Selective Hypnotic Amnesia: Is it a Successful Attempt to Forget
or an Unsuccessful Attempt to Remember?
Selective Hypnotic Amnesia: Is it a Successful Attempt to Forget
or an Unsuccessful Attempt to Remember?
This article is based in part on a doctoral dissertation submitted by Thomas M. Davidson (1986). Portions of this article were previously presented at the annual conventions of the Society for Clinical and Experimental Hypnosis, Indianapolis, October 1982, and Boston, October 1983. Preparation of this article was supported in part by a Social Sciences and Humanities Research Council (SSHRC) of Canada Doctoral Fellowship awarded to Thomas A. Davidson and by an SSHRC grant awarded to Kenneth S. Bowers.
We thank the Waterloo Hypnosis Research team for conducting hypnotic ability prescreening sessions and in offering assistance throughout. Thanks are due to Claude Balthazard, Kathy Belicki, Patricia Bowers, Deborah Chansonneauve, Jane Dywan, Paul Kelly, Kevin Parker, and Eric Rothmar. Rod Martin, Joy Fisher, and Sandra Van der Meulen acted as raters for the interviews. Neil Charness, Daniel Schacter, Bernard Suits, and Erik Woody offered specific criticisms and suggestions as members of the dissertation committee.
Suggested hypnotic amnesia is one of the most closely studied topics in hypnosis (e.g., Kihlstrom, 1977; Kihlstrom & Evans, 1979). Typically, it is produced by hypnotized subjects who are administered suggestions that they will be unable to recall specific information until the administration of a prearranged cue. Amnesic subjects are subsequently unable to recall this information when challenged to do so. When the cancellation cue is provided, however, the information is easily retrieved.
According to one view, suggested amnesia is achieved when persons actively disattend retrieval cues that otherwise engender recall of previously learned material (Spanos, 1986; Spanos & Radtke, 1982). This inattention hypothesis of hypnotic amnesia (e.g., Spanos, Radtke, & Bertrand, 1985; Spanos, Radtke, & Dubreuil, 1982; Spanos, Radtke-Bodorik, & Stam, 1980) is firmly tied to the concept of encoding specificity (Tulving & Thomson, 1973). Encoding specificity proposes that the amount of information remembered depends on the degree to which retrieval cues at recall match the cues present during initial learning (encoding) of the target material. According to this view, hypnotic amnesia results from inattention to various memory cues that otherwise aid recall. Specifically, when hypnotic subjects shift their attentional focus away from the task of list recall, the content of the information to which they are not attending is unlikely to match the information contained in the memory traces of the target events. Retrieval is therefore inefficient. When presented with the cancellation cue, subjects simply refocus attention to the retrieval cues that were present during encoding and the target material immediately comes to mind. (Spanos, Radtke, & Dubreuil, 1982, p. 565 [emphasis added])
In other words, the principle of encoding specificity, here endorsed by Spanos, Radtke, and Dubreuil (1982), argues that when salient cues present during learning trials are later present during attempts at retrieval, they serve as a powerful mnemonic to aid recall. Accordingly, one way of achieving hypnotically suggested amnesia is to deliberately disattend such powerful mnemonic cues.
Most studies put forward in support of this disattention hypothesis have used the recall-organization paradigm. Several steps are typically involved: (a) Preliminary experimental treatments are administered (e.g., hypnotic induction or task-motivating instructions); (b) subjects learn to criterion a categorized word list on independently randomized free-recall trials (learning trials); (c) an amnesia suggestion is given for all of the words just learned; (d) subjects are then challenged to recall the list (amnesia trial); (e) the amnesia suggestion is canceled; and (f) subjects are asked a final time to recall the words (recovery trial).
The degree of categorical organization in subjects' recall on the last learning trial and on the amnesia and recovery trials provides the key to understanding the cognitive processes involved in hypnotic amnesia. Typically, subjects who learn a list of words drawn from several taxonomic categories (e.g., alcoholic beverages, birds, and flowers) organize their recall by categories inferred from the list, regardless of the original order of word presentation (Kausler, 1974). In maximally organized recall, all of the words in one category are recalled and are followed by all of the words in the next category, and so on until the list is recalled completely. Conversely, recall is disorganized to the extent that words from different categories are recalled in a mixed-up order. Only those subjects who recall a sufficient number of words on the amnesia trial to permit computation of organization scores can be included in the data analysis. These studies have therefore been restricted to the investigation of partial amnesia.
The recall organization paradigm has produced three consistent findings. First, partial amnesia is accompanied by recall disorganization (Radtke-Bodorik, Planas, & Spanos, 1980; Radtke-Bodorik, Spanos, & Haddad, 1979; Spanos & Bodorik, 1977; Spanos & D'Eon, 1980; Spanos, Radtke, Bertrand, Addie, & Drummond, 1982; Spanos, Radtke-Bodorik, & Stam, 1980; Spanos, Stam, D'Eon, Pawlak, & Radtke-Bodorik, 1980). In relation to the last learning and recovery trials, partial amnesiacs evidence greater disorganization on amnesia trial recall than do nonamnesiacs. Second, the relationship between recall disorganization and partial amnesia is mediated by hypnotic ability (Spanos, Radtke-Bodorik, & Stam, 1980, p. 11). In other words, highly susceptible subjects with disorganized recall on the amnesia trial were more likely to be partially amnesic than were low susceptible subjects with disorganized recall. Third, the disorganization effect is not evident in the recall of subjects instructed to fake amnesia (Spanos, Radtke, Bertrand et al., 1982; Spanos, Radtke-Bodorik, & Stam, 1980), so it does not appear to be a response to demand characteristics.
