A tree falls in the woods; but whether or not anyone hears it, the tree has no regrets – nor does it experience fear, anger, relief or sadness as it topples to the ground. Trees – and all plants, for that matter – feel nothing at all, because consciousness, emotions and cognition are hallmarks of animals alone, scientists recently reported in an opinion article. The idea that plants have some degree of consciousness first took root in the early 2000s; the term "plant neurobiology" was coined around the notion that some aspects of plant behaviour could be compared to intelligence in animals. Though plants lack brains, the firing of electrical signals in their stems and leaves nonetheless triggered responses that hinted at consciousness, researchers previously reported. But such an idea is nonsense, according to the authors of the new article. Plant biology is complex and fascinating, but it differs so greatly from that of animals that so-called evidence of plants' intelligence is intriguing but inconclusive, the scientists wrote.