You’ve probably seen those online tests that ask, “Are you right-brained or left-brained?” If you’re creative, the right side supposedly leads. If you’re logical, the left side does. It sounds neat, and it puts you into a tidy little box. But when you ask science, the answer surprises most people: you use both, almost all the time. Let’s unpack where this idea came from, why it spread so widely, and what the reality is. We’ll also take a quick look at the surprisingly connected history of IQ.
Where did the idea come from? A surprising operating-room discovery
The story goes back to the 1800s. French physician Paul Broca, and later German neurologist Carl Wernicke, found that language is processed largely in the left half of the brain. That’s when the idea first took shape that “the two halves are not equal; some jobs are concentrated on one side.”
The truly striking findings came in the 1960s. As a last resort for severe epilepsy, brain surgeons cut the thick bundle of fibers linking the two hemispheres — the corpus callosum. In experiments with these “split-brain” patients, Roger Sperry and his student Michael Gazzaniga saw something remarkable: the two hemispheres could work independently, almost like two separate minds. The left side seemed stronger in language, logic, and sequential processing, while the right side appeared better at spatial perception, face recognition, and holistic vision. The discovery was so important that Sperry received the Nobel Prize in 1981.
How did a scientific finding turn into a myth?
That’s where things went off the rails. What scientists were actually saying was measured: “Some functions are a bit more concentrated in one hemisphere.” But popular culture turned that nuanced finding into something very different. In the 1970s, the topic spread through publications ranging from Time to Harvard Business Review; in 1976, even an article titled “Plan with the Left, Manage with the Right” appeared. A personality template was born: left-brained people are logical and analytical, right-brained people are creative and emotional.
With the added weight of the Nobel Prize, the idea spread fast. Personality tests, apps that claimed to “strengthen the weak half,” and education methods built around “whole-brain learning” all rested on this simple but wrong template. The truth was too rich to fit into a slogan.
Modern neuroscience has debunked the myth
In 2013, a research team imaged the brains of more than 1,000 people and asked a simple question: do “left-brain dominant” or “right-brain dominant” people really exist? The answer was clear: no. There was no evidence that people use one hemisphere more heavily than the other in that way. In healthy brains, both hemispheres worked at roughly the same level.
So what is true? Some functions really are more tied to one side. Language, for example, is mostly on the left for most people. Spatial thinking and face recognition lean a bit more to the right. But that is not a personality type; it is just task distribution. And thanks to the corpus callosum bridge, the two halves are constantly talking to each other. In almost everything you do, both are involved. You use your whole brain when you draw a picture, and you use your whole brain when you solve a math problem.
In short, the line “creative people use the right brain, logical people use the left brain” is a nice-sounding but misleading simplification.
This story is very similar to the story of measuring intelligence
What’s interesting is that the human mind has long wanted to squeeze itself into a single label. We see the same habit in the history of measuring intelligence. The question “Which brain do I use?” is as appealing as “What’s my IQ score, and which box do I fit in?” And the answer to both is more layered than it looks.
A short and surprising history of IQ
The idea of expressing intelligence as a number is actually quite new. Here’s a quick timeline:
| Year | Who | What happened? |
|---|---|---|
| 1905 | Binet & Simon (France) | The first usable intelligence test; the goal was to identify children struggling at school and help them |
| 1912 | William Stern | The term “IQ”: mental age ÷ chronological age × 100 |
| 1916 | Lewis Terman (Stanford) | The Stanford-Binet test; it made IQ mainstream in the United States |
| 1917 | U.S. Army | The first large-scale test, given to more than 1 million soldiers during World War I |
| 1939 | David Wechsler | “Deviation IQ”: average 100, a modern approach that measures different abilities separately |
| 1980s | James Flynn | Showed that IQ scores rose across generations (the Flynn effect) |
Here’s a little-known but striking detail: Alfred Binet, the inventor of the test, openly opposed using his tool to label a child permanently. In his view, intelligence was not fixed; it could be developed. The test was only meant to find the children who needed help. Ironically, many of the people who later used the test ignored that warning.
The Flynn effect points to the same lesson: if intelligence were completely fixed and inborn, scores could not rise across generations. That means education, nutrition, and environment are part of the picture — so the mind is, at least to some degree, something that can change.
The shared lesson: you can’t fit the brain or intelligence into one box
The right-brain/left-brain myth and the idea that “IQ = a fixed stamp” make the same mistake: they reduce something rich and flexible to a single simple label. In reality, the brain works as a whole, and intelligence is much more than one number — logic, memory, creativity, intuition, emotional skills... all of it works together.
The honest answer to “Which brain do I use?” is: both, all the time. Maybe a better question is: Am I keeping my whole mind active and curious?
So what should you do?
The good news is that training your mind in different ways is simple and enjoyable. Puzzles that tap different skills, plus memory and logic games, get different parts of the brain working together. If you want to start, you can try our free brain games without signing up; word, math, memory, and logic games give you exactly that variety. And if you’re curious about your own mental snapshot, you can take a look at our IQ test — but remember, as Binet said, it’s not a label, just a starting point.
In the end, you are not a “right-brain” or “left-brain” person. You’re a person using a whole brain, all of it. And as long as you keep it curious, it stays open to growth.