The psychology of suggestion and heightened suggestibility
Hypnosis is associated with profound changes in conscious thought, experience and behaviour and has a long clinical and experimental history. Data on the nature and role of hypnotic induction procedures is still somewhat lacking however, and probably the only thing one can say about them with any conviction is that they enhance suggestibility in some cases. Nevertheless, a review and re-analyses of previous work reveals that the effect of the induction of hypnosis on suggestibility may be substantial, comparable to psychological treatments in general. The work reported here makes a clear distinction between the hypothetical 'hypnotic state' and the phenomena produced by suggestion and aimed to investigate the necessity for the former in producing suggestibility changes and the mechanisms by which both exert their influence. As it had important implications for how non-hypnotic and hypnotic suggestibility were measured in the thesis, Study 1 (n=312) examined the relationship between lateral asymmetry and bodily response to suggestion. Study 2 (n=102) and Study 3 (n=105) explored the notion that absorption and reduced critical thought are instrumental in how inductions effect responses to test-suggestions and suggestions for pain modulation respectively. Study 4 (n=105) investigated the effect on suggestibility of a hypnotic induction and the extent to which the magnitude of this effect is altered by labelling the procedure 'hypnosis'. Study 5 (n=105) examined the influence of compliance to requests on suggestibility and addressed the role of strategy selection in response to suggestions. The findings are important for both clinical and experimental applications and indicate that important determinants of subsequent responses to suggestion are: (i) the definition of the situation as hypnotic which in turn enhances the expectation of benefits (ii) the focussing of attention and the reduction of critical thought and (iii) the facilitation of engaging in goal-directed behaviours through compliance to requests.