What the split-brain experiments really showed, which functions are lateralised, and why the 'left-brained versus right-brained' personality idea is a myth.
Brain Anatomy
Beginner
Left Brain, Right Brain and the Corpus Callosum
The Editors
August 25, 2026
3 min read
In plain English
Your brain has two halves joined by a thick bundle of fibres, the corpus callosum. Each half specialises a little — language is usually on the left — but they work together all the time. When surgeons cut the connection, the two halves can act surprisingly independently.
Beginner level: No background needed. Everyday language, everyday examples — the place to start.
Concepts to know first
Go deeper next
The cerebrum is divided into left and right hemispheres, each controlling and sensing mainly the opposite side of the body. They are linked by the corpus callosum, a thick bridge of around 200 million axons — the largest white matter structure in the brain.
Split-brain patients
In the 1940s and especially the 1960s, surgeons cut the corpus callosum in some patients with severe, uncontrollable epilepsy, to stop seizures spreading from one side to the other. Day to day, the patients seemed remarkably normal. But Roger Sperry and Michael Gazzaniga at Caltech designed clever tests that sent information to only one hemisphere — for instance by flashing a picture briefly to one side of the visual field.
When a picture went to the left hemisphere, patients could name it. When it went only to the right, they said they saw nothing — yet their left hand (controlled by the right hemisphere) could pick out the matching object. Each hemisphere had its own perceptions. In some experiments the left hemisphere confidently invented explanations for actions the right had performed — Gazzaniga called it the interpreter. Sperry received a share of the 1981 Nobel Prize.
What is lateralised
Language is strongly lateralised to the left hemisphere in about 95% of right-handers and roughly 70% of left-handers. The right hemisphere tends to dominate for aspects of spatial attention, face recognition and processing the emotional tone (prosody) of speech. Many functions involve both sides.
The myth of left- and right-brained people
From these findings grew a popular idea that people are "left-brained" (logical) or "right-brained" (creative). There is no good evidence for this. A 2013 University of Utah study analysing over 1,000 brain scans found that individuals don't show stronger overall networks on one side. Creativity and logic both draw on both hemispheres, working together through the corpus callosum.
Everyday examples & things to try
Picture it
Two pictures, two answers
In a classic split-brain test, a patient's left hemisphere sees a chicken claw and the right sees a snowy scene. Asked to choose related pictures, the right hand picks a chicken and the left hand a shovel. Asked why, the speaking left hemisphere — unaware of the snow — says: 'The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed.'
Key takeaways
- The corpus callosum links the hemispheres with about 200 million axons.
- Split-brain studies showed each hemisphere can perceive and act independently.
- Language is usually left-lateralised, but 'left/right-brained' personalities are a myth.
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