DEBUNKED: Do We Really Only Use 10% of Our Brains?

“You only use 10% of your brain.” We've all heard this claim; it's one of those stubborn myths that just won't go away. It sounds exciting, doesn't it? Imagine unlocking hidden mental powers or genius-level intelligence just by tapping into that unused potential like in sci-fi movies. However, this claim is completely false. Let's break down where this idea came from, debunk it, and explain what your brain is really up to when you're using it.

The Origins

This myth started in the 1800s by the psychologist William James. He suggested people only show a small part of their mental abilities, but it was just a thought, not actual science.(1) In the 1930s, self-help writers twisted this thought into the “10% of your brain” claim to sell books and courses.(2) Later, movies like Limitless and Lucy furthered this myth by showing characters becoming superhuman by “unlocking” their brains. Although it can make for great stories and movies, those miracle brain drugs would land you in the hospital, not turn you into a genius in real life.(3) Why does the myth stick around? It’s comforting to think our struggles come from unused potential—not the harder truth that learning takes work and brains have limits.

Why the Myth Is Biologically Impossible

Your Brain Is Already Running at Full Capacity

MRI and fMRI scans show no region of the brain is completely inactive.

fMRI and PET scans show that no region of the brain is completely inactive; even simple tasks like watching TV or daydreaming engage multiple areas. The default mode network (DMN), a set of interconnected brain regions, becomes highly active when you’re not focusing on a task, which demonstrates that “idle” time is still neurologically productive.⁽⁴⁾ We can think of our brain like a smartphone, where even if we’re not currently using an app, there is still activity occurring in the background. Brain damage disproves the myth since injuries to those areas wouldn’t matter if 90% of the brain were unused. However, even small lesions can cause devastating deficits in speech, memory, or movement.⁽⁵⁾

Evolution Doesn’t Waste Energy

Over the course of evolution, natural selection would have eliminated such inefficiency millennia ago.

The brain is an energy hog. Despite it only being 2% of our body’s weight, it consumes 20% of our oxygen and glucose.⁽⁶⁾ If 90% were truly dormant, natural selection would have eliminated such inefficiency millennia ago.

Neuroplasticity ≠ Hidden Potential

London taxi drivers develop enlarged hippocampi because of an increased need for spatial memory.

Yes, your brain rewires itself when you learn, but that’s optimizing existing circuits, not “activating” unused tissue. For example, musicians have functional and structural changes in areas responsible for motor control and auditory processing compared to non-musicians due to exposure to music.⁽⁷⁾ Also, London taxi drivers develop enlarged hippocampi due to spatial memory demands, but this comes at the cost of other cognitive functions.⁽⁸⁾ Additionally, blind individuals repurpose visual cortex areas for enhanced hearing or touch—not because those regions were “unused,” but because the brain adapts to loss.⁽⁹⁾

Why the Myth Is Harmful (Beyond Just Being Wrong)

People may get tricked into buying "brain-boosting" pills or mental training programs that promise quick thinking.

This myth being spread has a variety of consequences. For starters, it tricks people into wasting money on fake “brain-boosting” pills and sketchy mental training programs that promise quick fixes. Worse, it makes people think that if they struggle to learn or focus, it’s because they’re not “using enough” of their brain—when in reality, brains just work differently, and that’s normal. Instead of chasing this myth, we should focus on what neuroscience actually tells us—like how brain cells communicate, how gut health affects thinking, and why sleep matters so much for memory. The truth about the brain is far more interesting than some made-up percentage.(10)

Sources

1. James, W. (1907). The Energies of Men. Science.

2. Beyerstein, B. L. (1999). The Myth of 10% Brain Use. Skeptical Inquirer.

3. Racine et al. (2005). fMRI in the Public Eye. Nature Reviews Neuroscience.

4. Raichle, M. E. (2015). The Brain’s Default Mode Network. Annual Review of Neuroscience.

5. Kolb & Whishaw (2009). Fundamentals of Human Neuropsychology.

6. Herculano-Houzel, S. (2016). The Human Advantage. MIT Press.

7. Olszewska et al. (2021). How Musical Training Shapes the Adult Brain: Predispositions and Neuroplasticity

8. Maguire et al. (2000). Navigation-Related Structural Change in Taxi Drivers’ Brains. PNAS.

9. Pascual-Leone et al. (2005). The Plastic Human Brain Cortex. Annual Review of Neuroscience.

10. Mayer et al. (2014). Gut Microbiota and Brain Function. Nature Reviews Neuroscience.