What is the relationship of savant syndrome to IQ?
When Dr. Down originally named the condition idiot savant, he linked its name with a classification of IQ of less than 25, but almost all reported cases have occurred in persons with an IQ above 40. However a low measured IQ score, or “mental retardation” either as a symptom or separate disorder, is not what determines whether a person is or is not a savant. Instead the term savant syndrome encompasses a number of different mental disabilities including, but not limited to, the separate disorder of mental retardation itself. When applied to savant syndrome, the term “mental disability” can include disorders as Autism, Asperger’s, Hyperlexia or Williams Syndrome, for example. In some of these individuals measured IQ can be normal or even superior, although when that is the case, usually the IQ sub-scores show a wide scatter among the various sub-tests that make up the overall IQ test battery with some sub-tests showing severe limitations and other showing extremely high scores. Thus a low IQ score, while often present in savant syndrome, is not necessarily the case in all instances, and it is not a finding essential or requisite to savant syndrome. Some savants do score in the normal or superior range on commonly used IQ tests, or at least on some of the sub-tests that make up the overall IQ test battery.
IQ is a measure of so-called “general intelligence.” While some scatter is common in most individuals on the sub-tests of the IQ test battery, sub-test scores do tend to cluster in certain ranges for a given individual producing, when averaged, an overall ‘general’ intelligence score, or IQ. That IQ score does tend to be correlated with a general level of overall intellectual functioning. But the very wide scatter of abilities seen in some savants on the IQ sub-scores, which is much more pronounced than in most persons, has raised the question of whether it would be more accurate to view all persons as a series of multiple intelligences, rather than having what has been designated general intelligence, or IQ. Indeed some investigators view savants as refuting the notion of “general intelligence” and argue, instead, that each of us have multiple intelligences and testing and measurement of “IQ” in all people should be revised to reflect that reality.
Further, in viewing “mental retardation” one needs to differentiate between “actual” retardation (measured IQ below 70) and “functional” retardation. The latter can occur in someone with seemingly normal or even superior intellectual capacity whose mental disability, from whatever etiology, causes them to function at a much lower level overall than one might expect from estimated or even measured IQ. It is not uncommon to see some autistic individuals, for example, function at a superior level in some areas such as mathematics, verbal skills or memory, but be so severely disabled in other areas so as to “function” at much lower level overall. The present IQ sub-tests, such as digit span, for example, are not sufficiently tailored to realistically assess certain areas of superior function in savants, and do need to be revised and tailored accordingly to be able to get a true measure of savant capabilities for comparative studies in the area of “0intelligence.”
In summary, measured IQ levels in savant syndrome most often are below 70. However while savant syndrome can occur in persons where mental retardation is the basic CNS disorder, savant syndrome can also be seen in individuals with IO’s below 70 as a finding or symptom where the basic developmental disorder is instead Autism, Asperger’s, Hyperlexia, PDD or Williams Syndrome, for example, or a number of other conditions following CNS injury or disease. While it is true that in most persons with savant syndrome measured IQ is below 70, savant syndrome includes a number of mental disorders in which IQ function, in scattered areas of functioning at least, can be normal or even superior. In short, savant syndrome is not synonymous with, nor limited to mental retardation, and in some persons with savant syndrome IQ can be in the normal, or even superior range.