Savant syndrome (formerly, idiot savant) is used to describe persons who have musical, artistic or mathematical talent despite other obvious cognitive impairments, such as mental retardation, autism, or severe brain damage. For example, the patient in Half Wit was able to play the piano perfectly, remember a composition after hearing it played once, had absolute pitch, and was able to complete musical compositions started by someone else. However, he also was unable to button his own shirt, carry on a conversation, and had difficulty focusing on tasks.
There is no explanation for why some persons can exhibit talents and mental abilities well beyond persons with even superior intelligence, yet still be mentally impaired. However, such persons are studied closely by doctors in order to attempt to gain insight into the workings of the human brain.