For Patients/Families

Handedness
The tendency to use one hand more than another. Most babies start out using both hands equally, but will have developed a preference by 1 year of age. Although it is not known exactly what causes us to prefer one hand over another, it is thought to be genetic and is associated with development of the right and left hemispheres of the brain. About 70% of people are right handed, 10% left handed, and 20% are ambidextrous (use each hand equally).