Neither exactly. Hypnosis is a state (or set of processes) that can produce experiences similar to hallucinations or illusions, but it is best described as a change in attention, suggestibility, and expectation that alters perception, memory, thought, and behavior.
Explanation, organized:
Definitions
Illusion: a misperception of a real external stimulus (e.g., seeing a rope as a snake). The stimulus exists but is perceived incorrectly.
Hallucination: a perceptual experience in the absence of an external stimulus (e.g., hearing voices when no one is speaking).
Hypnosis: not a single phenomenon but a collection of processes produced by suggestion, social interaction, and cognitive changes. Common features include focused attention, reduced peripheral awareness, increased responsiveness to suggestions, and altered control over thoughts, sensations, and actions.
How hypnosis relates to illusions and hallucinations
Hypnotically induced perceptions can resemble hallucinations: under suggestion, people can report seeing, hearing, smelling, or feeling things that have no external source. Example: a hypnotized person is told “you see a pink elephant,” and they report a vivid image or even behavior consistent with seeing one. That is phenomenologically like a hallucination because there is a perception without the corresponding external stimulus.
Hypnosis can also create illusion-like distortions: for instance, suggestions that a hand feels heavier or colder alter perception of an actual sensory input rather than creating a wholly new object; that resembles an illusion (misperception of a present stimulus).
Crucially, hypnotic experiences are often suggestion-driven and are frequently voluntary or contextually bound: the person usually accepts or expects the suggested experience, and it often reverses when suggestion stops. That distinguishes many hypnotic experiences from spontaneous clinical hallucinations (e.g., in psychosis), which are not typically suggestion-dependent or under voluntary control.
Mechanisms
Attention and expectation: focused attention and expectation amplify certain internal representations and suppress others, changing what reaches conscious awareness.
Top-down processes: suggestion acts as a top-down influence that biases perceptual systems to produce particular experiences or to reinterpret incoming signals.
Dissociation and altered agency: hypnotic suggestions can reduce voluntary control or sense of authorship, making experiences feel automatic or “real” to the subject.
Clinical and experimental evidence
Neuroimaging shows that hypnotic suggestions can modulate activity in sensory cortices and in networks related to attention and executive control. For example, suggested deafness reduces auditory cortex responses; suggested paralysis alters motor-related activity. These findings support the idea that hypnosis changes both perception and its neural correlates.
In lab studies, hypnotically induced “hallucinations” can be phenomenally vivid and behave like genuine perceptions in many tests (e.g., affecting behavior, memory, or reaction times), yet they are often more pliable and suggestion-sensitive than pathological hallucinations.
Practical implication
For understanding or treating symptoms, it’s useful to distinguish: hypnotic phenomena are typically situational, suggestion-dependent, and reversible. Pathological hallucinations (e.g., in schizophrenia) usually have different causes, less voluntary control, and different clinical management.
Bottom line
Hypnosis can produce experiences that are like hallucinations (perceptions without external stimuli) or like illusions (distortions of real stimuli), but hypnotic phenomena are better characterized as suggestion-driven alterations of attention, expectation, and cognitive control rather than being purely hallucination or illusion.