Memory, Amnesia, and Dissociative Identity Disorder

Inter-identity amnesia for neutral episodic self-referential and autobiographical memory in Dissociative Identity Disorder: An assessment of recall and recognition

Amnesia is a core diagnostic criterion for Dissociative Identity Disorder (DID), however previous research has indicated memory transfer. As DID has been conceptualised as being a disorder of distinct identities, in this experiment, behavioral tasks were used to assess the nature of amnesia for episodic 1) self-referential and 2) autobiographical memories across identities. Nineteen DID participants, 16 DID simulators, 21 partial information, and 20 full information comparison participants from the general population were recruited. In the first study, participants were presented with two vignettes (DID and simulator participants received one in each of two identities) and asked to imagine themselves in the situations outlined. The second study used a similar methodology but with tasks assessing autobiographical experience. Subjectively, all DID participants reported amnesia for events that occurred in the other identity. On free recall and recognition tasks they presented a memory profile of amnesia similar to simulators instructed to feign amnesia and partial information comparisons. Yet, on tests of recognition, DID participants recognized significantly more of the event that occurred in another identity than simulator and partial information comparisons. As such, results indicate that the DID performance profile was not accounted for by true or feigned amnesia, lending support to the idea that reported amnesia may be more of a perceived than actual memory impairment.

The Return of the Repressed: The Persistent and Problematic Claims of Long-Forgotten Trauma

Can purely psychological trauma lead to a complete blockage of autobiographical memories? This long-standing question about the existence of repressed memories has been at the heart of one of the most heated debates in modern psychology. These so-called memory wars originated in the 1990s, and many scholars have assumed that they are over. We demonstrate that this assumption is incorrect and that the controversial issue of repressed memories is alive and well and may even be on the rise. We review converging research and data from legal cases indicating that the topic of repressed memories remains active in clinical, legal, and academic settings. We show that the belief in repressed memories occurs on a nontrivial scale (58%) and appears to have increased among clinical psychologists since the 1990s. We also demonstrate that the scientifically controversial concept of dissociative amnesia, which we argue is a substitute term for memory repression, has gained in popularity. Finally, we review work on the adverse side effects of certain psychotherapeutic techniques, some of which may be linked to the recovery of repressed memories. The memory wars have not vanished. They have continued to endure and contribute to potentially damaging consequences in clinical, legal, and academic contexts.

Interidentity amnesia in dissociative identity disorder

INTRODUCTION

Patients diagnosed with dissociative identity disorder (DID) usually present with alternative personality states (alters) who take separate control of consciousness. Commonly, one alter will claim they have no awareness of events which took place when another alter was in control. However, some kinds of material are transferred across the alter boundary. Huntjens et al. devised an objective method of demonstrating such transfer.

METHODS

In the main study, following Huntjens et al., for three patients, two alters were taught different sets of nouns. The following week, one of the alters was given a recognition memory test including both sets plus distractor words. The patients in the Huntjens experiment responded in the same way to words in both sets.

RESULTS

In the present experiemnt, two of the patients tested had pairs of alters where there was no interference from the material which was presented to the other alter. In one of these cases, there was breakthrough with one pairing of alters, a pattern matched in a subsidiary experiment.

CONCLUSIONS

The population of individuals with DID are not homogeneous with respect to the depth of the blocking of episodic material from one alter to another.

Dissociative Tendencies, Attention, and Memory

Two groups of college students were selected on the basis of their scores on the Dissociative Experiences Scale (DES). The high-DES group (score > 20, M = 29.6; n = 54) and low-DES group (score < 10, M = 5.1; n = 54) both completed the standard and a new dualtask version of the Stroop ink-naming task with xs (baseline condition) and color, neutral, and emotionally charged words. Free recall results indicated that high-DES participants remembered fewer emotionally charged words than low-DES participants. We found a crossover interaction for Stroop interference: High-DES participants showed more interference (conflicting color – baseline latency for ink naming) in a selective-attention Stroop task and less interference in the dualtask Stroop task. The interaction between attentional context and dissociation for Stroop interference and the free recall results are consistent with a cognitive-environments view of dissociative tendencies. In this view, dissociative tendencies, which have been otherwise speculated to be largely deleterious, can be advantageous in certain contexts.

