What Plants Are Saying About Us
I was never into house plants until I bought one on a whim—a prayer plant, it was called, a lush, leafy thing with painterly green spots and ribs of bright red veins. The night I brought it home I heard a rustling in my room. Had something scurried? A mouse? Three jumpy nights passed before I realized what was happening: The plant was moving. During the day, its leaves would splay flat, sunbathing, but at night they’d clamber over one another to stand at attention, their stems steadily rising as the leaves turned vertical, like hands in prayer.
“Who knew plants do stuff?” I marveled. Suddenly plants seemed more interesting. When the pandemic hit, I brought more of them home, just to add some life to the place, and then there were more, and more still, until the ratio of plants to household surfaces bordered on deranged. Bushwhacking through my apartment, I worried whether the plants were getting enough water, or too much water, or the right kind of light—or, in the case of a giant carnivorous pitcher plant hanging from the ceiling, whether I was leaving enough fish food in its traps. But what never occurred to me, not even once, was to wonder what the plants were thinking.
To understand how human minds work, he started with plants.
I was, according to Paco Calvo, guilty of “plant blindness.” Calvo, who runs the Minimal Intelligence Lab at the University of Murcia in Spain where he studies plant behavior, says that to be plant blind is to fail to see plants for what they really are: cognitive organisms endowed with memories, perceptions, and feelings, capable of learning from the past and anticipating the future, able to sense and experience the world.
It’s easy to dismiss such claims because they fly in the face of our leading theory of cognitive science. That theory goes by names like “cognitivism,” “computationalism,” or “representational theory of mind.” It says, in short, the mind is in the head. Cognition boils down to the firings of neurons in our brains.
And plants don’t have brains.
“When I open up a plant, where could intelligence reside?” Calvo says. “That’s framing the problem from the wrong perspective. Maybe that’s not how our intelligence works, either. Maybe it’s not in our heads. If the stuff that plants do deserves the label ‘cognitive,’ then so be it. Let’s rethink our whole theoretical framework.”
Calvo wasn’t into plants, either. Not at first. As a philosopher, he was busy trying to understand human minds. When he began studying cognitive science in the 1990s, the dominant view was the brain was a kind of computer. Just as computers represent data in transistors, which can be in “on” or “off” states corresponding to 0s and 1s, brains were thought to represent data in the states of their neurons, which could be “on” or “off” depending on whether they fire. Computers manipulate their representations according to logical rules, or algorithms, and brains, by analogy, were believed to do the same.