Scientists have been aware for at least 100 years that each side of the brain controls actions on the opposite side of the body. However, it was not until the 1950s that Roger Sperry (1913–1994) conducted the pioneering research to determine the different functions of the left side and right side of the brain. His experiments contributed to the “split-brain” theory. Sperry received the Nobel Prize in Physiology or Medicine in 1981 for his work.