Scientists in Australia say they've identified the gene that causes the behaviour exhibited by Dustin Hoffman's character in Rain Man.
Contrary to popular belief, the real-life inspiration for Raymond Babbitt wasn't autistic. Kim Peek instead suffered from FG syndrome, a genetic abnormality that left him without a corpus callosum - a fibre bridge between the two hemispheres of the brain.
Despite his intellectual disabilities, Mr Peek had an incredible memory and could read a book two pages at a time - one with the left eye, the other with the right.
Around one-in-4000 babies has the mutation, which can also result in 'mirror movements' - moving one hand results in the other doing the exact same thing, only mirrored.
Associate Professors Paul Lockhart and Rick Leventer at the Murdoch Childrens Research Institute in Melbourne say abnormalities in the gene they've found causes the loss of the corpus callosum, even if nothing else is wrong.
It's believed the brain's attempt to make up for the loss of the corpus callosum, by making new connections where there wouldn't normally be any, results in the kind of savant abilities shown by Mr Peek.
"Our research provides important new information about how nerves connect to the appropriate part of the brain during development of the embryo," said Assoc Prof Lockhart.
"This has potential implications for our understanding of a broad range of neurodevelopmental conditions such as autism spectrum disorder."
"The outcomes are very variable, from patients with normal intellect to patients with severe disabilities and the entire spectrum in between," said Assoc Prof Leventer.
"One of the tangible benefits of our discovery is that we might be able to reassure parents whose child has [no corpus callosum] due to a mutation in the gene, that these children are usually unaffected or only mildly affected, as our study shows."
The condition has been linked to autism, with scans of people on the autism spectrum showing unusual - or absent - links between different parts of the brain.
The research is published Tuesday in journal Nature Genetics.