Laterality is the tendency to favor one side of the body over the other. Most humans are right-side dominant, meaning that the left hemisphere of their brain, which controls the right side, is dominant over the right. The tendency to use one side over the other can be seen in a number of different body parts, including hands, feet, eyes and ears.
The side of the body that performs better at various tasks is called the dominant side. People who are right-handed, for example, draw and write faster and with more precision when using their right hand. People who are left-footed can kick a ball straighter and harder when using their left foot. Though most people show lateral dominance for one side or another, there are some people who are right-side dominant for some things and left-side dominant for others.
The most common sign of laterality in humans is right or left hand preference. Most children show a strong inclination to use one hand over the other at a very young age. There is even evidence that hand preference begins before birth, with the dominant hand being the one that is usually held close to the mouth. Approximately 88% of people are right-handed, while only 8%-15% are left-handed. There are a small percentage of people who are ambidextrous, meaning that both hands are dominant, and a small percentage who do not have a dominant hand.
Aside from hand-preference, foot and limb preference are also common signs of laterality. Foot dominance is especially important in sports such as surfing or snowboarding, where the dominant foot will lead on the board. Limb dominance is a common form of laterality that is observed in animals. Bone weight can be used to determine which limb is dominant in animals.
Laterality can also be seen in the preference for using one eye or ear over the other. Many people tilt their head towards the side of their dominant ear when listening intently. Eye dominance can be determined by holding one finger at arm’s length from the body and closing first one eye and then the other. If a person has one eye that is dominant, their finger will appear to jump to one side when they close their dominant eye.
There is a connection between mixed right and left dominance and many neurological disorders. These disorders can arise from mixed dominance because the brain is not cleanly organized between the hemispheres. People with mixed dominance can have problems such as distractibility, dyslexia, poor coordination or emotionality.