This idea seems to go back to somewhere at the beginning of the 20th Century. While different people are attributed to having said this, it is not even really clear where this comes from, but I know where it is going! Measuring the brain's activity has been done through a wide variety of different tests, from EEG (i.e.: brain wave activity as measure by electrical impulses) to fMRI (i.e.:taking pictures of hydrogen molecules resonating in the brain). fMRI allows researchers to take snap shot pictures of the brain and its activities in particular locations in the brain, and from this research it was found that all of the brain is being used. There was not one area that did not "light up". That strongly suggests that we are using all of our brain.
The brain in relation to the entire body is quite a small organ, accounting for only 2% of the total weight. Yet, at the same time, the brain requires 20% of the blood flow of the heart and an equal amount of available oxygen. From an evolutionary point of view, is it really plausible that such a demanding organ would only work at 10% of its capacity?
Many times it is said that if one area of the brain is damaged, another part of the brain can take over its function. Surely, this must mean that there are spare parts lying around, waiting to jump into action. Well, no! This just bears witness to the brains amazing ability to rewire itself, also known as neuroplasticity. This plasticity of the brain is very high in children, and although greatly diminished, still available to adults as well in degrees we thought impossible. The brain actually bears evidence to all our decisions in its very structure...
So, now comes the point where most people say:"Wait a minute, its not 10% of the brain, it is 10% of the mind!" My question is, how do you know? How can we even claim to measure the mind and the human potential? Hence, we leave the area of scientific claims, and end up in an almost philosophical discussion that is blurred by injecting scientifically sounding claims with percentages attached to them.
I believe (sic!) that we do have untapped potential, yet not in the form proponents of the 10% myth mean. I think it is not really how much of our mind we use, but how we use it. It is not about getting more (the everlasting vicious cycle of economy), but rather learning to use what we have in as many ways as possible. The more creative we are in using what we have, the more choices suddenly open up right in front of our own eyes. So don't aspire for more, aspire for creativity in using what is already there and that will give you all the "more" you can ever need!