Before you can understand why many of us favor one side of our body, it helps to understand the complexity of the brain's structure and how it functions. The brain comprises two identical hemispheres. Certain parts of each hemisphere operate the same functions, such as sensory and visual perception, as well as motor control for the opposite side of the body. However, each hemisphere has unique functions that are not necessarily represented in the other hemisphere. For example, the ability to understand and process language is located in an individual's dominant hemisphere.
Healthy individuals use both hemispheres but favor one, especially during times of stress.
Experts disagree, however, over whether we are born with this preference or develop it at a very early age. These neurons join the left and right hemispheres and act like a bridge, transporting information from one hemisphere to the other. In addition, we also favor one eye, ear, hand, and foot over the other. Therefore, everyone has a highly individualized set of preferences for learning, processing information, and moving. And we can make no generalization relating brain-side preference to turn preference.