Where did the notion that we use only 10% of our brains come from? On what basis is this claim made?

Not true, @talljasperman. It came from pretty much nowhere, and goes as far back as the 1920s (There’s an advertisement for the 1929 World Almanac containing the line “There is NO LIMIT to what the human brain can accomplish. Scientists and psychologists tell us we use only about TEN PER CENT of our brain power.” From wikipedia). MRI scans show no such thing (they generally show the majority of our brain is active, to different degrees depending on the task). The most plausible explanation for the origin is that it was taking the idea of “people don’t live up to their potential” and attaching a number to it to make it sound sciency. It was pulled out of someone’s nether regions and now refuses to die.

^^^What he said (pretty much what I was about to write).

Q: Where did the notion that we use only 10% of our brains come from? On what basis is this claim made?

A: They studied Republicans.

Seriously, 10% is a joke. When the claim was initially made, they had no way to measure that. They still can’t.

By observing the way the public operates their motor vehicles.

Ask Lucy, she knows.

Evolutionarily, the idea that we use only a small portion of our brain is laughably fallacious. Brains are expensive to grow and maintain; it would make absolutely no sense for us to have such a large organ if it were not fully functional.

Here’s a whole bunch of sites that refer to the myth as debunked.

As to the origin, there’s this:

One possible origin is the reserve energy theories by Harvard psychologists William James and Boris Sidis in the 1890s who tested the theory in the accelerated raising of child prodigy William Sidis to effect an adulthood IQ of 250–300; thus, William James told audiences that people only meet a fraction of their full mental potential, which is a plausible claim.[5] In 1936, American writer Lowell Thomas summarized this idea (in a foreword to Dale Carnegie’s How to Win Friends and Influence People) by adding a falsely precise percentage: “Professor William James of Harvard used to say that the average man develops only ten percent of his latent mental ability.”[6] However, this book was not the first to use the 10% figure, which was already circulating within the self-help movement before then; for example, the book Mind Myths: Exploring Popular Assumptions About the Mind and Brain includes a chapter on the 10% myth which shows a self-help advertisement from the 1929 World Almanac containing the line “There is NO LIMIT to what the human brain can accomplish. Scientists and psychologists tell us we use only about TEN PER CENT of our brain power.”

In the 1970s, psychologist and educator Georgi Lozanov, proposed the teaching method of suggestopedia believing “that we might be using only five to ten percent of our mental capacity.”[8][9] The origin of the myth has also been attributed to Dr. Wilder Penfield, the U.S.-born neurosurgeon who was the first director of Montreal Neurological Institute of McGill University.

According to a related origin story, the 10% myth most likely arose from a misunderstanding (or misrepresentation) of neurological research in the late 19th century or early 20th century. For example, the functions of many brain regions (especially in the cerebral cortex) are complex enough that the effects of damage are subtle, leading early neurologists to wonder what these regions did.[11] The brain was also discovered to consist mostly of glial cells, which seemed to have very minor functions. Dr. James W. Kalat, author of the textbook Biological Psychology, points out that neuroscientists in the 1930s knew about the large number of “local” neurons in the brain. The misunderstanding of the function of local neurons may have led to the 10% myth.[12] The myth might have been propagated simply by a truncation of the idea that some use a small percentage of their brains at any given time.

Source

I suspect the original idea was that we only get to use about 10% of the organ’s potential in an average life. Where, in theory, we could survive about 10 times as much intake into our brains but we just never get around to filling it all the way up.

Maybe the 10%, or even 25%, figure is way low, so this idea has the trappings of a myth. Maybe we actually use more.
Yet, we’ve all heard tales of individuals who are capable of accomplishing incredible mental feats. I can’t help thinking that maybe we all have untapped potential that we are just unable to access. We cannot unlock it for some reason. And think of great minds like Einstein, Hawkins, etc. They seem to have had extra brain power. Was their biology such that they were able to use this extra potential while we can’t?

I agree, that %10 seems very low, and obviously there have been proven points of it being a myth. . . BUT I still believe that we are not using our brains to our full potential.
We’ve become a lazy society, and I thik it shows, but when someone accomplishes something great it makes you think about all of the things others could be doing too.

But yeah, the 10% thing is silly.