Journal of AbnormalPsychology Cog~ight 1985 by the AmericanPsychological AssoOafion, Inc. 1985, Vol. 94, No. 3, 264-271 0021-843X/85/$00.75 Hypnosis as a Retrieval Cue in Posthypnotic Amnesia John E Kihlstrom Heather A. Brenneman University of Wisconsin--Madison University of Saskatchewan. Donna D. Pistole and Ronald E. Shor University of New Hampshire The effectiveness of hypnosis as a retrieval cue was tested in a group of 80 highly hypnotizable subjects who demonstrated posthypnotic amnesia on an initial recall test. The 40 subjects who received a reinduction of hypnosis showed a significant improvement in memory on a retest; there was a significant loss of memory on a third test following termination of the second hypnosis and a more substantial recovery on a fourth test following administration of a prearranged reversibility cue. Another 40 subjects, who merely relaxed before the second test, showed a similar improvement in memory on the retest but no subsequent memory loss. The amount of trial-to-trial improvement in memory shown by the subjects was unaffected by explicit instructions to maintain amnesia until the reversibility cue had been given. Posthypnotic amnesia is not a case of state-dependent retention, nor does hypnosis provide retrieval cues that can lead to the emergence of previously unrecalled memories. Upon termination of hypnosis, many hyp- gard, 1966; Kihlstrom, 1977, 1985). One way notizable subjects find it difficult to remember of approaching the question of mechanism is the events and experiences that transpired to find ways of restoring access to the forgotten while they were hypnotized. The amnesia memories without administering the revers- occurs only as a result of suggestion, and ibility cue. For example, response to amnesia memory for these experiences is restored suggestions is typically tested by the method following administration of a reversibility cue of free recall, as in the Stanford Hypnotic arranged at the time that the suggestion is Susceptibility Scales (Cooper, 1979). Accord- offered by the hypnotist. The phenomenon ing to most theoretical analyses of memory of reversibility marks posthypnotic amnesia retrieval, free recall provides relatively little as a disruption of memory retrieval, rather cue information to the subject. Thus, retrieval than of encoding or storage, in such a way should be improved by cued-recall or recog- that available memories are temporarily ren- nition procedures, which provide more infor- dered inaccessible. mative retrieval cues and thus facilitate access These observations are largely noncontro- .to the material covered by the amnesia. In versial, but there is considerable theoretical fact, subjects typically display less amnesia disagreement with respect to the processes when tested by recognition as opposed to underlying the amnesia phenomenon (Hil- free-recall procedures (Barber & Calverley, 1966; Kihlstrom & Shot, 1978; St. Jean & Coe, 1981; WiUiamsen, Johnson, & Eriksen, This research was supported in part by Grant MH- 1965), although the amnesia is not always 35856 from the National Institute of Mental Health. thereby abolished, especially among the most We thank Eric Eich, Sharon L. Greene, William highly hypnotizable subjects. Such experi- Heindel, Irene P. Hoyt, Ernest E Mross, Margie R. ments support the notion that posthypnotic Solovay, Patricia A. Register, Paula M. Neidenthal, Jeanne Sumi, and Leanne Wilson for assistance in conducting amnesia reflects a disruption in memory the experiment and comments during the preparation of retrieval processes (Kihlstrom, 1985; Kihl- the manuscript. strom & Evans, 1979). Ronald E. Shor died on January 26, 1982. A second line of investigation involves Requests for reprints should be sent to John E Kihl- strom, Department of Psychology,University of Wisconsin, varying the situational demands of the am- W. J. Brogden Psychology Building, 1202 West Johnson nesia test procedure in an effort to breach Street, Madison, Wisconsin 53706. the amnesia. In one experiment, for example, 264 HYPNOSIS AS A RETRIEVAL CUE 265 subjects were tested twice while the amnesia memory is determined by the degree of sim- suggestion was in effect. The first test was a ilarity between the features of the event en- standard test of free recall. For the second coded at the time it occurred and the cue test, subjects received instructions for extra information supplied by the retrieval query. effort in recall, honesty in reporting, or serial Modern research, however, casts doubt on organization; a control group received a sim- the status of posthypnotic amnesia as an ple retest, without any other instructions. instance of state-dependent retrieval (SDR). Subjects of moderate to high hypnotizability For example, amnesia is