning saga about an old ginkgo tree, and the different generations of people who cross paths with it. One of those people is Dr. Tony Wong (Tony Leung), a neurology professor who encounters the gingko tree at Marburg University, where he becomes unexpectedly quarantined at the start of the 2020 lockdowns. Struck by the gingko tree and its long history at the university, which he finds dates back to 1832, he starts to apply his neurological experiments to it, hoping to prove that plants are conscious.
What he finds: Not only is the gingko tree conscious, it responds to stimuli in a way that hints at a form of communication. But he’s not the first person to make this discovery. As Silent Friend goes on, it flashes back through the years to other people who have attempted human-to-plant communication: first, the first female botany student (Luna Wedler) at Marburg University in 1908, who develops an affinity for the ginkgo tree; then, an awkward loner student (Enzo Brumm) in 1972 who discovers that a purple geranium hooked to a sensor will respond to him. The latter experiment — in which the ‘70s student is actually able to get the geranium to open a gate for him — was based on a newspaper article that director Ildikó Enyedi had read about in the ‘70s, and served as the inspiration for Silent Friend.
“I was a teenager in the '70s, so it was full-speed flower power, world peace, ‘Let's figure out how to live in another way,’” Enyedi tells Inverse. “It was a beautiful time. These experiments were very primitive, very basic. They just put sensors on all sorts of plants, and they were amazed that the plant actually, through electric impulses, shows signs of perceiving the surrounding world.”
In the article that Enyedi read, a Canadian scientist put some sensors on a potted plant in his window. After a while, he figured out how to use the electric signals the plant transmitted to open his garage door. “I found the optimism, the cheerfulness of this experiment fitting for the period,” Enyedi says.
“It's reasonable to talk about plant cognition.”
Of course, this is no formal science research — and potentially apocryphal at that. (Silent Friend’s science consultant, neuroscientist, and scholar on the science of consciousness, Anil Seth, tells me it’s the “first time I've heard of it.”) There are plenty of one-off, wacky experiments out there, like this one in which an American scientist detected electrical spikes in a plant using a polygraph.
But one of real, peer-reviewed science? In 2018, The Overstory drew attention to some of the better studied strange communication patterns between trees — including the communicative properties of mycelial networks.
There’s a surprisingly rich field of research into plant intelligence.
“There are people who call themselves plant neurobiologists,” Seth tells Inverse. “I think it's reasonable to talk about plant cognition. They seem to do things that, if animals did them, we would call them cognitive things like learning, maybe goal-directed behavior.”
The study of plant neurobiology, or plant intelligence, is a fairly recent — and controversial — field of study. Scientists have been studying plant behavior since at least the early 19th century, with various subdisciplines of biology researching whether plants possess intelligence. Some suggest that plants can be studied like animals, applying zoological disciplines, behavioral ecology, or sociobiology to plant life. Others seek to study plants from a strictly biochemical point of view. Still others explore whether plants can display higher cognitive functions like memory or learning. However, much debate has been waged over whether the signals detected in plants actually indicate sentience or if they’re just pure reaction. There’s even debate over whether “intelligence” is the proper terminology; Seth, personally rejects the use of the word “neurobiology” since “trees don’t have brains,” he says.
But still, plants are “much more interesting than people generally give them credit for,” Seth says. “Now, I personally don't think that trees are conscious, certainly not in a comparable way to we are, but I think it's fairly likely there's no subjective experience whatsoever.”
A student in Silent Friend bonds with the ginko tree.
Seth refers to the plot in Silent Friend, in which Leung’s Dr. Tony Wong is turned onto plant neurobiology when he watches a TED Talk by Dr. Alice Sauvage (Léa Seydoux), who argues that plant behavior is more sophisticated than people might think. “There are lots of rich behaviors,” Seth says. “Yeah, they don't have brains, but they do signal [through] Mycelial networks of fungi. Lots of interesting signals pass within and between trees.”
However, Seth stresses that plants are “not comparable to brains.” Seth, whose work is mostly in human consciousness, says the differences are too vast between plants and humans to measure them in comparable ways.
“Lots of interesting signals pass within and between trees.”
“For me, plants are a provocation because they're so dissimilar,” he says. “I think because I'm working from the perspective of science and philosophy, then it's dangerous to generalize too far. We have to go step by step, and I really don't know what it's like to be a bee or an insect or a fish. But these are still animals, they still have brains, they still have neurons so there's a greater degree of similarity there. But being invited to think about trees and plants because we share our lives with these things all the time, I…found it enchanting. And I think that's a thing I feel in mind science and philosophy, too.”
But, ironically, it was Seth’s work that partially inspired Enyedi to make Silent Friend. After meeting him at a roundtable in Cannes a few years ago, she dove into his work, including his book on consciousness and the self, Being You: A New Science of Consciousness.
“What does it mean to be a human? What does it mean to be Tony Leung? What does it mean to be a ginkgo three, standing in a botanical garden for hundreds of years? We kept contact, and he was a very strong inspiration, his research, among many others,” Enyedi says.
Leung’s scientist observes the gingko tree in Silent Friend.
A few other real-life scientists provided inspiration for the movie, including ecologist Monica Gagliano, who specializes in plant bioacoustics (“Our film is called Silent Friend, but actually, they are not silent,” Enyedi jokes), as well as psychology and cognitive science professor Alison Gopnik, who provided the basis for Leung’s character. But Leung himself provided more inspiration for the film than either of them could have anticipated.
“I treat them as sentient beings now, so I never imagined I will see plants in this way.”
“When I asked Tony for this role, I didn't know that he is a serious Buddhist, so it was a beautiful discovery, how these aspects just met each other,” Enyedi says. It results in a movie that has its roots in real-life scientific theory, but takes a more philosophical approach — one that Seth appreciates and approves of. “There's certainly this emphasis on seeing consciousness and mind as part of nature, a continuous with the natural world,” Seth notes. “And that's something that's definitely the view that I've come to over decades of working at the interface of neuroscience and philosophy.”
“During the preparation, the studying of plants really changed my perspective towards plants,” Leung tells Inverse. I didn’t have this kind of experience before. I think the relationship between me and plants are more like human and human. I treat them as sentient beings now, so I never imagined I will see plants in this way.”
The student from 1908 communing with the ginko tree in Silent Friend.
So, are plants conscious? Or more specifically, does Silent Friend portray the science of consciousness in an accurate, or at least, respectful way? Despite his misgivings about the field of plant neurobiology itself, Seth does like what Silent Friend has to say about consciousness as a whole.
“I think we can misunderstand consciousness when we confuse it with other things, whether it's personal identity or intelligence, which is one of the things leading to the over-attribution of consciousness to AI systems now,” Seth says. “And so I think there's this mistake of being overly constrained by the human example. Anthropocentrism, to use a single word. And Silent Friend, I think it's a gentle admonition about that, a gentle pushback.”
