Maybe Plants Remember Stuff

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Photo: Che Che

Plants are like quiet, charming aliens: refreshing of air, looking good in green, living at a much chiller timescale than the energetic inhabitants of the animal kingdom. In a post at the Brain Blog, Dickinson College philosopher Chauncey Maher advances the argument that some plants, at least, seem to partake one of the most fundamental of human pastimes: remembering.

Case in point: the beloved and feared Venus flytrap. It only snaps shut when two of its whiskery little hairs have been touched, one within 20 seconds of the other. (This, the hypothesis goes, is so that it may only nom upon flies and other deliciousness, rather than some leaf falling from above.) Maher references a biologist and cognitive scientists, leading proponents of the idea that “it seems the Venus flytrap remembers that one hair has recently been touched,” and that memory(-like) process triggers action.

That’s not all: Root growth may involve a kind of remembering, too. If a root is going downward and hits something, it’ll go sideways, and if it’s impeded again, it’ll return to its downward trajectory. Similarly, phototorsion — or how leaves orient themselves to the sun, tracking it through the day — reminds one of memory. “[T]he memory-like thing, is that overnight, they turn back to where the sun will be in the morning! They seem to encode, store, and retrieve that information,” Maher writes.

What’s difficult here, he says, is that these behaviors don’t fit neatly into the models of memory that psychologists usually hold: episodic, or those little movie scenes you recall in your mind; procedural, or learning motor skills and the like; and semantic, or the recall of facts and things that you haven’t experienced firsthand, like the capital of Maryland (Annapolis) or weird blog posts about plant intelligence (this one). So if this is a kind of remembering, it’s more modest than those, and belonging to what the plant-intelligence advocates call “minimal cognition.”

One may also raise the reasonable objection that plants don’t have brains. However, some very convincing philosophers would argue otherwise: as far as we know, lots of animals do stuff without being consciously, metacognitively aware that they’re doing it. “What we learned from Darwin is that competence precedes comprehension,” Tufts professor Dan Dennett, who’s something of a celebrity in the philosophy game, told Michael Pollan and The New Yorker in a 2013 feature on plant intelligence. “The idea that there is a bright line, with real comprehension and real minds on the far side of the chasm, and animals or plants on the other — that’s an archaic myth,” he said, and to think that memory means nothing in the absence of brains is — and here’s a high-quality neologism — “cerebrocentric.” And you don’t want to be cerebrocentric, do you?

Maybe Plants Remember Stuff