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Stanislav Grof is a psychiatrist who has primarily researched non-ordinary states of consciousness. He has developed a model of consciousness that includes four basic states: waking, dreaming, deep sleep, and what he calls "transpersonal" states. These transpersonal states are characterized by experiences such as out-of-body experiences, near-death experiences, and mystical experiences. Grof believes that these states are important for personal growth and healing.