A hallucinogen is a psychoactive agent which can cause hallucinations, perception anomalies, and other substantial subjective changes in thoughts, emotion, and consciousness.The common types of hallucinogens are psychedelics, dissociatives, or deliriants. By contrast, Stimulants, Opioids, and other psychoactive drugs are not explicitly hallucinogens because a 'hallucination' is visual terminology. The psychoactivity of opioids is devoid of visual anomalies, though the 'numbing' can be considered dissociation from pain. Hallucinations are not an uncommon symptom of amphetamine psychosis, but as they are not a primary effect of the drugs themselves, amphetamines are not considered hallucinogens. While stimulants do not induce hallucinations without abuse, the nature of stimulant psychosis is not unlike delirium.