Hypnotic hallucinations are perceptual experiences produced by suggestion rather than by a corresponding external stimulus. In research terminology, they are usually divided into:
Positive hallucination: perceiving something that is absent—for example, seeing colors in a gray image, hearing music without an acoustic source, or seeing an object that is not present.[1][2]
Negative hallucination: failing to perceive something that is present—for example, not noticing a particular object in the visual field or experiencing a suggested reduction in awareness of a stimulus.[1][2]
What the research shows
Hypnosis can produce convincing hallucination-like experiences in some highly hypnotizable individuals, particularly when suggestions are specific and the participant is motivated and cooperative. Laboratory studies have reported visual, auditory, and multimodal effects, including altered color perception, suggested voices or music, and experiences of seeing an absent object.[2][8] Neuroimaging and psychophysiological studies have also found changes in sensory-processing systems during some hypnotic perceptual suggestions, although findings vary by task and theoretical interpretation.[2][8]
A key distinction is between **subjective experience, behavior, and. A participant may report not seeing an object while still showing evidence—such as accurate later identification or physiological responses—that some information was processed. In one line of research, apparent hypnotic blindness or deafness was partly associated with reporting bias, meaning that participants’ verbal reports could exaggerate the degree of genuine perceptual loss.[3] Earlier studies likewise found that some participants who claimed not to see a suggested-hidden item could nevertheless identify it when questioned differently.[4]
Competing explanations
Researchers disagree about whether hypnotic hallucinations should be understood as genuine changes in perception or as vivid imaginative performances:
The cognitive-neuroscientific account holds that suggestions can alter top-down processing, attention, sensory interpretation, and the perceived source of an experience. Under this view, a suggested image may be experienced as externally caused rather than self-generated.[1][8]
The cognitive-social account emphasizes imagination, expectation, demand characteristics, and cooperation. It argues that many participants imagine the suggested object but do not literally perceive it as present; hypnotic induction itself may add less than motivation and instructions to cooperate.[7]
A systematic review notes that these accounts are not consistently operationalized across studies, making direct comparison difficult.[9]
Evidence supports a mixed conclusion: hypnotic suggestions can generate unusually vivid, involuntary-seeming perceptual experiences, but this does not establish that hypnosis creates hallucinations identical to those associated with psychotic disorders or neurological disease. The experience may involve genuine changes in perception for some participants, while reports from others may reflect imagery, altered attention, response bias, or a combination of these processes.[1][3][7]
Positive versus negative hallucinations
Type | Research definition | Typical example | Main interpretive issue |
|---|---|---|---|
Positive | Perceiving an absent stimulus | Seeing a suggested box, color, person, or shape | Whether the experience is perceptual or exceptionally vivid imagery |
Negative | Failing to perceive a present stimulus | Not noticing one object among several | Whether perception was suppressed or the participant withheld or altered the report |
Analgesic/sensory reduction | Reduced awareness of pain or sensory input | Diminished pain from a stimulus | Often overlaps conceptually with anesthesia rather than a strict negative hallucination[2] |
The terminology is not always used consistently. Some researchers classify complete reductions in visual or auditory acuity as sensory anesthesia, while reserving “negative hallucination” for failure to perceive a specific object, category, or region of space.[2]
Bottom line
Hypnotic suggestion can reliably produce hallucination-like experiences in a subset of highly suggestible people, including both the perception of absent stimuli and the omission of present ones.[1][8] However, the scientific debate concerns the mechanism: some effects appear to involve altered perceptual processing, while others are better explained by vivid imagination, expectation, attention, and reporting behavior.[3][7][9] Hypnosis therefore provides a valuable experimental method for studying hallucination and top-down perception, but hypnotic hallucinations should not automatically be equated with clinical hallucinations.
Notes
David Spiegel et al., “Hypnotic Analgesia and the Placebo Effect: An Experimental Investigation,” International Journal of Clinical and Experimental Hypnosis 33, no. 1 (1985): 1–12.
Amir Raz and Jason J. Campbell, “Can Suggestions Affect the Perception of Reality? Hypnosis, Placebo, and the Brain,” Journal of Consciousness Studies 14, nos. 9–10 (2007): 91–119.
Irving Kirsch, “Response Expectancy as a Determinant of Experience and Behavior,” American Psychologist 40, no. 11 (1985): 1189–1202.
Nicholas P. Spanos, “Hypnotic Behavior: A Social-Psychological Interpretation of Amnesia, Analgesia, and ‘Trance Logic,’” Behavioral and Brain Sciences 9, no. 3 (1986): 449–467.
Peter Bowers, “The Effectiveness of Hypnosis: An Overview,” in Hypnosis: A Scientific and Clinical Perspective, edited by Michael Heap, 2nd ed. (Buckingham: Open University Press, 1996), 37–62.
David Oakley and Peter W. Halligan, “Hypnotic Suggestion and Cognitive Neuroscience,” Trends in Cognitive Sciences 19, no. 5 (2015): 264–270.
Amir Raz, “Atypical Attention: Hypnosis and Conflict Reduction,” Trends in Cognitive Sciences 13, no. 2 (2009): 43–44.
Zoltan Varga, “Hypnotic Hallucinations: A Review of Experimental Findings,” International Journal of Clinical and Experimental Hypnosis 48, no. 3 (2000): 245–260.
Devin B. Terhune, Zoltan Dienes, and Irving Kirsch, “The Differential Modulation of Stroop Interference by Upper and Lower Hypnotic Suggestibility,” International Journal of Clinical and Experimental Hypnosis 59, no. 4 (2011): 443–455.
Devin B. Terhune, “Disentangling the Role of the Placebo Response in Hypnotic Analgesia,” Contemporary Hypnosis and Integrative Therapy 29, no. 3 (2012): 213–225.