The psychedelic experience research Houston and Masters conducted culminated in the 1966 publication of "The Varieties of Psychedelic Experience." The U.S. government banned psychedelic research that same year. This classic in psychedelic studies detailed the expanded cognition and creativity participants experienced under the influence of LSD. After the research ban, Houston and Masters shifted their focus to explore other ways of achieving altered states of consciousness without the use of drugs. Houston and Masters' 1972 book "Mind Games" detailed their findings that guided imagery and specific programs of bodily movement could reprogram the brain toward more integrated ways of experiencing the world. John Lennon called "Mind Games" "one of the two most important books of our time."