Your cerebral cortex has a big impact on how you think.

Image courtesy U.S. Department of Health and Human Services

Genius and the Brain

Your brain regulates your body's organ systems. When you move around, it sends impulses along your nerves and tells your muscles what to do. Your brain controls your senses of smell, taste, touch, sight and hearing, and you experience and process emotions using your brain. On top of all that, your brain allows you to think, analyze information and solve problems. But how does it make you smart?

Scientists haven't figured out exactly how all the gray matter in your brain works, but they do have an idea of which part lets you think. The cerebral cortex, which is the outermost part of your brain, is where thought and reasoning happen. These are your brain's higher functions -- the lower functions, which relate to basic survival, take place deeper in the brain.

Hover your mouse pointer over the labels to see where each lobe of the brain is located.

Your cerebral cortex is the largest part of your brain, and it's full of wrinkles and folds that allow it to fit in your skull. If you removed and stretched out an adult human's cerebral cortex, it would be about as large as a few pages of a newspaper. It's divided into several lobes, and different regions within these lobes handle specific tasks related to how you think. You can learn about them in more detail in How Your Brain Works, but here's a quick overview of what each lobe handles:

  • Frontal: speech, thought and memory
  • Parietal: sensory input from your body
  • Temporal: auditory information from your ears
  • Occipital: visual information from your eyes

It's obvious that your cerebral cortex has a big impact on how you think. But studying exactly how it makes you smart is a little tricky, because:

  • Your brain is hard to get to -- it's encased in your skull.
  • Tools for looking at the brain, such as magnetic resonance imaging (MRI) machines, can require a person to be partially or completely still. This can make it hard for doctors to observe people's brain activity during real-life activities.
  • Brains, like all organs, undergo changes after a person dies. These changes may make it difficult to tell how someone's brain compared to other brains while that person was alive. In addition, postmortem examinations cannot evaluate brain activity.

In spite of all those challenges, researchers have figured out a few things about how the brain affects intelligence. A 2004 study at the University of California, Irvine found that the volume of gray matter in parts of the cerebral cortex had a greater impact on intelligence than the brain's total volume. The findings suggest that the physical attributes of many parts of the brain -- rather than a centralized "intelligence center" -- determine how smart a person is.