Expert: John Locke - 10/29/2007

Question
Hi, do you know where consciousness arises in the animal kingdom following evolution? Why is it that only animals possess a consciousness that allows them to act on purpose, to feel pain and pleasure and why don't plants have the apparatus to feel all this? Thanks.

Answer
Thanks for using AllExperts, Jack. This question is a bit beyond my expertise, but I can suggest some general answers to your question, and perhaps some areas of further study that will help you find an answer. In short, the basic requirement for consciousness to exist is some kind of neural network. A brain is a type of neural network (though there can be other types), in which neurons (nerve cells) interconnect with each other and can send messages back and forth. More complex brains allow for more complex interaction with the world, but that doesn't necessarily mean that a more complex brain leads to more consciousness: human brains are more complex than rat brains, obviously, and humans have a more sophisticated understanding of their surroundings. That doesn't answer this question, however: is a rat less conscious than a human?

Meditating on this leads to other, related questions: Is a monkey more conscious than a cat? Can an artificial neural network generate consciousness in a machine? As you can see, the problem starts with the definition--what is to be considered consciousness?--and only expands from there. Any books that you might wish to read on the subject will start  by trying to define it because it's so problematic. A number of sources seem to indicate that certain parts of the brain are particularly important for the existence of consciousness, like the prefontal cortex--you may wish to research that further. Why did consciousness evolve in the first place? That's a question I certainly can't answer, but I can tell you that many biologists regard consciousness as a valuable adaptation: organisms that have some form of conscious awareness are much better at surviving than those without it. That suggests why it has been maintained in animals, though not how it arose in the first place.

Plants don't have a complex neural network, and thus are generally not considered to have consciousness, though they can respond to their environment in a coordinated way. Plants, for instance, can move toward sources of sunlight and away from shadow, though (so far as we can tell) there is no consciousness involved in this process, just a collection of individual responses.

I am sorry that I can't answer your question directly, but I wish you the best of luck.