Why "Left-Brain, Right-Brain" Refuses to Die

Somewhere between a real discovery and a BuzzFeed quiz, “left-brained” and “right-brained” became personality types. Logical, analytical people are supposedly left-brained. Creative, intuitive people are right-brained. It’s a tidy story. It’s also not how brains work.

The real finding underneath the myth

The kernel of truth goes back to Roger Sperry’s split-brain research in the 1960s and 70s, work that later won him a share of the Nobel Prize. Sperry studied patients whose corpus callosum — the thick bundle of fibers connecting the two hemispheres — had been surgically cut to control severe epilepsy. With the two sides of the brain unable to directly share information, Sperry and his collaborators could test each hemisphere in near-isolation, and they found real differences: in most right-handed people, language production leans heavily on the left hemisphere, while certain aspects of spatial attention and face processing lean more on the right.

That’s genuine lateralization. It’s also narrow, task-specific, and a long way from “creative people use their right hemisphere more.”

What a thousand brains actually showed

In 2013, a team at the University of Utah led by Jared Nielsen tested the pop-psychology version directly. Using resting-state fMRI data from over a thousand people, they looked for evidence that some individuals consistently favor whole-hemisphere “left-brain” or “right-brain” processing. They found specific regions that were more left- or right-lateralized on average, exactly as Sperry’s work would predict — but no sign that any person’s brain, as a whole, leaned reliably to one side more than another’s. Analytical and creative thinking both draw on networks that span both hemispheres, working together via the very corpus callosum that Sperry’s patients had lost.

Why the myth survives anyway

A few reasons it keeps coming back:

It’s an intuitive dichotomy. Two categories, two brain halves — the story maps itself onto the anatomy in a way that feels self-evidently true.
It’s commercially useful. Personality quizzes, brain-training apps, and self-help books all benefit from a simple typology people can identify with.
The underlying science is real, which lends it credibility. Lateralization does exist. The myth borrows its authority from Sperry’s genuine, Nobel-winning work, then generalizes it far past what that work showed.

What’s actually true

Specific functions do lateralize, and reliably so — language production being the clearest example. But an intact brain uses both hemispheres constantly and in close coordination for almost everything people care about, including the things “right-brain” marketing claims as its own: creativity, in particular, shows up in imaging studies as a distributed, whole-brain process, not a right-hemisphere specialty.

If you want a one-line replacement for the myth: your brain isn’t one type or the other. It’s cooperating with itself, all the time, through several hundred million fibers built for exactly that.

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