Brain myths that won't die
Eight ideas about the brain that feel true, get repeated everywhere, and fall apart the moment you check them against the research.
Some ideas about the brain get repeated so often that almost nobody stops to ask whether they are actually true. They show up in classrooms, self-help books, TED talks, and movie plots until they harden into something that feels like common knowledge. Here are eight of the most stubborn, and what the real research says about each one.
1. “You only use 10 percent of your brain.”
Brain imaging put this one to rest a long time ago. PET and fMRI scans show that over the course of a normal day essentially all of your brain lights up, and there is no idle ninety percent sitting in reserve. Your brain is about two percent of your body weight but burns close to twenty percent of your energy, which is a strange amount to spend on tissue that supposedly does nothing. The psychologist Barry Beyerstein went looking for the source of the ten percent claim and found that it has no real scientific origin at all.
2. “You are either left-brained or right-brained.”
Some functions really do lean to one side. Language usually sits more on the left, and certain kinds of attention lean right. But the pop version, that logical people run on a dominant left hemisphere while artistic people run on a dominant right one, is not how brains work. A University of Utah team led by Jared Nielsen analyzed resting-state scans from more than a thousand people and found no sign that anyone favors one hemisphere as a fixed personal trait. You use both, constantly.
3. “You have one fixed learning style.”
The idea that each of us is a visual, auditory, or kinesthetic learner, and learns best when taught in that one channel, is everywhere in education. The problem is that when researchers test it head on, teaching to a student's supposed style does not improve how much they actually learn. A review led by Harold Pashler for the journal Psychological Science in the Public Interest found almost no credible evidence for it, even after decades of the idea being handed to teachers as settled fact.
4. “Alcohol kills brain cells.”
Drinking really can harm your brain, just not in the tidy way this phrase suggests. When researchers counted the neurons in the brains of people with severe alcoholism and compared them to non-drinkers, they found no drop in the total number of nerve cells. What heavy drinking damages instead is the brain's wiring, the white matter and the connections between cells, along with overall brain volume in the worst cases. Alcohol hurts the brain by degrading its wiring, not by killing off cells one drink at a time.
5. “A bigger brain means a smarter person.”
If size alone decided intelligence, sperm whales and elephants would leave us far behind, and they do not. Among people, brain size and IQ are only loosely linked. A meta-analysis by Jakob Pietschnig and colleagues pooled dozens of studies and found a correlation of about 0.24, which means brain size accounts for only a small slice of the difference in test scores. Neanderthals had larger brains than we do. What matters is how a brain is wired and organized, not how much it weighs.
6. “Humans have five senses.”
The five senses come from Aristotle, and they leave a lot out. You also have proprioception, the sense of where your limbs are without looking, a vestibular sense for balance and acceleration, and separate systems for temperature, pain, and the internal state of your body. The neuroscientist A. D. Craig described that last one, interoception, as a full sensory system in its own right, the way you feel hunger, thirst, or your own heartbeat. Depending on how you count, humans run on somewhere between nine and more than twenty senses. Five was never the real number.
7. “Brain-training games make you smarter.”
Playing them makes you better at the games, and that is roughly where the benefit stops. The largest early test, led by Adrian Owen and run with the BBC across more than eleven thousand people, found that training sharpened the specific tasks people practiced but did not carry over to general memory or reasoning. In 2016 the makers of Lumosity paid two million dollars to settle Federal Trade Commission charges that their ads had promised more than the science could deliver. The gains from brain games tend to stay glued to the exact task you drilled.
8. “The brain is fully developed at 18, or maybe 25.”
The prefrontal cortex, the region behind planning and impulse control, keeps maturing into the mid-twenties, which is where the popular twenty-five figure comes from. But twenty-five is a rough landmark, not a finish line, and nothing snaps into place on a birthday. A 2022 study led by Richard Bethlehem charted more than a hundred thousand brain scans across the whole lifespan and showed that the brain keeps changing the entire way through. Eighteen is far too early to call it finished, and the honest answer is that it never fully stops.
Each one feels true, travels fast, and quietly falls apart the moment you check it against the actual studies.
Why these stick around
Notice what all eight have in common. Each is simple, a little flattering, and easy to pass along, which is exactly what a good myth needs. The real findings are almost always more interesting than the myth they replace, but they take a paragraph instead of a punchline, so the punchline wins.
That gap between the story and the research is the whole reason The Neuroscience Review exists. Every Wednesday it takes one brain-science claim and walks it back to the papers it came from, in plain language, with the sources shown. If this page was useful to you, that is the kind of thing that would land in your inbox. It is free, and you can leave whenever you want.