Quote:Common sense suggests that there is always room for the brain to expand its activities. Learning to play chess for a simple example. One never feels that one's brain is full and can do no more. We seem to have an endless capacity to learn new things.
Seems to me like this alone is justification enough to carry around the excess capacity.
I'm completely ignorant about the origin of the 10% myth, but from what I have read about the development of the brain I understand that we actually have several times more working circuits in our brain when we are infants than we do by the time we reach adulthood. As we grow up, our brain tries out these circuits, and the ones that get "rewarded" -- that is, the ones that are rewarded by parental attention, or food, or sexual gratification, or whatever -- are reinforced and used again. Those circuits that don't prove to be useful eventually wither and die. It's a common property of what've been termed "complex adaptive systems."
It's probably one of the reasons that children are so adept at learning language, and may account for the discrepancy between potential brain usage and actual brain usage, if such a gap exists. That and fermentable grains...
http://en.wikipedia.org/wiki/Complex_adaptive_system