According to the disattention hypothesis, the most important cues available during initial learning are the organizational features of the word list. During the amnesia trial, subjects ought to recall words targeted for amnesia easily if they focus attention on those retrieval (organizational) cues that were present during initial learning. This prediction follows from the concept of encoding specificity. However, subjects may instead focus attention on things unrelated to the task of recall (e.g., the physical sensations of relaxation, mental imagery, or distracting thoughts). Such self-distracting subjects do not expose themselves to the organizational cues that facilitated learning of the words in the first place; total or partial amnesia is the consequence. Words that partial amnesiacs do manage to remember presumably have a number of accidental features (high word salience or primacy effects) that increase the probability of their being recalled (Stam, Radtke-Bodorik, & Spanos, 1980).
The disattention hypothesis appears consistent with the results of experiments that have required subjects to be amnesic for entire word lists. However, our studies evaluate this hypothesis within the context of selective amnesia. Selective amnesia suggestions direct subjects to forget only one circumscribed part of learned material (Evans, 1979), such as a single category of words in a categorized word list.
In our selective-amnesia paradigm, subjects are placed in a conflictful situation. They must attend to retrieval cues in order to recall words not targeted for amnesia; on the other hand, if amnesia is to be successful, attention to these retrieval cues should not engender recall for words that are targeted for amnesia. Organizational features are the most important cues to facilitate the recall of organized word lists (Spanos, Radtke-Bodorik, & Stam, 1980). Consequently, if subjects recall the nontargeted words in an organized fashion, it will constitute clear evidence that they had attended the most salient retrieval cue, namely, the categorical organization of the words. However, the encoding specificity principle implies that organized recall of nontargeted words also acts as a retrieval cue for the targeted words, thereby increasing the probability that targeted words too will be recalled. If, on the other hand, subjects disattend organizational cues in order to forget the words targeted for amnesia, a large proportion of nontargeted words will also be forgotten. As well, words that subjects manage to recall while disattending the organizational cues will also be less well clustered than during pre- and postamnesia trials. In short, organized retrieval of words not targeted for amnesia should, according to the principle of encoding specificity, engender recall for the targeted category of words. On the other hand, disattending the organizational cues originally used to facilitate learning of the word list ought to result in reduced recall of words not targeted for amnesia.
In the selective-amnesia paradigm, the major focus of analysis is the recall and organization of words not targeted for amnesia. Even subjects who are totally amnesic for the targeted category will likely recall at least some nontargeted words on which organization scores can be computed. Thus, unlike the entire list paradigm, this investigation is not restricted to partial amnesia but can include subjects who are completely amnesic for the targeted category. Subjects who best exemplify suggested amnesia can thus be retained for analysis.
According to Spanos and his colleagues, hypnotic amnesia is a result of an active and volitional strategy to forget information targeted for amnesia (Spanos, 1986; Spanos & Radtke, 1982); the resulting amnesia may nevertheless be experienced as occurring nonvolitional. Spanos (1986) regarded reports of nonvolitional forgetting as a misattribution. In part, such a misattribution is due to the ambiguous nature of hypnotic suggestion, which implies that the suggested behavior will happen but not intentionally. By way of contrast, subjects who receive task-motivated instructions (e.g., Barber, 1969) are confronted with unambiguous demands to achieve the instructed effect. Accordingly, these subjects are more likely to correctly attribute their compliant behavior to their own active efforts. Other investigators (e.g., K. S. Bowers, 1981; Weitzenhoffer, 1978) have regarded the experience of nonvolition to be part and parcel of the suggested effect rather than a misattribution.
In our research we used a selective-amnesia paradigm to evaluate the notion that active attempts to forget a specific category of words (e.g., by disattending the organizational features of the word list) is the basis for hypnotically suggested forgetting. As well, we examined the experience of nonvolition that often accompanies suggested forgetting.
Experiment 1 Method Subjects
The subjects were 72 University of Waterloo (Waterloo, Ontario, Canada) undergraduate volunteers (36 women and 36 men), selected on the basis of hypnotic ability from a pool of 257 volunteers. Each subject was prescreened on the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS, Form A; Shor & Orne, 1962) and on a group version of the Stanford Hypnotic Susceptibility Scale, Form C (Weitzenhoffer & Hilgard, 1962), developed at the University of Waterloo and known as the Waterloo-Stanford Scale of Hypnotic Susceptibility, Group C (WSGC). Thus, 24 high (WSGC scores of 9–12), 24 moderate (WSGC scores of 5–8), and 24 low (WSGC scores of 0–4) hypnotizable subjects participated in the study. All subjects were informed that the session might or might not involve hypnosis. They were paid $4.00 (Canadian) for their participation in the experimental session.
Half of the high, moderate, and low hypnotizable subjects were randomly assigned to either a hypnosis or task-motivation condition. Thus, 36 subjects (12 high, 12 moderate, and 12 low hypnotizable) participated in each condition. To encourage low hypnotizable subjects to maximum performance in hypnotic conditions, they were informed at the time of their recruitment that they were specifically selected for the study because hypnotic ability prescreening had revealed that they would be appropriate for use in this experiment (cf. London & Fuhrer, 1961). All subjects were seen individually. The experimenter was unaware of the hypnotic ability of the subjects.
Hypnosis and task-motivation conditions
Hypnotic subjects were first informed that the experiment involved the induction of hypnosis and then administered the eye-closure induction technique from the WSGC. Task-motivation subjects were informed that the session would not involve hypnosis and then given the task-motivation instructions originally presented in Spanos and Bodorik (1977). Next, task-motivation subjects were asked to close their eyes so that they could devote their full concentration to the task and to keep them closed until they were instructed to open them.
