Savant syndrome (formerly called idiot savant syndrome) refers to an exceedingly rare but remarkable condition in which persons with severe mental handicaps have some isolated but spectacular islands of genius or brilliance that stand in stark, incongruous contrast with the serious limitations of the overall handicaps. The mental handicap can be either autism or mental retardation. The skills, remarkable as they are, exist within a very narrow range of human abilities. They include music (usually piano); art (drawing or sculpting); calendar calculating (the ability to give the day of the week for any past or future date); lightning calculating (the ability to add, multiply, subtract, or divide complex numbers with lightning rapidity); and mechanical or spatial skills including map memorizing, visual measurement, unusual sensory discrimination such as enchanced sense of touch and smell, or perfect appreciation of time without knowledge of a clock. These skills, within these very narrow bands, are always linked to a spectacular memory.
In some persons (talented savants) the skills are remarkable simply in contrast with the handicap; in others (prodigious savants) the abilities are spectacular in contrast with the handicap and would be spectacular even if they occurred in normal persons. Savant syndrome can be hereditary or it can be acquired following central nervous system injury before, during, or after birth. It occurs in males approximately six times more frequently than in females. The skills can appear suddenly, without explanation, and can disappear just as suddenly.
The condition was first described in 1887 by J. Langdon Down (better known for having described Down syndrome). He was struck by the paradox of deficiency and superiority in a number of cases he saw as superintendent of a hospital in England. At that time in Britain the word idiot was an accepted legal classification for a severe degree of mental retardation and did not have the pejorative, comical connotation the term now has. Down combined that word with the term savant—knowledgeable person—derived from the French word savoir (to know), to denote these fascinating persons. The term is a misnomer in that almost all cases have an IQ of 40 or above, and thus have moderate rather than the severe mental retardation that now-archaic legal term idiot once defined.
Superior memory is a trait all savants share. It is a particular type of memory, however: very deep but within a very narrow area; concrete and not richly associative; direct and nonsymbolic; nonemotional and seemingly automatic or unconscious. This "memory without reckoning" may be akin to what Mishkin, Malamut, and Bachevalier (1984) refer to as "habit" memory, as opposed to "cognitive" memory; it relies on a brain circuitry that is more primitive and lower than the later-developed, higher brain circuitry of cognitive or associative memory. In the savant this unconscious memory presumably is relied upon as an alternative pathway to damaged higher-level cognitive memory circuitry.
There has been no well-designed study of the prevalence of savant syndrome, but it has been reported to occur in 1 out of 2,000 in an institutionalized mentally retarded population and in as many as 1 out of 10 autistic persons. Mental retardation and autism are both developmental disabilities, but since autism is so much less common than mental retardation, the number of savants is generally evenly divided between those with autism and those with mental retardation. In the movie Rain Man, the character Raymond Babbit (played by Dustin Hoffman) is the best-known portrayal of a savant, in that instance an autistic savant. It is important to remember, however, that not all autistic persons are savants and not all savants are autistic. The number of prodigious savants worldwide is estimated to be less than fifty as of 1991. Talented savants are, of course, more common; but the savant syndrome overall is still a rare condition.
Mishkin, M., Malamut, B., and Bachevalier, J. (1984). Memories and habits: Two neural systems. In G. K. Lynch, J. L. McGaugh, and N. M. Weinberger, eds., Neurobiology of learning and memory. New York: Guilford Press.
Treffert, D. A. (1988). The idiot savant: A review of the syndrome. American Journal of Psychiatry 145 (5), 563-572.
—— (1989). Extraordinary people: Redefining the "idiot savant." New York: Harper & Row.
—— (1990). Extraordinary people: Understanding savant syndrome. New York: Ballantine Books.