June Research Snippet: Eysenck’s Typology of Hypnotic Suggestion

Okay, research snippet time and it’s back into the past again for a look at an important historical piece of research. Many of you will be familiar with the name of Hans Eysenck (1916-1997). He was allegedly the most widely-referenced psychologist in scientific literature at one point during his lifetime and a pioneer of behaviour therapy. Well, hypnotherapists may not know that Eysenck also carried out some seminal research on the different factors in suggestion and the relationship between hypnosis and personality traits. His original research on hypnosis was published in a well-known journal article and reviewed in his book Dimensions of Personality (1947) which contains a whole chapter on hypnosis and suggestion.

Basically, Eysenck’s research is important for two reasons,

1. He provided data which contradicted the traditional assumption that “hysterical” patients were particularly hyper-suggestibile, i.e., that hypnosis itself is a form of “artificial hysteria.”
2. He was one of the first people to provide evidence which suggested a distinction between different species of suggestion and suggestibility.

Eysenck carried out a series of studies, and reviewed other research. He collated data from over a thousand military personnel and psychiatric patients. Essentially, he found that so-called “hysterics” were no more hypnotisable than other emotionally disturbed patients. However, he did find data pointing to a link between trait neuroticism and hypnotic suggestibility. In the preface to the 1998 edition of the book, presumably written just before his death, he neatly sums up his findings on suggestion,

I was trying to extend my experimental approach to psychiatric concepts, and chose certain specific statements from psychiatric textbooks for testing. It had been almost universally claimed that hysterics are suggestible, but there was no experimental evidence. I applied a number of standard tests of suggestibility to groups of hysteria and anxiety states, as well as non-neurotic controls, and found that there were at least two kinds of suggestibility which I called “primary” and “secondary”. Hysterics did not differ from anxiety states, but neurotics as a group differed profoundly from normals, being much more suggestible. When I showed the results to Sir Aubrey Lewis, my boss, he immediately summoned all the patients I had tested to make sure the hysteria had been correctly diagnosed – he agreed that they had.

Eysenck’s factor analysis of the data from hypnotic suggestion tests seemed to show that indirect (“secondary”) suggestion functioned by means of a fundamentally different mechanism from direct (“primary”) suggestion. Indeed, Eysenck concluded that indirect suggestibility was probably not a single trait and probably not directly related to hypnotism as traditionally understood. He was not alone in this conclusion as earlier researchers such as Binet and Hull had produced similar findings.

In two factorial studies of altogether 16 different tests of suggestibility, it was shown that these tests define two entirely different and separate types of suggestibility: (1) Primary suggestibility, characterised by dependence on ideo-motor action, and (2) Secondary suggestibility, characterised by dependence on indirection. Primary suggestibility was shown to be closely related to hypnosis; secondary suggestibility showed no such relation. (Eysenck, 1947: 201)

If Eysenck’s interpretation of the data is correct then, to put it in plain English, the concept of “indirect hypnosis” becomes a bit of a problem because what we know about traditional hypnotism probably can’t be applied to the use of indirect suggestion. For instance, there’s good evidence that direct (“primary”) suggestibility tends to increase (albeit by a modest amount on average) following a standard hypnotic eye-fixation induction. It wouldn’t follow from this, though, that indirect suggestions would become stronger following the same induction. Moreover, Hull and others had found evidence that direct (primary) suggestion responses tend to increase with practice whereas responses to indirect (secondary) suggestion do not seem to do so, and may even weaken with repetition.

Of course, questions have been raised in the past over the relatioship between Milton Erickson’s indirect approach and traditional hypnotherapy. Eysenck’s analysis is part of the backdrop to that riddle and his intelligent discussion of the research evidence provides some interesting facts and figures to chew over.

You can read a more detailed discussion of this research on my blog article below,

http://ukhypnosis.wordpress.com/2009/05/30/types-of-hypnotic-suggestion-eysenck/

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