An autistic savant (historically described as idiot savant) is a person with both autism and savant syndrome. Savant syndrome describes a person having a severe developmental or mental handicap with extraordinary mental abilities not found in most people. This means a lower than average general intelligence (IQ) but very high narrow intelligence in one or more fields. Savant syndrome skills involve striking feats of memory and arithmetic calculation and sometimes include unusual abilities in art or music. Savant syndrome is sometimes abbreviated as "savantism", and individuals with the syndrome are often nicknamed savants. This can be a source of confusion since a savanter is a person of learning, especially one of great knowledge in a particular subject.
Savant syndrome is usually recognized during early childhood as coincident with other developmental abnormalities; the plurality of cases occur in children with autism. Males with savant syndrome outnumber females by roughly 6:1—slightly higher than the disparity for autism spectrum disorders.
Most autistic savants have extensive mental abilities called splinter skills. However, it is important to notice that people with a high general intelligence can demonstrate the same skills; savant disabilities are not necessary for these skills. They can recall facts, numbers, license plates, maps, and extensive lists of sports and weather statistics after only being exposed to them once. Some savants can mentally note and then recall perfectly a very long sequence of music, numbers, or speech. Some, dubbed mental calculators, can do exceptionally fast arithmetic, including prime factorization. Other skills include precisely estimating distances and angles by sight, calculating the day of the week for any given date over the span of tens of thousands of years, and being able to accurately gauge the passing of time without a clock. Most autistic savants have a single special skill while others have multiple skills. Usually these abilities are concrete, non-symbolic, right hemisphere skills as opposed to left hemisphere skills that tend to be more sequential, logical, and symbolic.
Why autistic savants are capable of these astonishing feats is not quite clear. Some savants have obvious neurological abnormalities (such as the lack of corpus callosum in Kim Peek's non-autistic brain). Many savants are known to have abnormalities in the left hemisphere of the brain. 
There are only about 50–100 recognized prodigious savants in the world.
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