According to Hypnosis and Suggestion, hypnosis is a process through which subjects become susceptible to suggestion. The two main theories that explain the hypnotic trance are referred to as state and non-state theories. They respectively argue that hypnosis is either a dissociative state or a relaxed state that accepts suggestion.
Two major 20th-century psychologists, Earnest Hilgard and Theodore Sarbin, are often linked to or credited with the state and non-state theories regarding hypnosis. As Hypnosis and Suggestion relates, Hilgard was a proponent of State theories alone, while Sarbin wrote about non-state theories that several theorists have continued to build on their ideas. Both psychologists held that hypnosis could be effective.
In the mid 20th-century, Sarbin published research papers stating that the hypnotic state was not so much an altered consciousness, but a role played by the person hypnotized. This did not mean that the trance was fake, only that the subject of hypnosis sheds inhibitions and willingly accepts suggestions while normal brain function is occurring.
Hilgard later proposed that the hypnotic state actually changes the cognitive processing of the subject. Psychologist Kendra Cherry summarizes Hilgard's Neodissociation Theory as stating that the mental functions of hypnotized persons are split in two: one consciousness acts on suggestions made by the hypnotist, while the second is free to process and interpret insights that would normally be outside of the subject's consciousness.