Hypnosis and memory, effort, dissociation, and frontal executive functioning

Abstract

Four studies were conducted in an effort to evaluate the relative merits of three different hypotheses concerning the cognitive processes underlying suggested hypnotic amnesia: the sociocognitive view of Spanos and his colleagues (Spanos, 1986), the dissociated experience hypothesis forwarded by Kihlstrom (Kihlstrom, 1984; 1992), and the dissociated control hypothesis forwarded by Woody and Bowers (1994). These hypotheses were evaluated in three studies by means of a selective amnesia suggestion in the recall organization paradigm. In the first two studies hart rate was used as a nonsubjective measure of cognitive effort in order to explore their relationship between hypnosis, hypnotic ability and task-relevant thoughts and imagery on the one hand and cognitive effort on the other. The first study was designed to determine if trying to forget the target material in a task-motivated way would indeed result in a significant heart rate increase compared to simply anticipating the onset of the amnesia trial. Participants unselected for hypnotic ability were administered instruction for relaxation and then asked to learn a categorized word list. After learning the word list to criterion, participants in the experimental condition were given task-motivation instructions to try to forget some of the words whereas participants in the control condition received instructions to simply wait for a subsequent recall trial. Participants given task-motivated instructions showed an increase in heart rate during the subsequent waiting period over and above that observed for participants who received instructions to simply wait for the subsequent recall trial. Thus, heart rate appeared to be a potentially useful independent measure of cognitive effort in this context.

In the second study, high and low hypnotically susceptible participants were administered an hypnotic induction followed by a suggestion for selective amnesia. Once again, heart rate appeared to be a useful independent measure of cognitive effort in this context and according to the cardiac index, it appeared that participants with high hypnotic ability were working no harder to enact the suggestion than were participants with low hypnotic ability, although they were much more successful in doing so.

Study Three was designed to compare the effects of a standard suggestion for selective amnesia with the effects of a distraction task which effectively prevented task-relevant thoughts and imagery (i.e. selective rehearsal) during the waiting period. Participants who were prevented from engaging in task relevant thoughts and imagery by the distraction task were just as amnesic as participants who received a standard suggestion for amnesia, a result which poses a serious threat tot he view (Spanos, 1986; Kihlstrom, 1992) that the presence or absence of task-relevant thoughts or imagery is an important determinant of hypnotic responding.

Finally, Study Four was designed to explore the performance of participants with high and low hypnotic ability on a variety of memory tasks thought to be sensitive to frontal lobe functioning. Results were generally consistent with the view that there may be some interesting memory effects both within and outside of the context of hypnosis for participants with high hypnotic ability.

Results across studies were generally more supportive of the dissociated control theory of hypnotic responding proposed by Woody and Bowers (1994) than either the sociocognitive theory proposed by Spanos (1986) or the dissociated experience theory of Kihlstrom (1992). Theoretical implications are discussed.