After the hypnotic induction or task-motivation instructions, all subjects learned a 16-item, four-category word list. The list was drawn from Battig and Montague's (1969) list of the most frequently cited exemplars of word categories, with four frequently cited mono- or disyllabic, nonalliterative exemplars chosen for each of the four categories. The words in the list were: rum, whiskey, vodka, and beer (alcoholic beverages); robin, parrot, sparrow, and eagle (birds); rose, daisy, orchid, and tulip (flowers); and table, chair, sofa, and bed (furniture). A series of randomized list orders were computer generated, with the restrictions that no two words from the same category nor two words with the same first letter appeared in succession. The subjects were informed that they were to learn a list of words on a series of free-recall trials, that the words were to be presented on an audiotape recorder, and that the words would appear in a different order on each trial. They were further informed that the free-recall trials would continue until they were able to recall all of the words correctly on two consecutive trials. The list was presented aurally at a rate of 2 s per word, and each list presentation was followed by a 60-s recall period.
When subjects in both the hypnosis and task-motivation conditions had learned the words to criterion, they were given a suggestion that they would forget all the words in one of the categories in the list. The category targeted for amnesia was counterbalanced so that each of the four categories was targeted an equal number of times for each level of hypnotic ability in both the hypnosis and task-motivation conditions. Task-motivation and hypnosis subjects received the same amnesia suggestion:
You have attended well to the task and have learned the list of words. In a few moments, I am going to ask you to open your eyes. However, when I do, you will be unable to remember the [category exemplars], or any of the particular [target categories] you have just memorized. You will be unable to remember the [target category] or any of the [category exemplars] until I say “Now you can remember everything.” Until that time, your memory for [target category] will just be blank. However, you will have no sense of having forgotten anything, as if the words you do remember cover up and heal any wounds in your memory—that the words you do recall are sufficient. You will not be able to remember that you have forgotten anything at all.
After the amnesia suggestion, hypnotic subjects were alerted from hypnosis by counting backwards from 20. Task-motivation subjects waited for 20 s and were then told to open their eyes.
Immediately thereafter, subjects were asked to recall the list again and were given 60 s to do so. If the subjects did not report aloud all of the words during this interval, they were asked “Anything else?”, and an additional 20-s recall period was provided. The amnesia trial was followed by the signal to cancel the amnesia, and the subjects were asked to recall the words a final time (the recovery trial).
The subjects received a score of 1 for each targeted word that appeared on the recovery trial but that had not appeared on the amnesia trial. They were classified as total amnesiacs if they obtained an amnesia score of 4. Partial amnesiacs obtained a score of at least 1 but less than 4. Nonamnesiacs obtained an amnesia score of 0.
The degree of recall organization was assessed by the adjusted ratio of clustering (ARC) score derived by Roenker, Thompson, and Brown (1971). The ARC score reflects the proportion of actual category repetitions (i.e., the number of times a category item follows an item from the same category) to the total possible category repetitions above chance in a given protocol. The ARC score is rather insensitive to the number of words recalled. Perfect clustering is set at 1, and chance clustering is set at 0. Separate organization scores were calculated for all of the words recalled by subjects on the last learning trial, on the amnesia trial, and on the recovery trial.
Immediately after the recovery trial, the subjects' experiences were assessed in a postexperimental interview. The interview was based on several paper-and-pencil scales that probe subjects' experiences in response to an amnesia suggestion (Spanos & Bodorik, 1977). The subjects were also asked to describe, as thoroughly as possible, what they had experienced from the time that they were asked to forget the targeted category up to the time they were told that they could remember everything. Later, two judges, unfamiliar with the experimental hypotheses and unaware of the hypnotic ability and treatment condition of the subjects, independently rated the audiotaped interviews of the total and partial amnesiacs. They evaluated the interviews to determine whether failure to recall targeted words on the amnesia trial was due to verbal inhibition of words that were actually recalled and whether amnesia was experienced as volitional or nonvolitional.
Volitional amnesiacs were defined as those subjects who testified that they deliberately and consciously tried to forget the targeted words during the amnesia trial. That is, their experience was one of effortful nonrecall. Nonvolitional amnesiacs were defined as those subjects who described doing nothing effortfully to effect amnesia during the amnesia trial. Nonrecall was for these subjects something that they felt had just happened to them without any experience of effort on their part. Subjects that testified that they remembered the targeted words on the amnesia trial but either chose not to say them or felt unable to say them (e.g., “My jaw became stuck, and I just couldn't speak”) were classified as verbal inhibitors.
Interrater agreement for the verbal-inhibition classification was 100%. For the volitional–nonvolitional distinction, the agreement was 95%. Disagreements were resolved by discussion between the two judges. consistent with previous studies, it was found that amnesia is a difficult hypnotic performance. Overall, only 8 subjects (11%) were totally amnesic, 12 subjects (17%) were partially amnesic, and 47 (65%) were nonamnesic. Five subjects (7%) were identified by the judges as verbal inhibitors. The data from verbal inhibitors are not included in any subsequent analyses.
Learning trials to criterion A 3 (high, moderate, or low hypnotic ability) × 2 (hypnosis vs. task motivation) analysis of variance (ANOVA) was performed on the number of learning trials to criterion. No significant results were obtained from this analysis. A one-way ANOVA was performed on the number of learning trials for total, partial, and non amnesic subjects but yielded no significant differences among the groups. Overall, the average number of learning trials to criterion was 7.09.
