Demand characteristics in psychological research

One key issue in psychological research is that of demand characteristics. Martin Orne, a hypnosis researcher, suggested that most participants in experiments strive to be 'good subjects' and wish the experiment to be a success (Orne, 1962). Orne realised that this striving, 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 experimental paradigms that misled participants about the true purpose of an experiment. This was designed to minimise participants awareness of the true 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. For example, the demands of a 'pain relief' experiment are clearly communicated by suggestions given 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 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 is designed such that that any differences between the performance of the reals and the simulators can be attributed to true 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. This avoids relying on subjective report which is considered more vulnerable to bias. Some studies investigate investigate automatic processing 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 that are independent of subjective report.


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