Popular Myth: "We Only Use 10% Of Our Brain Capacity"

One of the most popular myth in science history is a statement that we only utilize 10% of our brain capacity. This myth makes most people to believe that there are 90% more capabilities that are still waited to be used. Just to mention a few, telepathy, super-human regeneration or even x-ray vision.

Even though this myth is often attributed to William James (the father of Americam psychology) and Albert Einstein, it's still unclear how this all begin. However, public were already aware of this myth in late 1930s. And just like many other pseudoscience, some authorative figures also helped the spread of this false information. During 1950s, this misleading informarion was widely (and wildly) used in many self improvement industries, even in some Dale Carnegie's works..!

10% brain capacity might be true if we're talking about Homer
Simpson who lives in The Simpson Universe

It could be very possible that this myth is triggered by misinterpretation on neurological studies conducted in 1930s. At that time, it was well-known that there are many researchers used electrical stimulation to figure out corelation between physical functions and brain cortex. When a certain area of animals' cortex is stimulated, a physical response will occur. This phenomenon also happens on human. However, there are wide area of brain cortex that don't induce physical/motoric reaction. At that time, researchers call those area as silent cortex, which possibly misinterpreted by the myth starter(s) as part of brain that are left unused or still not activated.

The Facts

There were neither neurologist nor researchers who interpret the phenomenon as what those myth starters thought. In fact, the silent cortex hold function for other important things rather than motoric response; such as linguistic, logical processing, and perceptions. With the current technology advancement, this 10 % myth is easily debunked. Modern brain imaging shows that every part of brain is continuously active. Certain tasks increase activity levels in particular brain area, but even we are sleeping there is no part of our brain that is inactive; unless the brain sufferring tissue damage.

The most simple yet way to counter this myth is what we can get from observing stroke or alzheimer victims, where small damage happened on small areas of the brain, yet giving a disastrous impact. Stroke victims lost about 1% of their total brain mass, while Alzheimer victims experience 10-20% cortex damage, which then lead to a complete memory and/or senses loss.

Regardless of the facts, this 10% myth is still firmly believed by the Transcendental Meditation moevement and Scientology. So, unless you are part of those beliefs, please stop saying that our brain only use 10% of its capacity.

Further Reading: 
Beyerstein, B. L. “Whence Cometh the Myth That We Only Use 10% of Our Brains?” In S. Della Sala, ed. Mind Myths: Exploring Popular Assumptions about the Mind and Brain. New York: Wiley, 1999, pp. 3–24.