A 2 (total vs. partial amnesia) × 4 (word categories) ANOVA determined that there was no main effect for word categories and that word categories did not interact with the extent of amnesia. Therefore, none of the categories used in the experiment were inherently more forgettable when targeted for amnesia. A 3 (high, moderate, or low hypnotic ability) × 2 (hypnosis vs. task motivation) ANOVA was performed on the amnesia scores. Hypnosis and task-motivation subjects did not differ, and the treatments did not interact with hypnotic ability. The only statistically significant result obtained was a main effect for hypnotic ability, F(2, 66) = 7.114, p < .01. High hypnotizable subjects recalled 1.70 more words on the recovery trial than they did on the amnesia trial. The corresponding figures for the moderate and low hypnotizable subjects were 0.73 and 0.21, respectively. Scheffé post hoc comparisons revealed that high hypnotizable subjects were more amnesic for the targeted category than were moderate and low hypnotizable subjects (p < .05) but moderate and low hypnotizable subjects did not differ. The correlation between amnesia scores and hypnotic ability was .31 for the hypnosis subjects, .38 for the task-motivation subjects, and .35 overall. Seventy-five percent of total amnesiacs were high hypnotizable. None of the total amnesiacs were low hypnotizable. Partial and nonamnesiacs represent subjects from all levels of hypnotic ability. Clearly, selective amnesia is most readily accomplished by hypnotically talented subjects.
Organization scores and nontargeted words
The central data analysis in this experiment concerns the numbers of nontargeted words recalled on the amnesia and recovery trials and their organization (ARC) scores. These data, however, could not be legitimately subjected to ANOVA because of the overwhelming uniformity of scores and the resulting violation of the homogeneity of variance assumption. Such an analysis would not be informative in any case. Generally speaking, the recall of nontargeted words and recall organization were virtually perfect.
Judges' volition ratings
Out of the combined group of 8 total and 12 partial amnesiacs, only 1 subject was classified by the judges as a volitional amnesiac. This single volitional subject was moderate hypnotizable and participated in the hypnosis condition. As predicted, the deliberate strategy of nonrecall led this subject to forget 5 out of the 12 nontargeted words and to demonstrate the lowest organization score (.75) on the amnesia trial among the amnesic subjects. In other words, this subject's protocol was characterized by reductions in nontargeted words recalled and by reduced organization.
The critical finding of this experiment concerns the ARC scores and the number of nontargeted words recalled during the amnesia trial. Amnesic subjects forgot targeted words, while they recalled virtually all the nontargeted words with almost perfect recall organization. Evidently, selective forgetting can be successfully accomplished even though subjects use (and therefore attend) powerful mnemonic cues that—according to the principle of encoding specificity—ordinarily facilitate recall of the words targeted for amnesia.
Our study also confirms that selective amnesia is most readily achieved by high hypnotizable subjects. On the other hand, hypnotic procedures did not prove necessary to achieve amnesia; there were no significant differences between the amnesia scores of subjects in the hypnosis and task-motivated conditions. This finding is not consistent with the findings of several previous reports that have compared hypnosis and task-motivation subjects (Radtke-Bodorik, et al., 1980; Radtke-Bodorik et al., 1979; Spanos & Bodorik, 1977; Spanos, Radtke-Bodorik, & Stam, 1980) and found differences in amnesic performance between such groups.
However, our findings are in line with the argument that hypnotic ability may be of greater importance in producing suggested effects than are formal hypnotic procedures (K. S. Bowers & Kelly, 1979). The “receiver characteristics” (K. S. Bowers, 1977, p. 222) of high hypnotizable subjects may be of paramount importance in engendering suggested effects, regardless of whether or not such communications occur after an explicit hypnotic induction. Nevertheless, it still has to be explained why previous investigators have found differences in amnesic performance between their hypnotic and task-motivation groups, whereas our experiment did not.
One explanation for this difference is that selective amnesia may preclude the kind of volitional forgetting that task-motivation subjects typically attempt. Recall that task-motivation subjects were predicted to demonstrate greater incidence of volitional forgetting than the hypnosis group. However, none of the total or partial amnesiacs in the task-motivation group was classified by judges as a volitional amnesiac. This finding contrasts with those reported by Coe and his colleagues (Howard & Coe, 1980; Schuyler & Coe, 1981) who found that even among high hypnotizables subjects who are hypnotized, about half experience amnesia as volitional, and half experience amnesia as nonvolitional. Their evidence further suggests that volitional amnesiacs are more likely to breach amnesia in the face of pressure to do so. Subsequent evidence, though somewhat less clear, also indicates “that voluntary [subjects] are more likely to breach than are involuntary [subjects]” (Schuyler & Coe, 1989, p. 328). Given these results, one can only ask: What became of the volitional forgetters in our experiment?
Perhaps potential volitional amnesiacs in this experiment anticipated that, because of the significant number of nontargeted words (12) to be recalled, efficient recall of these nontargeted words was impossible without attending to the organizational mnemonic. Attending to the organizational mnemonic, on the other hand, might cue the recall of the targeted words. Accordingly, would-be volitional amnesiacs were faced with two possibilities: verbal inhibition or overt breaching of amnesia. In either case they would not count as amnesic subjects. Consequently, volitional amnesiacs are underrepresented in this study. Instead of verbally inhibiting or recalling the items targeted for amnesia, high hypnotizable subjects in the task-motivation group seem to have achieved selective amnesia in the same way as their counterparts in the hypnotic condition.
