When Kim Peek was a baby, doctors told his parents that he was severely mentally retarded, and may never be able to learn anything. Despite that diagnosis, Peek was reading entire encyclopedias by the age of four. Peek was known as a "megasavant," which meant he had an amazing memory and ability to learn. By age 10, he could read both pages of an open book at once, with one eye reading one page and the other eye reading the opposite page. He retained about 98% of everything he ever learned. By the time of his death in 2009 at age 58, Peek —who was nicknamed "The Kim-puter"— had read 12,000 books, according to his obituary in the New York Times. His abilities may have been due to a lack of connection between his brain's two hemispheres. "He was missing the corpus callosum, the sheaf of nerve tissue that connects the brain's hemispheres. It has been theorized that this disruption of normal communication between the brain's left and right halves resulted in a kind of jury-rigged rewiring," the Times reported.
In Scientific American, two experts on savants explained the potential cause of Kim's abilities like this: ""Perhaps the resulting structures allow the two hemispheres to function, in certain respects, as one giant hemisphere, putting normally separate functions under the same roof, as it were. If so, then Peek may owe some of his talents to this particular abnormality."