Do We Really Only Use Only 10% of our Brains?
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Do We Really Only Use Only 10% of our Brains?
“I flunked my math test. But it’s not my fault, it’s genetic! Humans only use 10% of their brains, right? If I could get to full capacity, I’d be a genius!” Wrong. Why? Let’s find out. We’ll be debunking this ‘we-only-use-10-percent-of-our-brain’ myth in this segment.
Welcome to Isthmus, the auditory content for the University of Wisconsin-Madison’s Journal for Undergraduate Science and Technology. I’m Shriya Kulkarni, a writer with JUST and a BME student. I love research, and I love proving people wrong, so strap in to do both!
Origins
The origins of the we-only-use-10-percent-of-our-brain myth—which will be referred to as the ‘10% myth’ from here—are unclear, though there are several possible sources. In his 1907 book Energies of Men, William James, an influential psychologist and author at the time, argued that humans only use a part of their mental resources, though he did not specify a percentage. The myth was also mentioned in How to Win Friends and Influence People, a 1936 book by Dale Carnegie, as something his college professor used to say. It has been widely repeated in articles, TV programs, and films as well, which may account for its widespread popularity. We even use it to mask our shortcomings— saying ‘I have tons of potential. It’s just untapped’ sounds so much better than ‘I can’t do this,’ don’t you think? On a slightly more scientific note, scientists at the time believed that neurons made up around 10% of the brain’s cells (Boyd, 2008). Neurons are cells in the nervous system that transmit electrical impulses around the body (National Institute of Neurological Disorders and Stroke, 2025). The other 90% was believed to be made up of glial cells, which enclosed and supported neurons, but their function remained largely unknown. In other words, we only understood the workings of 10% of our brain. This may have contributed to the 10% myth as well. However, now we not only know the function of glia, which is to provide support and protection to neurons, but also that they are roughly equal in number to neurons (Allen & Lyons, 2018).
Debunking
While the 10% myth may sound logical at first, it can be proven incorrect using a mixture of logic and related scientific discoveries. One of the first people to put forward arguments disproving this myth was neuroscientist Barry Beyerstein. His arguments boil down to the points which I’ll be talking about from here. If we only normally use 10% of the brain, then damage to one part of the brain should hypothetically not impair performance in all fields. But in reality, there is almost no area of the brain that can be damaged without facing a loss of abilities tied to that area. In fact, minor damage to any part of the brain can cause complex effects (Mayo Clinic, 2021). Plus, brain scans have proven that no matter what a person is doing, multiple areas of the brain are always active. Some areas may be more active than others, but barring brain damage, there are no areas that are fully inactive (Rule et al., 2020). Another reason that this myth is… well, just that, is rooted in human evolution. The brain is metabolically expensive: it is responsible for a great deal of the body’s oxygen and nutrient consumption (Kuzawa et al., 2014). If 90% of the brain were redundant, then having small brains (and further, small heads) would be an immense survival advantage in the sense that less energy would be wasted in maintaining an organ that does not need it. And finally, there exists a phase in the development of the nervous system called synaptic pruning, which is the ability of the brain to cause unused brain cells to degenerate (Sakai, 2020). So if 90% of the brain were unused and inactive, then an autopsy of adult brains would show large-scale degeneration (Beyerstein, 2004). On the other end of the spectrum, 100% brain usage isn’t desirable either. Too many neurons firing at the same time could lead to an epileptic seizure (National Institute of Neurological Disorders and Stroke, 2025b). However, even at rest, a person likely uses as much of their brain as reasonably possible through the default mode network, a widespread brain network that is active and synchronized even in the absence of any cognitive task (Menon, 2023). This is why large portions of the brain are never truly dormant, as opposed to what the 10% myth claims.
Conclusion
So to conclude, we do not use only 10% of our brain. We use almost all of it at all times, even when we’re sleeping. Our brain can do as much as we train it to, or like author Emily Dickinson said, “The brain is wider than the sky” (Thompson, 2015).
I hope you enjoyed this segment on neurological myth-busting! To finish off, I’d like to thank JUST’s sponsors: the Associated Students of Madison, College of Agriculture and Life Science, Wisconsin Institute of Discovery, Wisconsin Alumni Research Foundation, Dr. Todd Newman, and Dr. Joan Jorgenson. Thank you for listening– be sure to find our printed journals across the UW-Madison campus at the end of the semester! This has been Shriya Kulkarni, with another segment of Isthmus.
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References:
Allen, N. J., & Lyons, D. A. (2018). Glia as architects of central nervous system formation and function. Science,362(6411), 181–185. https://doi.org/10.1126/science.aat0473
Beyerstein, B. L. (2004, March 8). Do we really use only 10 percent of our brains? Scientific American. https://www.scientificamerican.com/article/do-we-really-use-only-10/
Boyd, R. (2008, February 7). Do People Only Use 10 Percent of Their Brains? Scientific American. https://www.scientificamerican.com/article/do-people-only-use-10-percent-of-their-brains/
Carnegie, D. (1936). How to Win Friends and Influence People. Simon & Schuster.
James, W. (1907). The Energies of Men. Moffat, Yard & Company.
Kuzawa, C. W., Chugani, H. T., Grossman, L. I., Lipovich, L., Muzik, O., Hof, P. R., Wildman, D. E., Sherwood, C. C., Leonard, W. R., & Lange, N. (2014). Metabolic costs and evolutionary implications of human brain development. Proceedings of the National Academy of Sciences, 111(36), 13010–13015. https://doi.org/10.1073/pnas.1323099111
Mayo Clinic. (2021, February 4). Traumatic brain injury - symptoms and causes. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/traumatic-brain-injury/symptoms-causes/syc-20378557
Menon, V. (2023). 20 years of the default mode network: A review and synthesis. Neuron, 111(16). https://doi.org/10.1016/j.neuron.2023.04.023
National Institute of Neurological Disorders and Stroke. (2025a, February 25). Brain basics: The life and death of a neuron. https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-life-and-death-neuron
National Institute of Neurological Disorders and Stroke. (2025b, April 7). Epilepsy and seizures. https://www.ninds.nih.gov/health-information/disorders/epilepsy-and-seizures
Rule, M. E., Loback, A. R., Raman, D. V., Driscoll, L. N., Harvey, C. D., & O’Leary, T. (2020). Stable task information from an unstable neural population. eLife, 9. https://doi.org/10.7554/elife.51121
Sakai, J. (2020). Core concept: How synaptic pruning shapes neural wiring during development and, possibly, in disease. Proceedings of the National Academy of Sciences, 117(28), 16096–16099. https://doi.org/10.1073/pnas.2010281117
Thompson, E. (2015). The Brain Is Wider Than the Sky: What Emily Dickenson Can Teach Neuroscience. Psychology Today. https://www.psychologytoday.com/us/blog/waking-dreaming-being/201504/the-brain-is-wider-the-sky
