A<unk>  is a perception in the absence of an external stimulus that has the qualities of a real perception.<unk> s are vivid, substantial, and are perceived to be located in external objective space. They are distinguishable from several related phenomena, such as dreaming, which does not involve wakefulness; pseudohallucination, which does not mimic real perception, and is accurately perceived as unreal; illusion, which involves distorted or misinterpreted real perception; and imagery (imagination), which does not mimic real perception, and is under voluntary control.<unk> s also differ from "delusional perceptions", in which a correctly sensed and interpreted stimulus (i.e., a real perception) is given some additional significance. Many<unk> s happen also during sleep paralyses.<unk> s can occur in any sensory modality—visual, auditory, olfactory, gustatory, tactile, proprioceptive, equilibrioceptive, nociceptive, thermoceptive and chronoceptive. A mild form of<unk>  is known as a disturbance, and can occur in most of the senses above. These may be things like seeing movement in peripheral vision, or hearing faint noises or voices. Auditory<unk> s are very common in schizophrenia. They may be benevolent (telling the subject good things about themselves) or malicious, cursing the subject. 55% of auditory<unk> s are malicious in content, for example, people talking about the subject, not speaking to them directly. Like auditory<unk> s, the source of the visual counterpart can also be behind the subject. This can produce a feeling of being looked or stared at, usually with malicious intent. Frequently, auditory<unk> s and their visual counterpart are experienced by the subject together. Hypnagogic<unk> s and hypnopompic<unk> s are considered normal phenomena. Hypnagogic<unk> s can occur as one is falling asleep and hypnopompic<unk> s occur when one is waking up.<unk> s can be associated with drug use (particularly deliriants), sleep deprivation, psychosis, neurological disorders, and delirium tremens. The word<unk> " itself was introduced into the English language by the 17th-century physician Sir Thomas Browne in 1646 from the derivation of the Latin word alucinari meaning to wander in the mind. For Browne,<unk>  means a sort of vision that is "depraved and receives its objects erroneously".
Hallucination
Mindfulness
Automatism 
Perseveration
Bullying
Emotional detachment
Musical hallucinations
Intrusive thought