The problem
After a suggestion of arm rigidity, someone may try to bend an arm yet feel it resist. The unresolved question is which processes produce that change in action and in the sense of agency, the feeling of initiating or controlling an action. Preparation for hypnosis and the particular instruction need separate explanations.
A 2026 study compared rest, hypnotic induction and suggested arm rigidity with awake voluntary simulation. It combined electrical brain recordings, or EEG, with physiological measures and reports of experience. Differences among phases and responses constrain explanations; they do not identify a causal circuit or one mechanism for every kind of suggestion.[1] [2]
Scope
Mechanisms of human responses to hypnotic suggestions affecting perception, action or agency, separating induction effects, suggestion type and individual responsiveness.
What remains open
In an arm-rigidity study, people reported stiffness while their movements and brain recordings varied. Such measurements show differences between responses, but do not establish what produces the feeling or why people respond differently. A proposed explanation must account for both the experience and the action.[1] [2]
Brain recordings can vary with an induced experience without showing which change causes it. The arm-rigidity results also leave open how similar experiences accompany different movements. A later scoping review proposes a framework based on predictions and sensory information, but organizing observations into that account does not establish its causal explanation. Tests must distinguish competing processes across people and suggestion types.[1] [2] [3]
Why it matters
An arm held straight deliberately and an arm experienced as rigid after a suggestion can look similar while feeling different. Explaining that contrast would connect a person’s experience of authorship to the processes controlling action. It gives a concrete way to study how language and expectation affect conscious control, while checking whether the account explains perception and other suggestions as well.[1] [2]
Definitions
Sources
- How hypnotic suggestions work – A systematic review of prominent theories of hypnosis
Notes on How hypnotic suggestions work – A systematic review of prominent theories of hypnosis
A systematic comparison credits established suggestion effects while identifying strengths and limitations of competing mechanistic theories.
- Decoding hypnotic consciousness: neural and experiential insights into induced and ideomotor suggestions
Notes on Decoding hypnotic consciousness: neural and experiential insights into induced and ideomotor suggestions
EEG, physiological measures and first-person reports compare induction, arm rigidity and awake voluntary control; associations and interpretations leave causal mechanisms open.
- Shared neural mechanisms of trait mindfulness and hypnotic susceptibility: A scoping review toward a unifying predictive coding framework
Notes on Shared neural mechanisms of trait mindfulness and hypnotic susceptibility: A scoping review toward a unifying predictive coding framework
First online June 27, September 2026 issue. The proposed predictive-coding framework organizes existing evidence and remains a hypothesis requiring tests.