When Kim Peek was 9 months old, doctors pronounced him so mentally retarded that he would never walk or talk. One physician suggested he be institutionalized; another later recommended a lobotomy. Peek, who died of a heart attack Dec. 19 at 58, was indeed riven by disabilities throughout his life. Born without a corpus callosum--the nerve tissue that connects the brain's hemispheres--he never learned to brush his hair or button his shirt without help.
But buried beneath these afflictions was a mighty intellect unique in the world. Peek was a so-called megasavant, a man with such dazzling recall that he seemed...