In sum, the results of Experiment 1 indicate that: (a) subjects did not disattend the organizational mnemonic as a means of achieving selective amnesia; (b) attention to important retrieval (organizational) cues does not necessarily prevent selective amnesia in high hypnotizable subjects; and (c) conscious and volitional attempts to comply with the selective amnesia suggestion proved unsuccessful.
In Experiment 1, we used posthypnotic procedures in which the subjects were alerted from hypnosis before the amnesia trial. The research of Spanos and his colleagues, however, has typically tested for amnesia while subjects were still hypnotized (e.g., Spanos & D'Eon, 1980); indeed, subjects remained hypnotized during all recall trials. It is possible that there are differences between posthypnotic amnesia and amnesia within hypnosis (hypnotic amnesia) that account for the failure of Experiment 1 to show evidence of inattention strategies in suggested amnesia.
Some features of the hypnotic experience may facilitate the use of disattention to produce forgetting. The hypnotized person may benefit in this regard from the presence of physical sensations of relaxation (Spanos & Bodorik, 1977), absorption in task-irrelevant imagery (Tellegen & Atkinson, 1974), and a reduced reality orientation (Shor, 1959). When amnesia is assessed posthypnotically, disattention may be more difficult: The subject is alert and reality-oriented and may have less access to distracting imagery or strong sensations of physical relaxation. In short, a strategy of inattention may explain hypnotic amnesia better than it does posthypnotic amnesia.
Furthermore, posthypnotic procedures require time to alert subjects before the amnesia trial—time that may be necessary for subjects to convert suggestions for amnesia into nonvolitional forgetting. In the hypnotic-amnesia paradigm, however, the interval between administering the amnesia suggestion and the amnesia trial is typically 10 s, which may provide too little time for subjects to recruit an amnesic response.
Experiment 2 addressed these issues directly. The purpose of the experiment was to provide a test of the inattention hypothesis by examining selective amnesia both within hypnosis and posthypnotically. In addition, the interval from the administration of the amnesia suggestion to the amnesia trial was varied for hypnotic subjects in order to determine whether such an interval is important. Finally, we assessed whether subjects who reported volitional amnesia for the items of a standardized scale of hypnotic ability would maintain a similar strategy of forgetting when selective amnesia was required.
The subjects were 50 University of Waterloo undergraduate volunteers (27 women and 23 men), selected on the basis of hypnotic ability from a large pool of volunteers who had been prescreened on the HGSHS, Form A, and the WSGC. To increase the probability that subjects would display amnesia, we chose subjects who were high hypnotizable (WSGC scores of 8–12) and who had also passed the posthypnotic amnesia item on the WSGC. Of these subjects, 40 had reported their amnesia to be nonvolitional, and 10 had reported it to be volitional. These latter 10 subjects were the only high hypnotizable subjects in the entire sample who rated themselves as volitionally amnesic. Volition ratings from the WSGC were adapted from Howard and Coe (1980). All subjects received $4.00 (Canadian) for their participation in the experiment.
All subjects received an hypnotic induction procedure identical to that used in Experiment 1. The learning task also was identical to that in Experiment 1, except that that the word crow was substituted for parrot (the subjects' performance on the learning trials in Experiment 1 suggested that parrot was often misheard on early trials). Experiment 2 was simplified by requiring all subjects to be amnesic for the same category, birds (Experiment 1 indicated that none of the word categories were inherently more difficult or easy to forget). The amnesia suggestion was otherwise identical to that in
Experiment 1.Treatment conditions
The 40 nonvolitional amnesiacs were randomly assigned to one of three conditions. In the hypnosis–immediate condition, the subjects (7 women and 6 men) were given a selective-amnesia suggestion while they were hypnotized. The amnesia trial began 10 s after the administration of the suggestion. The subjects were asked to open their eyes and recall the word list; they were given 60 s to do so. The cancellation cue was then given, and the subjects were asked to recall the words one more time for the recovery trial. They were then asked to close their eyes and were alerted. This is the procedure standardly used by Spanos and his associates, and it is the experimental context within which the inattention hypothesis was initially investigated (e.g., Spanos & D'Eon, 1980).
The hypnosis–delay condition was identical to the hypnosis–immediate condition, except that the subjects (7 women and 6 men) waited for 60 s between the administration of the amnesia suggestion and the amnesia trial. The posthypnosis condition was identical to the procedure used in Experiment 1. The subjects (8 women and 6 men) were alerted after the administration of the amnesia suggestion. The process of alerting the subject was timed so that it would take 60 s. Thus, the length of time between the amnesia suggestion and the amnesia trial was identical for the hypnosis–delay and the posthypnosis groups. A comparison among these three groups permits an examination of whether differences in hypnotic performance are due to the hypnotic or posthypnotic treatment conditions or whether such differences are due to the length of time between the administration of the amnesia suggestion and the subsequent amnesia-trial recall.
A fourth treatment group, the posthypnosis–volitional condition, consisted of the 10 high hypnotizable subjects (5 women and 5 men) who had testified that their forgetting on the screening tests was volitional. Ideally, an equal number of volitional and nonvolitional amnesiacs (as defined by the prescreening test) ought to have been included in each of the other treatment conditions. This was not possible, however, because so few high hypnotizable volitional amnesiacs appeared in the prescreening sample.
The interview followed the procedures of Experiment 1. Two judges who were unfamiliar with the experimental hypotheses and who were unaware of the treatment condition of the subjects independently rated the audiotaped interviews of the total and partial amnesiacs. They identified volitional and nonvolitional amnesiacs and verbal inhibitors according to the criteria described in Experiment 1.
