A preference for using one hand rather than the other to perform most manual tasks and activities. Most people are right-handed. Historically, it has been theorized that handedness is associated with a dominance of the opposite cerebral hemisphere of the brain, but this has not been conclusively proven. Although the scientific basis for handedness is unknown, the fact that left-handed parents more frequently have left-handed offspring suggests at least a partial genetic component. Some experts believe that children are trained to favor one hand over the other (usually the right hand.). Handedness is usually established in the first few years of life.