Ruling Out Fatigue

How did researchers know the Mimosa pudica plants had truly learned, rather than simply tired out? They changed the stimulus. Plants that had stopped folding for the repeated drop still folded instantly when touched by hand or hit by a gust of wind.

That control rules out exhaustion. A worn-out plant would stay limp no matter what. Instead, these plants ignored the one signal they had learned was safe while staying alert to everything else — the mark of a specific memory, not a drained reflex.