Dissociative identity disorder: An empirical overview

OBJECTIVE

Despite its long and auspicious place in the history of psychiatry, dissociative identity disorder (DID) has been associated with controversy. This paper aims to examine the empirical data related to DID and outline the contextual challenges to its scientific investigation.

METHODS

The overview is limited to DID-specific research in which one or more of the following conditions are met: (i) a sample of participants with DID was systematically investigated, (ii) psychometrically-sound measures were utilised, (iii) comparisons were made with other samples, (iv) DID was differentiated from other disorders, including other dissociative disorders, (v) extraneous variables were controlled or (vi) DID diagnosis was confirmed. Following an examination of challenges to research, data are organised around the validity and phenomenology of DID, its aetiology and epidemiology, the neurobiological and cognitive correlates of the disorder, and finally its treatment.

RESULTS

DID was found to be a complex yet valid disorder across a range of markers. It can be accurately discriminated from other disorders, especially when structured diagnostic interviews assess identity alterations and amnesia. DID is aetiologically associated with a complex combination of developmental and cultural factors, including severe childhood relational trauma. The prevalence of DID appears highest in emergency psychiatric settings and affects approximately 1% of the general population. Psychobiological studies are beginning to identify clear correlates of DID associated with diverse brain areas and cognitive functions. They are also providing an understanding of the potential metacognitive origins of amnesia. Phase-oriented empirically-guided treatments are emerging for DID.

CONCLUSIONS

The empirical literature on DID is accumulating, although some areas remain under-investigated. Existing data show DID as a complex, valid and not uncommon disorder, associated with developmental and cultural variables, that is amenable to psychotherapeutic intervention.

Shifting self, shifting memory: testing the self-memory system model with hypnotic identity delusions

According to Conway's self-memory system (SMS) model, autobiographical memories may be facilitated, inhibited, or misremembered to be consistent with current self. In 3 experiments, the authors tested this by hypnotically suggesting an identity delusion and indexing whether this shift in self produced a corresponding shift in autobiographical memory. High hypnotizable participants displayed a compelling identity delusion and elicited specific autobiographical events that they could justify when challenged. These memories were reinterpretations of previous experiences that supported the suggested identity. Importantly, autobiographical memories that were no longer consistent with the hypnotically deluded self were less accessible than other memories. The authors discuss these findings in the context of Conway's SMS model and propose 2 accounts of autobiographical remembering during hypnotic and clinical delusions.

Inter-identity autobiographical amnesia in patients with dissociative identity disorder

Background

A major symptom of Dissociative Identity Disorder (DID; formerly Multiple Personality Disorder) is dissociative amnesia, the inability to recall important personal information. Only two case studies have directly addressed autobiographical memory in DID. Both provided evidence suggestive of dissociative amnesia. The aim of the current study was to objectively assess transfer of autobiographical information between identities in a larger sample of DID patients.

Methods

Using a concealed information task, we assessed recognition of autobiographical details in an amnesic identity. Eleven DID patients, 27 normal controls, and 23 controls simulating DID participated. Controls and simulators were matched to patients on age, education level, and type of autobiographical memory tested.

Findings

Although patients subjectively reported amnesia for the autobiographical details included in the task, the results indicated transfer of information between identities.

Conclusion

The results call for a revision of the DID definition. The amnesia criterion should be modified to emphasize its subjective nature.

Defending a Diagnostic Pariah: Validatinq the Categorisation of Dissociative Identity Disorder

