Tuesday, January 14, 2014

Some Limited Notes on Plant Cognition

So today I'm going to ramble on a bit about some of the possibilities of plant cognition- if you could call it that, as plants do not have brains. The fact that plants cannot think or do not have consciousness is widely believed, but in fact that is hard to prove because the lack of widely accepted operational definitions of thought/consciousness. What exactly are they? Are they processes that can only exist in a brain? Only in a human brain?

Unfortunately, that is how it seems to be defined presently. Most of the scientific studies being done on consciousness involve the respondent giving verbal answers to indicate their experience with stimulus, which is not the most rigorous data collection  method. In addition, only people can provide verbal answers, and so skews the proof of consciousness to humans alone. Some methods have used EEG and fMRIs for studies, but again, without a widely accepted operational of consciousness, it is difficult to find evidence of consciousness. This is especially difficult when talking about plants, because the measures of consciousness/cognition currently used require a brain or some verbal capacity, and plants have neither.

However, plants do exhibit some behaviors we find associated with cognition, despite not having a brain. One example is dubbed the "wood wide web." Plants nearby each other will oftentimes connect at the roots, allowing them to exchange nutrients and information. Scientists have found that during winter months evergreens will provide nutrients to deciduous trees. This is not just pro bonum, though, as the debt is repaid during the summer months when the deciduous trees tend to block light from the evergreens. Fungi, though not plants, also exhibit similar behavior, and there are studies showing that they have a level of self-recognition, which is often a prerequisite for consciousness (hence the mirror test used on animals- but that won't work on plants because of the lack of eyes, and there are some issues with the validity of the mirror test). The exchanging of information and settling of scores, while not prove of cognition, certainly seem to point in that general direction.

In addition, some plants have memory, something also indicative, though not proof, of thought. Mimosa pudica plants close their leaves when disturbed as a defense mechanism. Researchers found that when they dropped the plants from a height repeatedly they learned that the fall was not a threat and stopped closing. They responded, however, to shaking and other threats regularly. For several months the plants would not react to a fall, showing a memory of the stimulus. So, lacking what many consider necessary for memory storage (brain or at least a centralized neural system), they store memory anyway. This opens the possibility of other cognitive behavior in plants, even without brains.
The plant, not the drink

Of course, this is far from being proven and highly speculative, but it shows that plants need more credit than we give them.

On a side not, plants can also hear! I'm attaching the video that inspired this post, and also provided much of the information, which explains more about plant auditory and other senses.

Also, in my research I also learned about the philosophical zombie! Unfortunately its not a Descartes spouting undead being, but a thought experiment to critique the methods of measuring consciousness. It is a theoretical being who could respond as if they experienced stimuli when in fact that they had not, thus mimicking consciousness but not experiencing consciousness.

Explained by Dinosaur Comics

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