It is perhaps most well-known in connection with the film Rain Man in which Dustin Hoffman played an autistic savant. There are only a small number of autistic savants in the world and they are said to have a remarkable spatial and numeric abilities. Some 40 million people in the world are autistic and, although it is thought to have been around for centuries, the numbers are said to be rising. This may, however, be because of better diagnosis. Males are up to four times more likely to suffer from the condition than females.
Possible causes are genetic, viral or metabolic, with triggers including German measles.
It is also linked to epilepsy and there may be an association between difficult labour and autism. Controversially, a UK study has suggested a link between the mumps, measles and German measles vaccine and autism, but health experts say this has not been proven. Imagination Autism is a lifelong learning disability associated with an inability to understand others' feelings and difficulty in the development of play and the imagination and communication problems. For this reason, the NAS says the internet has been a particular boon. They also have difficulty understanding speech which might be less logical and less linear than written language.