Glossary

This glossary is intended to be as comprehensive as possible. If there are any terms you would like to see added then please get in touch.

Dissociation

A term commonly used in the context of hypnosis by Pierre Janet. Dissociation refers to the separation of thoughts, emotions, memories or sensations from normal consciousness.
Dissociative tendency, the propensity to experience dissociative phenomena as part of everyday life, is measured using the Dissociative Experiences Scale (DES). You can obtain a copy of the DES here.
Recently there has been more consideration of dissociation, with a proposal by one team to separate it into 'detachment' and 'compartmentalisation' (Holmes et al, 2005).

functional Magnetic Resonance Imaging (fMRI)

A method for noninvasively measuring blood flow within the brain - a proxy for measuring brain activity directly. The machine takes advantage of the fact that oxygenated blood has slightly different magnetic properties from blood depleted in oxygen, and measures the relative effect by assessing distortions in an extremely sensitive magnetic field. fMRI has a much higher temporal resolution than PET, meaning that it can measure activity in the brain on a much shorter time scale (typically 1-4s, compared to 60-90s for PET).

Hypnosis

The term 'hypnosis' denotes an interaction between one person, the 'hypnotist', and another person or people, the 'subject' or 'subjects'. In this interaction the hypnotist attempts to influence the subjects' perceptions, feelings, thinking and behaviour by asking them to concentrate on ideas and images that may evoke the intended affects. The verbal communications that the hypnotist uses to achieve these effects are termed 'suggestions'. Suggestions differ from everyday kinds of instructions in that they imply that a 'successful' response is experienced by the subject as having a quality of involuntariness or effortlessness. Subjects may learn to go through the hypnotic procedures on their own and this is termed 'self-hypnosis' (British Psychological Society, 2001).

Induction

A hypnotic induction consists of instructions and suggestions given by a hypnotist which enable a participant or patient to become hypnotised

Meta-analysis

Literally 'studies of studies'. A meta analysis combines the results of a number of individual studies, and takes advantage of the reliability conferred by by a larger sample size.

Positron Emission Tomography (PET)

One method for measuring blood flow within the brain - a proxy for measuring brain activity directly. With PET a radioactive tracer (usually saline) is injected just before a scan, and flows into the brain. Emitted radiation is measured and its source reconstructed in three dimensions, producing a 'map' of brain activity during the period of measurement.

Post-hypnotic suggestion

A suggestion which is set to be activated upon a certain cue after the termination of hypnosis. Examples are included in many major hypnotic susceptibility scales, including the Stanford and Harvard Scales of Hypnotic Susceptibility.

Read an interview with Dr Amanda Barnier about some of her work researching post-hypnotic suggestions.

Randomized Controlled Trial (RCT)

A randomized controlled trial is a scientific procedure commonly used in testing medicines, but also used to test psychological interventions (such as hypnosis or psychotherapy). They are considered to be one of the most reliable ways to collect this kind of scientific evidence. Participants in an RCT are assigned to groups at random - e.g. in a medical trial patients would be randomized to received either a drug or a placebo. It is important that patients are randomly allocated, otherwise their knowledge and expectations about the drug (or placebo) they are receiving can affect the result. The choice of a suitable placebo in psychotherapy trials is the matter of some debate, but ultimately it is not considered a barrier to doing this kind of study.
The Wikipedia entry contains more detail about RCTs.

Suggestion

A communication, conveyed verbally by the hypnotist, that directs the subject's imagination in such a way as to elicit intended alterations in sensations, perceptions, feelings, thoughts and behaviour. Suggestions differ from everyday kinds of instructions in that they imply that a 'successful' response is experienced by the subject as having a quality of involuntariness or effortlessness (British Psychological Society, 2001).

Suggestibility

A measure of responsiveness to suggestion. Typically, in a test situation, a number of suggestions are given (to an individual or a group) and responses are measured. Participants 'pass' an item if they make an appropriate objective response, and subjective responses can also be assessed. Tests of suggestibility can be delivered before a hypnotic induction (in which case they would be considered a test of 'non-hypnotic [or waking] suggestibility) or after a hypnotic induction in which case the test would be considered a measure of hypnotic suggestibility (suggestibility in a hypnotic context). Hypnotic suggestibility is often referred to as 'hypnotizability', although Kirsch & Braffman (2001) has argued that hypnotizability should be operationalised as the difference between scores of hypnotic and waking suggestibility (i.e. hypnotizability = [hypnotic suggestibility] - [waking suggestibility])

Trance

A term used to describe the 'state' that hypnotised people are in following a hypnotic induction. It is more of a descriptive term rather than one offering any real explanatory power - researchers have so far failed to find a unique marker of this trance state. It does fit well with ideas about daydreaming and meditation being similar trance states though.