Kim Peek was born with macrocephaly, damage to the cerebellum, and, perhaps most important, agenesis of the corpus callosum, a condition in which the bundle of nerves that connects the two hemispheres of the brain is missing; in Peek’s case, secondary connectors such as the anterior commissure are also missing. There is speculation that his neurons make other connections in the absence of a corpus callosum, which results in an increased memory capacity. According to Peek’s father, Fran, Peek was able to memorize things from the age of 16-20 months. He read books, memorized them, and then placed them upside down on the shelf to show that he had finished reading them, a practice he still maintains. He reads a book in about an hour, and remembers almost everything he has read, memorizing vast amounts of information in subjects ranging from history and literature, geography, and numbers to sports, music, and dates. His reading technique consists of reading the left page with his left eye and the right page with his right eye and in this way can read two pages at time with a rate of about 8-10 seconds per page. He can recall the content of some 12,000 books from memory.

Peek resides in Salt Lake City, Utah. He is a member of The Church of Jesus Christ of Latter-day Saints.