Delayed Development of Hemispheric Dominance

In recent years much has been written about the relation between speech function and hemisphere dominance, in connection with aphasia. There has, however, been little clarification of the neurological substrate of delayed acquisition of hemisphere dominance. In this report, it is proposed to demonstrate a common relationship between cerebral disease and the delayed development of hemisphere dominance as judged by delay in the development of speech and handedness. The concept of a leading or dominant hemisphere has attracted the attention of neurologists for over a century. The concept of the right hand as the master hand goes back into antiquity and references to this are found in Semitic religious writings. About 90% to 95% of the population is right-handed.1,2There would appear to be two principal mechanisms for the development of lefthandedness. The first is heredity1and the second is damage to the left cerebral hemisphere, during