Interrater agreement for the volitional versus nonvolitional classification was 89% for the amnesia trial. The agreement for the verbal-inhibition classification was 98%. Disagreements were resolved by discussion. Only 2 subjects (4%) in the entire sample were nonamnesic. Thirty-three subjects (66%) were totally amnesic, and 12 (24%) were partially amnesic. Three subjects (6%) were identified by the judges as verbal inhibitors. The data from verbal inhibitors and nonamnesiacs were not included in any of the analyses.
The mean hypnotic ability scores for the subjects in the hypnosis–immediate, hypnosis–delay, posthypnosis, and posthypnosis–volitional conditions were 10.58, 10.46, 10.64, and 9.12, respectively. A one-way ANOVA was performed for hypnotic ability in each treatment condition. The results were significant, F(3, 41) = 4.556, p < .01. Scheffé post hoc comparisons revealed that the posthypnosis–volitional group had significantly lower hypnotic ability than did the other three treatment conditions (p < .05) , which did not differ from each other. This outcome is a consequence of the catch-as-catch-can nature of the posthypnosis–volitional group. Caution must therefore be exercised in interpreting any other difference manifested by subjects in this group when they are compared with subjects in the three other conditions. Finally, total and partial amnesiacs did not differ in their hypnotic ability.
Learning trials to criterion
A one-way ANOVA was also performed on the number of learning trials to criterion for each treatment condition. The result was not significant. Likewise, total and partial amnesiacs did not differ in trials to criterion. Overall, the mean number of learning trials to criterion was 5.47.
Organization scores and nontargeted words recalled
As in Experiment 1, there was no general pattern of recall disorganization nor of reduced recall of nontargeted words for treatment conditions or for total versus partial amnesiacs. The mean ARC scores over the last learning, amnesia, and recovery trials for all four treatment conditions were all above .90, and most were above .95 (range, .91–1.00). Clearly, only trivial departures from perfect organization were obtained. This high level of organization remained true when subjects were recategorized into totally and partially amnesic subjects. As well, totally and partially amnesic subjects in all conditions recalled well over 11 nontargeted words during the amnesia and recovery trials (range, 11.38–12).
The selectivity of the amnesia effects implied by these data is presented in Figure 2. The mean numbers of targeted words recalled and the mean numbers of words recalled within each of the three nontargeted categories are plotted for each treatment condition. Figure 2 illustrates that subjects in each condition were able to selectively forget target category words without negatively affecting the recall of nontargeted words.
Judges' volition ratings
Almost all the amnesic subjects (95.6%) were rated as having done nothing volitionally during the amnesia trial to forget the targeted words. Only 2 subjects (4.0%) among the total amnesiacs were classified as volitional forgetters, and both were in the group of partial amnesiacs. One was a member of the posthypnosis group, and 1 was in the posthypnosis–volitional condition. The mean ARC scores for these 2 subjects over the last learning, amnesia, and recovery trials were 1.00, .72, and .79, respectively, and the corresponding mean numbers of nontargeted words recalled over trials were 12, 9.5, 11.5. As in Experiment 1, the rare volitional forgetter demonstrated the kind of reduced recall and organization that is anticipated when active efforts to forget are made.
Because we selected subjects on the basis of both high hypnotic ability and their passing score on the amnesia item of the prescreening hypnotic ability scale, 81% of the sample evidenced either total or partial amnesia. Furthermore, each treatment condition was effective in engendering amnesia, but none was superior to any of the others in this regard. Our data also reveal that the interval from the administration of the amnesia suggestion to the amnesia trial was unrelated to whether or not subjects were totally or partially amnesic. Total and partial amnesiacs were also equally represented on the hypnosis–posthypnosis dimension.
Most important, the results of Experiment 2 indicate that amnesic subjects continued to recall the nontargeted words on all the recall trials successfully and in an organized fashion, regardless of whether the selective amnesia suggestion was enacted hypnotically or posthypnotically. Also, no differences emerged on these measures for subjects who completed amnesia-trial recall immediately after the administration of the amnesia suggestion and those who had a longer waiting period. As was true for Experiment 1, the high degree of organization evident in the recall of amnesic subjects implies that selective forgetting can occur even in the presence of powerful mnemonic cues that ordinarily facilitate recall of the words targeted for amnesia.
Judges' ratings revealed that subjects in this experiment, regardless of their treatment condition, typically did not describe their amnesia as being under direct volitional control. The attempt to maximize the number of volitional amnesiacs by including the posthypnosis–volitional group was not successful. As a group, the subjects who were selected as volitional amnesiacs on the WSGC proved, for the most part, to be nonvolitional amnesiacs on the experimental task. They did not display any reductions in nontargeted words recalled or amnesia-trial disorganization. Why did these subjects shift from being volitional amnesiacs on the WSGC, to nonvolitional amnesiacs on the selective-amnesia task?
As we indicated earlier, perhaps the selective-amnesia paradigm prevents active and volitional efforts to forget words targeted for amnesia. Unlike the entire-list amnesia procedures used by Spanos and his associates (e.g., Spanos & D'Eon, 1980), selective amnesia disallows a strategy of avoiding the entire task of recall; indeed, subjects must attempt to recall at least 75% of the words they had just learned. As demonstrated by the majority of subjects in Experiment 1, the recall of the nontargeted words in an organized fashion itself cues the recall of the targeted words, thus making conscious and deliberate strategies of attention diversion difficult to maintain. The posthypnosis–volitional subjects in this second study were high hypnotizable subjects who had used a conscious strategy of nonrecall in the screening test, which suggests forgetting of recent experiences in their entirety. However, when these subjects faced the difficulties of volitional forgetting in the selective-amnesia task, they were evidently able to achieve amnesia nonvolitionally.
