Credit: Miguel Rio Branco
A few years ago, Monica Gagliano, an associate professor in evolutionary ecology at the University of Western Australia, began dropping potted Mimosa pudicas. She used a sliding steel rail that guided them to six inches above a cushioned surface, then let them fall. The plant, which is leafy and green with pink-purple flower heads, is commonly known as a “shameplant” or a “touch-me-not” because its leaves fold inward when it’s disturbed. In theory, it would defend itself against any attack, indiscriminately perceiving any touch or drop as an offense and closing itself up.
The first time Gagliano dropped the plants—fifty-six of them—from the measured height, they responded as expected. But after several more drops, fewer of them closed. She dropped each of them sixty times, in five-second intervals. Eventually, all of them stopped closing. She continued like this for twenty-eight days, but none of them ever closed up again. It was only when she bothered them differently—such as by grabbing them—that they reverted to their usual defense mechanism.
