Around 1800 the French botanist René Desfontaines took a potted mimosa for a ride through Paris in a horse-drawn carriage. Mimosa pudica folds its leaves shut at the slightest touch, and when the carriage started jolting it closed up as expected. Then, as the ride went on, it opened again and stayed open, bumping along like a passenger who has decided the road is just the road. He mentioned it briefly in a book about French trees and shrubs, and that was that for about two hundred years.

In 2014 the ecologist Monica Gagliano did the experiment properly. She dropped potted mimosas about fifteen centimetres, sixty times in a row, and by the end most had stopped folding. They weren’t tired: shake one sideways instead and it shut at once. They had sorted the fall into the category of things that happen and don’t matter. Tested again twenty-eight days later, they still knew.

A plant has no neurons, so wherever it keeps that, it isn’t where we keep ours. What I like is the shape of the lesson it learned, which is the hard one: not “this is dangerous” but “this, specifically, is not”. Most of growing up is learning which of the jolts to stop flinching at.