ELI5: Explain Like I'm 5

neuroanatomy of handedness

Okay kiddo, let's start with the basics. Our brain controls everything we do, including how we use our hands. Handedness simply means whether we prefer to use our left or right hand more for tasks like writing, throwing, or drawing.

Now, the part of the brain that controls our motor functions (or movement) is called the motor cortex. This area is in the outer layer of our brain, called the cerebral cortex. The motor cortex is divided into two main parts - the left motor cortex and the right motor cortex.

Here's where it gets interesting - the left motor cortex controls the right side of our body, and the right motor cortex controls the left side of our body! So if you want to raise your left hand, your brain sends a signal from the right motor cortex to the muscles in your left arm.

Scientists have found that most people have a dominant hand - that means they prefer to use one hand over the other for most tasks. About 90% of people are right-handed, and 10% are left-handed.

So, what makes us left or right-handed? Well, researchers believe that it has to do with how our brain is structured. They've found that certain areas of the brain associated with language and spatial skills are larger in the left hemisphere of the brain for most people, while areas associated with visual and emotional processing are larger in the right hemisphere.

This may explain why most people are right-handed - the left hemisphere of the brain is better at controlling fine motor skills like writing and drawing, which are often associated with language.

However, some left-handed people have a larger left hemisphere, which may explain why they prefer to use their left hand. And some people are ambidextrous, meaning they can use both hands equally well - scientists think this may be because their brain is more evenly balanced between the two hemispheres.

So there you have it - handedness is controlled by different areas of the brain, and most people are right-handed because of the way their brain is structured. But some people are left-handed, and others can use both hands equally well!