General Discussion Organization and Recall of Nontargeted Words
The data from the two experiments clearly indicate that high hypnotizable subjects may be selectively amnesic for one category of a categorized word list without impairing recall organization or the recall of words not targeted for amnesia. To state it the other way around, selectively amnesic subjects are capable of attending to important cues for retrieval (i.e., the organizational features of the word list) yet are unable to recall material targeted for amnesia.
These results pose difficulties for any model of hypnotic amnesia that regards suggested forgetting as occurring because subjects actively attempt to forget information targeted for amnesia. It is clear that the findings are not consistent with deliberate disattention to the task of recall. If that had happened, the recall and organization of words not targeted for amnesia would have been seriously impaired—and that did not occur. Alternatively, Spanos and his associates have argued that selective amnesia is actively and deliberately achieved, not by disattending organizational cues, but by mentally segregating the words to be forgotten from the remaining words and forgetting the former by selectively rehearsing the latter (Bertrand & Spanos, 1985; Spanos & de Groh, 1984; Spanos et al., 1985). However, this selective rehearsal strategy collides with the principle of encoding specificity, which Spanos, Radtke, and Dubreuil (1982) endorsed (see the earlier quotation). According to this principle, the organized recall (and rehearsal) of words not targeted for amnesia ought to serve as a powerful mnemonic cue that facilitates the recall of words for which the subject is supposed to be selectively amnesic. Why is the principle of encoding specificity abrogated on switching from amnesia for all the words on a list to selective amnesia for only one category of them?
As well, there is a paradox of sorts involved in producing selective amnesia by selective rehearsal. In our experiments, for instance, a deliberate attempt to forget 4 of 16 words required subjects to remember precisely which words to forget in order to avoid rehearsing them. On the other hand, there is no paradox when amnesia for all 16 words is suggested, because the entire task of recall can be avoided—a strategy evidently pursued with some success on the WSGC by the 10 subjects who were selected as volitional forgetters in Experiment 2.
Volitional Versus Nonvolitional Experience
Both experiments revealed that independent judges rated subjects' forgetting as nonvolitional. Experiencing amnesia as nonvolitional was virtually universal, even in task-motivated subjects and in subjects who demonstrated volitional forgetting on prescreening tests. Perhaps selective amnesia effectively prevents volitional strategies of forgetting. Indeed, volitional attempts to divert attention from relevant retrieval cues may jeopardize the successful recall of words not targeted for amnesia. In line with this expectation, those rare subjects (3 altogether in the two experiments) who reported volitional attempts to forget the 4 words targeted for amnesia also displayed relatively reduced recall and relatively low organization of the nontargeted words. Nevertheless, subjects who have the requisite hypnotic talent can evidently attend retrieval cues in order to recall nontargeted words, even though selective amnesia for the targeted words remains intact.
Hypnotic Ability and Selective Amnesia
Selective hypnotic amnesia is evidently restricted to high hypnotizable subjects, regardless of whether or not amnesia suggestions are preceded by a hypnotic induction. The results of Experiment 1 are consistent with K. S. Bowers's (1977) assertion that high hypnotizability is more important for converting an idea into a suggested effect than are specific hypnotic procedures. The results of Experiment 2 also suggest that subjects who are high hypnotizable and who pass the posthypnotic-amnesia item on prescreening tests of hypnotic susceptibility are very likely to exhibit selective amnesia in subsequent tests of it. Selective amnesia was a relatively rare occurrence in Experiment 1, even among high hypnotizable subjects. Those subjects were not, however, prescreened for demonstrated amnesic ability.
Hypnotic Versus Posthypnotic Conditions and Immediate Versus Delay Conditions
Experiment 2 revealed that neither hypnotic versus posthypnotic procedures, on one hand, nor immediate versus delayed presentation of the amnesia trial, on the other, differentially affected the extent of amnesia, its selectivity, or its nonvolitional quality. Thus, the fact that Experiment 1 uses posthypnotic amnesia and Spanos (1986) used hypnotic amnesia is not a difference that makes a difference.
Hypnotic Amnesia: Toward a Cognitive View
We agree with Spanos (1986) that people may sometimes intentionally attempt to forget things; indeed, such deliberate forgetting is the basis for Freud's very first model of repression (Breuer & Freud, 1974/1893–1895). We further agree that such deliberate efforts to forget may sometimes be the mechanism of achieving hypnotically suggested amnesia. However, the success of such deliberate efforts to forget is surely compromised by the presence of various mnemonic cues. To illustrate, a broken romance can be difficult to forget when one is surrounded by memorabilia of the former relationship: pictures of the person, favorite songs, ticket stubs for concerts attended together, and so forth. Such momentos seem automatically to activate memories of the person's face and form, shared experiences, and the associated pain of love lost, and they do so in spite of the efforts to forget the person. The organizational cues in the selective-amnesia paradigm are like ticket stubs—they make it difficult to forget what one has intentionally tried to put out of one's mind. Consequently, a deliberate attempt to forget all 16 words may be more successful than a deliberate attempt to forget only 4 of them, precisely because one is not confronted with so many recall cues.
Consider now another common example of forgetting, the inability to remember a friend's name, just when one is about to introduce the friend to another person. The forgotten name remains inaccessible, despite high motivation to recall it and despite the familiarity and physical presence of the person—both powerful mnemonic cues for name recall. Clearly, this kind of forgetting is not strategically enacted; it is forgetting despite a concerted effort to remember and despite the presence of powerful mnemonic cues. Our view is that hypnotic amnesia—in its most fully realized form—is a lot like being unable to recall the name of a familiar person one is about to introduce. By this understanding, suggested amnesia, especially selective amnesia, is like trying to recall something and failing, rather than deliberately attempting to forget something and succeeding.
