Behold the human brain, it's lumpy landscape visibly split into a left and right side. This structure has inspired one of the most pervasive ideas about the brain, that the left side controls logic and the right, creativity. And yet, this is a myth unsupported by scientific evidence. So how did this misleading idea come about, and what does it get wrong? It's true that the brain has a right and a left side. This is most apparent with the outer layer, or the cortex. Internal regions, like the striatum, hypothalamus, thalamus, and brain stem appear to be made from continuous tissue, but in fact, they're also organized with left and right sides. The left and the right sides of the brain do control different body functions, such as movement and sight. The brain's right side controls the motion of the left arm and leg and vice versa. The visual system is even more complex. Each eye has a left and right visual field. Both left visual fields are sent to the right side of the brain, and both right fields are sent to the left side. So the brain uses both sides to make a complete image of the world. Scientists don't know for sure why we have that crossing over. One theory is it began soon after animals developed more complex nervous systems because it gave the survival advantage of quicker reflexes. If an animal sees a predator coming from its left side, it's best off escaping to the right. So we can say that vision and movement control are two systems that rely on this left-right structure, but problems arise when we over-extend that idea to logic and creativity. This misconception began in the mid-1800s when two neurologists, Broca and Wernicke, examined patients who had problems communicating due to injuries. The researchers found damage to the patients' left temporal lobes, so they suggested that language is controlled by the left side of the brain. That captured the popular imagination. Author Robert Louis Stevenson then introduced the idea of a logical left hemisphere competing with an emotional right hemisphere represented by his characters Dr. Jekyll and Mr. Hyde. But this idea didn't hold up when doctors and scientists examined patients who were missing a hemisphere or had their two hemispheres separated. These patients showed a complete range of behaviors, both logical and creative. Later research showed that one side of the brain is more active than the other for some functions. Language is more localized to the left and attention to the right. So one side of the brain may do more work, but this varies by system rather than by person. There isn't any evidence to suggest that individuals have dominant sides of the brain, or to support the idea of a left-right split between logic and creativity. Some people may be particularly logical or creative, but that has nothing to do with the sides of their brains. And even the idea of logic and creativity being at odds with each other doesn't hold up well. Solving complex math problems requires inspired creativity and many vibrant works of art have intricate logical frameworks. Almost every feat of creativity and logic carries the mark of the whole brain functioning as one.
