Hypnosis research

As well as being a mechanism by which psychological processes and phenomenon can be explored, hypnosis is interesting in its own right. These two avenues of inquiry have been formalized as 'instrumental' and 'intrinsic' forms of hypnosis research respectively (Reyher, 1962; Barnier & McConkey, 2003).

In the recent literature hypnosis has been seen to explore a wide range of phenomenon including:

Memory (Barnier, 2002; Cox & Barnier, 2003)
Visual Stroop effects (Raz et al, 2002; Egner et al, 2005)
Auditory hallucinations (Szechtman et al, 1998)
Colour processing (Kosslyn et al, 2000)
Pain (Rainville et al, 1997; Derbyshire et al, 2004)
Voluntary motor control (Halligan et al, 2000; Blakemore et al, 2003)

The use of hypnosis as a tool in research has recently been reviewed by Oakley (2006) who concludes that hypnosis and hypnotic suggestion is a powerful way in which to study psychological phenomena in a controlled way, and that hypnotic phenomena are experienced as subjectively 'real' events accompanied by significant brain changes.

Demand characteristics

One key issue in psychological research is that of demand characteristics. Martin Orne, a hypnosis researcher, suggested that most participants in research strive to be 'good subjects' and wish the experiment to be a success (Orne, 1962). Orne realised that this state of affairs, motivated by participants beliefs, expectations and intentions could lead to systematic error which would severely hamper the interpretability of any data collected. One method to counter this, particularly favoured by social psychologists, was to use deceptive paradigms in order to minimise participants awareness of the research hypothesis and therefore remove one source of systematic bias.

Demand characteristics can present a particular problem for much hypnosis research. In hypnosis research deception can be difficult, since the true nature of the experiment is often directly communicated by the suggestion used (e.g. the demands of a 'pain relief' experiment are clearly communicated by suggestions for pain relief).

Orne developed methodologies which allowed investigators to gauge the demands of an experimental situation. Particularly useful was his real-simulator design, whereby experimental participants of low hypnotic susceptibility were tested by an experimenter blind to their level of hypnotic susceptibility. The low hypnotisables, but not the high hypnotisables, were told to act as if they were high hypnotisables. Additionally, the simulators are told that the experimenter will terminate the study if he suspected simulation. The logic of the real-simulator paradigm indicates that any differences between the performance of the reals and the simulators can be attributed to the differences in hypnotic susceptibility (a genuine effect), whereas if the results are identical then experimental demands cannot be ruled out as a critical factor.

An alternative way to determine whether suggested effects are genuine or the product of bias is to use an objective way of measuring the effect, rather than just relying on subjective report (which is considered vulnerable to bias). Some studies investigate investigate automatic procession which is less vulnerable to conscious bias (see section on attention / conflict), and some of the most interesting studies in recent years have used functional neuroimaging techniques (e.g. ERP, PET, fMRI) which provide measures of brain activity.