There is increasing evidence that fully functional human memory involves both trace information and the conscious experience of remembering it and that these two facets of human memory can become disconnected or dissociated in various ways (K. S. Bowers & Hilgard, 1988; Jacoby, Kelley, & Dywan, 1989; Schacter, 1987). Of particular relevance here is the fact that the conscious experience of remembering can be absent, even though trace information of the unrecalled event is clearly activated, as demonstrated by its implicit impact on behavior (e.g., Eich, 1984; Jacoby & Witherspoon, 1982; Kihlstrom, 1980; Schacter, 1987). Indeed, a person's concerted efforts to render activated trace information fully conscious may fail (as in forgetting the name of a friend), and we propose that suggestions for hypnotic or posthypnotic amnesia, delivered to a high hypnotizable person, dramatically increase the likelihood of such a failure.
In effect, we are arguing that the “secret” of suggested amnesia resides in a distinction between activating a memory, on one hand, and activating consciousness of it, on the other. Schacter (1989) recently argued that conscious experiences of remembering, knowing, and so forth all depend on the functioning of a specific mechanism or system that is distinct from, but interacts with, modular mechanisms that process and represent various types of information. I refer to this system simply as the Conscious Awareness System (CAS). By the present view, activation at the modular level—in a particular perceptual or memory system, for example—is not sufficient to produce conscious awareness of the activated representation. Such awareness depends on the activation of CAS by the output of perceptual or memory modules. (p. 364)
So, if the output of the activated memory does not in turn activate the CAS, there is no conscious recall of that memory, though it may implicitly inform a great deal of the subject's behavior, including perhaps continuing efforts to represent the activated information in consciousness.
Suggestions for hypnotic and posthypnotic amnesia typically state quite explicitly what the subject is to forget, thereby activating the information to be forgotten. However, the suggestions also reduce the likelihood that activated information will in turn activate consciousness of it. If activating information and activating consciousness of it are separate and distinct cognitive processes, the apparent paradox of selective amnesia disappears: A person forgets material targeted for amnesia because a suggestion-activated memory is rendered temporarily unable to activate consciousness of the memory. Just how or why an activated memory can be temporarily disabled in this fashion is not entirely clear, just as it is not clear why the name of a friend one wishes to introduce becomes temporarily inaccessible, even though memory of it is at least partially activated by the friend's physical presence.
Admittedly, these two mnemonic lapses differ in that forgetting all the words in a category is explicitly suggested, whereas forgetting a friend's name is not. However, it does not seem unreasonable to assume that mechanisms involved in spontaneous forgetting can also be mobilized in the production of suggested forgetting. Pertinent here is the fact that many subjects in our two experiments experienced themselves during the amnesia trial as unable to recall some words, despite a specific suggestion that they would be unable to remember having forgotten anything. Indeed, 14 subjects in Experiment 2 were unable to recall an average of 3 of 4 bird names, even though they remembered the particular category targeted for amnesia (i.e., birds). The subjects' knowledge that they were forgetting birds ought to have been a very powerful cue for the recall of them, just as someone's presence is ordinarily a very powerful cue for recalling the person's name. Nevertheless, in both cases, there can be failures of such cues to activate consciousness of the relevant memory. We need a model of memory that can convincingly account for failures of recall that occur despite the presence of powerful mnemonic cues.
In sum, our view is that suggested amnesia activates the information to be forgotten while deactivating consciousness of it. This account implies that suggested amnesia reflects a temporary breakdown in the cognitive processes ordinarily involved in generating consciousness of a memory rather than an intentional and motivated attempt to forget the material targeted for amnesia. We are confident that in the long run, a social psychological model of hypnosis, which emphasizes motivated, strategic efforts to forget, will prove insufficient to account for much of what is interesting about suggested amnesia. Rather, an explanation based on a sophisticated model of memory will be necessary to understand just how hypnotically suggested forgetting occurs (cf. Kihlstrom, 1986).
1 Wilson and Kihlstrom (1986) suggested that categorical disorganization is not a necessary concomitant of suggested amnesia. Spanos, Bertrand, and Perlini (1988) offered a reinterpretation of Wilson and Kihlstrom's data and suggested that the proper analysis for demonstrating the disorganization effect was not completed. These criticisms were in turn challenged by the original authors (Kihlstrom & Wilson, 1988). We suspect that the last word has not been heard on this subject.
2 Spanos (1986) argued that reports of nonvolition in suggested behavior represent attributional errors; on the other hand, he argued that reports of strategies to achieve the suggested state of affairs correctly represent the actual means of producing them (cf. P. E. Bowers, 1986). Logically, the reverse may also be true and is closer in some ways to the spirit of Hilgard's (1977) neodissociation view of hypnosis. We are unlikely to determine the relative validity of retrospective reports of nonvolitional experience, on one hand, and of strategic enactments, on the other, simply by collecting more such reports. Several unpublished reports have attempted to address the issue of whether reports of nonvolition accurately reflect the absence of high-level cognitive effort in the production of hypnotically suggested responses (K. S. Bowers, 1989; K. S. Bowers & Davidson, in press; Hughes, 1988; Miller & Bowers, 1990).
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Submitted: June 14, 1990 Revised: October 9, 1990 Accepted: October 27, 1990
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Source: Journal of Abnormal Psychology. Vol. 100. (2), May, 1991 pp. 133-143)
Accession Number: 1991-23405-001
Digital Object Identifier: 10.1037/0021-843X.100.2.133
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