Does the more vivid imagery of high hypnotizables depend on greater cognitive effort? A test of dissociation and social-cognitive theories of hypnosis.

In an investigation of the role of cognitive effort in hypnotic responding, high and low hypnotizable participants produced emotionally neutral imagery in response to effortful versus effortless hypnotic suggestions. Heart-rate increase served as an objective index of cognitive effort, and subjective ratings of imagery vividness, absorption, effort, and control were collected. Compared to lows, high hypnotizable participants experienced their imagery as more vivid and absorbing, yet their heart rates indicated no higher level of cognitive effort than lows. Compared to effortless wording, effortful wording of suggestions increased cognitive effort in lows, as indexed by heart-rate increase, but had no effect on the effort expended by highs. Ratings of subjective control were strongly correlated with subjective effort for lows but unrelated for highs. These results support the dissociated-control theory of hypnosis rather than the dissociated-experience or social-cognitive theories.