Entheogens are psychoactive substances that induce alterations in perception, mood, consciousness, cognition, or behavior for the purposes of engendering spiritual development or otherwise in sacred contexts. Anthropological study has established that entheogens are used for religious, magical, shamanic, or spiritual purposes in many parts of the world. Entheogens have traditionally been used to supplement many diverse practices geared towards achieving transcendence, including divination, meditation, yoga, sensory deprivation, healings, asceticism, prayer, trance, rituals, chanting, imitation of sounds, hymns like peyote songs, drumming, and ecstatic dance. The psychedelic experience is often compared to non-ordinary forms of consciousness such as those experienced in meditation, near-death experiences, and mystical experiences. Ego dissolution is often described as a key feature of the psychedelic experience.