rarely observed un- in all conditions showed equivalent increases less it is explicitly suggested (Hilgard & in recall from the first test to the second Cooper, 1965), and suggested amnesia can be (Kihlstrom, Evans, Orne, & Orne, 1980). reversed by the administration of a prear- Subsequent research, however, indicated that ranged reversibility cue, without the reinduc- insertion of a putative lie detector or strong tion of hypnosis (Kihlstrom & Evans, 1976; honesty demands does result in an increase Nace, Orne, & Hammer, 1974). The few in recall, compared with control subjects' cases of apparently spontaneous or nonre- recall, for hypnotizable, amnesic subjects who versible amnesia appear to represent the ef- reported that their memory reports were un- fects of expectation or subtle suggestion der voluntary control No differential effect (Young & Cooper, 1972), extremes of the was observed for subjects who reported that distribution of normal forgetting (Cooper, their amnesia occurred involuntarily (Howard 1979), or some other form of pseudoamnesia & Coe, 1980; Schuyler & Coe, 1981). These (Kihlstrom & Evans, 1976). Moreover, sug- results suggest that for some (but not all) gested amnesia can be observed even before subjects, posthypnotic amnesia reflects a vol- hypnosis has been terminated (e.g., Spanos untary suppression of memory reports rather & Bodorik, 1977). than a failure of memory retrieval (Coe, For these reasons, posthypnotic amnesia 1978; Spanos & Radtke-Bodorik, 1980). does not fit the classic pattern of SDR. Nev- In light of these analyses, it is interesting ertheless, the encoding specificity principle to recall the assertions of early authorities on implies that the reinduction of hypnosis, hypnosis that posthypnotic amnesia occurs without administration of the reversibility spontaneously after the termination of hyp- cue, may permit recovery of memories that nosis and persists until hypnosis is reinduced have been forgotten as a result of the amnesia (for a review, see Bramwell, 1913). In these suggestion. Whatever changes in mental or terms, then, posthypnotic amnesia appears physiological state are experienced by a hyp- to have been construed as a form of state- notized subject necessarily constitute features dependent retrieval. This phenomenon was of the organismic context in which hypnotic originally documented in nonhuman animals events take place and may be encoded along (Overton, 1968) and has been observed in with representations of these events. Accord- human subjects following the administration ingly, reinstatement of the hypnotic context of a variety of centrally acting drugs (for may provide retrieval cues that are missing reviews, see Eich, 1977, 1980), as well as when the subject is queried in the normal following shifts in emotional mood (Bower, waking state. This enhanced congruence be- 1981) and sleep state (Evans, 1979). In ad- tween encoding and retrieval conditions, in dition, an analogous effect has been observed turn, might enhance recall. The purpose of following shifts in environmental context (e.g., this experiment was to explore the possibility Smith, Glenberg, & Bjork, 1978). In all these that hypnosis could serve as a retrieval cue cases, the memorability of an event is con- that would be effective in breaching posthyp- trolled by the congruence between the organ- notic amnesia. ismic state or context in which the memory was encoded and that in which retrieval is Method attempted. From a theoretical point of view, Although the present experiment was largely inspired state-dependent retrieval reflects the encoding by the literature on SDR and the encoding specificity specificity principle (Tulving & Thomson, principle, the phenomenon of amnesia is not itselfan 1973), which states that the accessibility of a instance of SDR. Therefore, the classic 2 × 2 design for 266 KIHLSTROM, BRENNEMAN, PISTOLE, AND SHOR SDR experiments---in which the presence of some organ- initial posthypnotic amnesia (recalling 0-3 items on the ismic state is varied orthogonally at both encoding and initial memory test) were retained for the experiment. retrieval--was deemed inappropriate. Instead, posthyp- Out of 211 subjects who received the SHSS:C, 134 met notic amnesia was induced as usual by means of a the criterion of high hypnotizability; data collection was suggestion that included a reversibility cue. After testing discontinued as soon as 80 of these met the criterion of the subject's initial level of response to the suggestion, initial posthypnotic amnesia. These 80 subjects were hypnosis was reinduced and memory was retested. Mem- randomly assigned to one of four conditions in a 2 × 2 ory was assessed for a third time following the termination design, until 20 subjects had been run in