The remarkable ability of plants to respond to their environment has led some scientists to believe it’s a sign of conscious awareness. A new opinion paper argues against this position, saying plants “neither possess nor require consciousness.”
Many of us take it for granted that plants, which lack a brain or central nervous system, wouldn’t have the capacity for conscious awareness. That’s not to suggest, however, that plants don’t exhibit intelligence. Plants seem to demonstrate a startling array of abilities, such as computation, communication, recognizing overcrowding, and mobilizing defenses, among other clever vegetative tricks.
To explain these apparent behaviors, a subset of scientists known as plant neurobiologists has argued that plants possess a form of consciousness. Most notably, evolutionary ecologist Monica Gagliano has performed experiments that allegedly hint at capacities such as habituation (learning from experience) and classical conditioning (like Pavlov’s salivating dogs). In these experiments, plants apparently “learned” to stop curling their leaves after being dropped repeatedly or to spread their leaves in anticipation of a light source. Armed with this experimental evidence, Gagliano and others have claimed, quite controversially, that because plants can learn and exhibit other forms of intelligence, they must be conscious.
Nonsense, argues a new paper published today in Trends in Plant Science. The lead author of the new paper, biologist Lincoln Taiz from the University of California at Santa Cruz, isn’t denying plant intelligence, but makes a strong case against their being conscious.