For a long time, people have marveled at the possibility that only 10% of the human brain was actively being used. With everything that humans have accomplished, could it be possible that we have done all of this, far more than any other known species, with only a small portion of our brain power? If somehow the rest of the brain could be tapped, the possibilities would be seemingly endless. Cancer would be a thing of the past, disease in general could quite possible be gone forever, future civilizations would be able to live much more efficiently in general. The myth started far back in the late 1800's by one of the fathers of Psychology, William James. James suggested that most people only fulfill a small portion of their intellectual potential. The myth grew and grew until eventually, it became a quite common misconception.
However, with modern technology, we are much better able to understand the brain and almost literally "see" how it works with neuroimaging. No scientist has yet to discover a silent area of the brain; every area seems to be active at certain times depending on what is needed to perceive our surroundings and actively think, and problem solve. Further modern evidence has helped to debunk the old rumor as well. The fact that many brain damaged people lose the ability to perform a certain function after an injury shows that the damaged area of the brain was vital to that area of operation. This basically means that no matter where in the brain you are injured, consequences will be suffered.... A sad but true fact that destroys any hope of the 10% rumor being true.
Despite the fact that modern science has busted this old myth, I still believe that our brains are "limitless" in some ways. First, people have extraordinary ways of learning and adapting from past mistakes. Every mistake made is a lesson learned, and that makes people smarter every day. We will always learn from the past and continue to evolve as time goes on. I also believe that our potential to learn and discover goes as far as our imagination, which is a long ways. As long as their is the desire to learn more about the world we live in, people will continue to gain knowledge and become smarter, effectively making our brains... limitless.