Let’s explore the proposed mechanisms in hypnosis as I wander through the subject this week.
According to some researchers, response expectancies, or ‘the expectation of one’s own non-volitional reactions to situational cues’ are thought to play a major part in both hypnosis and placebo responding. Let’s translate that: a person’s belief that they will respond to something may lead to them actually responding. Possibly the original ‘mind over matter’!
Both hypnosis and placebo (or meaning response – see Dan Moerman for more details on this!) are complex effects that are not yet really understood, except to confound most RCT’s and to provide food for thought for philosophers and psychologists and lay people alike. In this paper, response expectancies were experimentally examined to see whether they have a mediating effect on the effect of ‘suggested’ or placebo analgesia. The methodology is a wonderful design developed by Barron & Kenny, where separate sets of mediator analyses are performed in which the no-treatment control condition is contrasted in turn with each of the treatments. Performing the analyses in this way isolates the mediator function of response expectancies in each treatment. Three regression equations were estimated, to in turn, identify the strength of the relationship between each variable. For more of the maths, go to this paper!
What did they do?
A group of students were recruited to take part in a study examining the effectivenes of ‘an experimental topical anaesthetic’. They were not informed initially that hypnosis was part of the study, to minimise the chance that they would inadvertently over-report their levels of pain to ‘give room’ to pain reduction with hypnosis.
Pain intensity was measured using an 11 point graphical scale 0 = no pain, 10 = pain as intense as one can imagine, and taken every 20 seconds while their finger was put in a pain stimulator for one minute (cruel people these psychology professors!).
Pain expectancy was measured using the same 11 point scale and the score was taken immediately after the baseline pain rating and indicated the level of pain the participants expected to be like if they put their finger in the device without any intervention. During the experiment, participants were asked to use this rating immediately after they had experienced a pain control intervention (but without putting a finger in the stimulator) indicating what participants expected the pain would be like while using the pain intervention they had just experienced.
The Carleton University Responsiveness to Suggestion Scale (CURSS) was used to establish how how much each participant responded to suggestions contained in the scale. This is a measure of three types of suggestability: ‘Objective suggestibility’ : what participants think an observer would have seen them do in response to each suggestion.
‘Subjective suggestibility’ : indicates participants’ internal experience of each suggestion.
‘Involuntariness’: assesses the extent to which participants experienced each suggestion as occurring automatically and without a feeling of effort.
The torture instrument? This was A Forgione-Barber Strain Gauge Pain Stimulator. Details shall remain secret, suffice to say that it squashes the fingertip so that it hurts (ouch! remind me not to be a psychology student).
There were two phases to the experiment: the preparation phase, during which participants were given information about pain management, and offered the chance to try a pain intervention without actually submitting to the finger device. They were then asked to rate what they thought the pain would have been like had they actually had the device applied to their finger while using that coping strategy.
During the intervention phase, participants were administered the intervention while actually submitting to the pain device, and making intensity ratings.
Hypnotic analgesia – in the preparation phase, the participants listened to a tape recording presenting information about hypnosis (correcting myths), using the actual hypnotic induction from the CURSS, information about hypnotic analgesia, and an opportunity to experience a short ‘glove anaesthesia’. In the intervention phase, participants had the same glove anaesthesia hypnosis, but actually got the pain.
In the ‘imaginative analgesia’ condition, participants experienced the same glove analgesia suggestion used in the hypnotic analgesia condition, but without the hypnotic induction or information designed to correct misconceptions about hypnosis. The glove anaesthesia was represented as a ‘guided imagery’. In the preparation phase, participants were asked to ‘use your imagination’ to experience the glove analgesia, while in the intervention phase, the induction was given ‘live’, and you guessed it, the pain was live too.
The placebo condition involved an inert solution presented as an experimental, local, topical anaesthetic, but was actually oil of thyme, and iodine, presented in a brown bottle and labelled ‘Trivaricaine: Approved for Research Purposes Only’. During the preparation phase, participants were told about the effects of analgesia, with a lot of showmanship to demonstrate how ‘powerful’ the liquid was. During the intervention phase, participants had this liquid applied, received the pain, and rated their pain.
The final group were given a ‘no treatment’ condition – They waited the same length of time between the initial rating of pain expectancy as the other three groups, then received the same pain, and asked to re-rate their pain.
I won’t detail the rest of the methodology, but it followed a random assignment format to the four conditions, with equal numbers of males and females to each condition. Strategies were undertaken to minimise the potential for demand bias, ‘hold-back’ effect, and of course, participants were free to withdraw if they chose to.
As usual, I’m not going to go through all the statistical detail – it’s well-documented in the paper, and you should read it if you want to really scrutinise the quality of this study.
As hoped, there was an effect from giving people pain, and the scores differed depending on the pain interventions given – scores did change, with the no-treatment group reporting more intense pain than those in the placebo group, and those in either of the hypnotic groups.
The object of this experiment, however, wasn’t to establish whether hypnosis had an effect – it was to examine the effect of expectancy on pain intensity, and to look at suggestibility.
First up, suggestibility – ‘subjective and involuntariness dimensions of hypnotic suggestibility moderated the effect of the hypnotic analgesia treatment’ – what this means is that aspects of suggestibility do influence how effective hypnotic analgesia can be.
Then expectancies: ‘the effect of each of the three treatment conditions on pain intensity was partially mediated by response expectancies. The extent of mediation by response expectancies appeared to be greater in the placebo condition than in the hypnotic and imaginative analgesia conditions.’
What does this mean? The expectation that pain will be reduced influenced each of the treatment implemented – and more so on the placebo treatment.
Now that’s interesting!
Something about the beliefs that people place on not just the ‘active ingredients’ but the showmanship, ritual, and ‘hype’ involved in a treatment has an effect on how much pain relief a person achieves. Doesn’t that make you think about advertising for pharmaceuticals, the interpersonal skills involved in treatment – and how careful we need to be when discussing treatment options. However well-intentioned, I don’t think we can realistically offer impartial advice on different treatment options because we’re human – so how can a patient not be influenced by our (inadvertent) enthusiasm?
Milling, L. (2009). Response expectancies: a psychological mechanism of suggested and placebo analgesia Contemporary Hypnosis, 26 (2), 93-110 DOI: 10.1002/ch.379