Hallucinogens are a large, diverse class of psychoactive drugs that can produce altered states of consciousness characterized by major alterations in thought, mood, and perception as well as other changes. Most hallucinogens can be categorized as either being psychedelics, dissociatives, or deliriants. However, certain hallucinogens such as Fly agaric as well as other gabaergic hallucinogenics are more often considered to technically be hypnotics, therefore indicating another separate subcategory of drugs which can substantially alter visual perception.