In past decades and still, in contemporary society, the notion and validity of the phenomenon of multiple personalities, or dissociative identities, within a single individual, have resulted in much debate and discord among mental health care professionals. Even with diverging opinions on the subject, the current Diagnostic and Statistical Manual of Mental Disorders bears proof of the genuine nature of what is now termed Dissociative Identity Disorder (DID). In this paper, the existence of DID per se is not questioned, but rather, whether this disorder can be reliably identified and validly categorised. There are four factors that will be assessed: childhood trauma, prevalence ratings, media influences, and psycho-physiological perspectives. First, traumatic experiences in childhood are commonly held to be the primary cause of this disorder; however, issues arise with regard to the intensity, duration and kind of abuse, as well as the measures in recording such abuse. Second, the prevalence ratings highlight the dramatic increase of diagnosis in the 1980s, with perspectives supporting both an under- and over-diagnosis of the disorder. Third, vast media influences may have played a role in the over-diagnosis of DID, such that the number of cases alters per person, and rates of ritual satanic abuse increased dramatically, with subsequent sharp decline. Last, psycho-physiological experimental studies may suggest the validity of this diagnostic category, but these studies may also merely demonstrate the ability for intense concentration and/or a desire for role-play. In essence, evidence either supporting or opposing the validity of current categorisation of this disorder seems to be unconvincing and inconclusive. However, depending on the perceived ontology of this disorder, further study may be directed toward parental coping strategies to reduce child abuse or mandatory warnings to practitioners on the susceptibility of certain patients.

Dissociative disorders

The dissociative disorders, including "psychogenic" or "functional" amnesia, fugue, dissociative identity disorder (DID, also known as multiple personality disorder), and depersonalization disorder, were once classified, along with conversion disorder, as forms of hysteria. The 1970s witnessed an "epidemic" of dissociative disorder, particularly DID, which may have reflected enthusiasm for the diagnosis more than its actual prevalence. Traditionally, the dissociative disorders have been attributed to trauma and other psychological stress, but the existing evidence favoring this hypothesis is plagued by poor methodology. Prospective studies of traumatized individuals reveal no convincing cases of amnesia not attributable to brain insult, injury, or disease. Treatment generally involves recovering and working through ostensibly repressed or dissociated memories of trauma; at present, there are few quantitative or controlled outcome studies. Experimental studies are few in number and have focused largely on state-dependent and implicit memory. Depersonalization disorder may be in line for the next "epidemic" of dissociation.

Memory transfer for emotionally valenced words between identities in dissociative identity disorder

The present study aimed to determine interidentity retrieval of emotionally valenced words in dissociative identity disorder (DID). Twenty-two DID patients participated together with 25 normal controls and 25 controls instructed to simulate DID. Two wordlists A and B were constructed including neutral, positive and negative material. List A was shown to one identity, while list B was shown to another identity claiming total amnesia for the words learned by the first identity. The identity claiming amnesia was tested for intrusions from list A words into the recall of words from list B and recognition of the words learned by both identities. Test results indicated no evidence of total interidentity amnesia for emotionally valenced material in DID. It is argued that dissociative amnesia in DID may more adequately be described as a disturbance in meta-memory functioning instead of an actual retrieval inability.

Researching dissociative identity disorder: practical suggestions and ethical implications

This article's purpose is to aid researchers who are interested in conducting research with dissociative populations, but who may not have extensive experience in this area. Researching dissociative identity disorder (DID) comes with many challenges. In this article, the ethics and logistics involved in selecting and implementing research methodology with DID samples are considered. This advice is centered in the author's experience of conducting research with adults in North American hospital and community settings. Researchers in this area should design data collection procedures for maximum flexibility and participant comfort, while maintaining an acceptable level of scientific rigor. Training is essential so that both principal investigators and assistants are able to deal sensitively with trauma survivors. Psychology researchers have a unique ability to be aware of hierarchy and power in the experimental setting, and to consider these issues in order to convey respect for participants.

Cognitive inhibition and interference in dissociative identity disorder: The effects of anxiety on specific executive functions

Using an experimentally based, computer-presented task, this study assessed cognitive inhibition and interference in individuals from the dissociative identity disorder (DID; n=12), generalized anxiety disorder (GAD; n=12) and non-clinical (n=12) populations. Participants were assessed in a neutral and emotionally negative (anxiety provoking) context, manipulated by experimental instructions and word stimuli. The DID sample displayed effective cognitive inhibition in the neutral but not the anxious context. The GAD sample displayed the opposite findings. However, the interaction between group and context failed to reach significance. There was no indication of an attentional bias to non-schema specific negative words in any sample. Results are discussed in terms of the potential benefit of weakened cognitive inhibition during anxious arousal in dissociative individuals.

Procedural memory in dissociative identity disorder: When can inter-identity amnesia be truly established?

In a serial reaction time task, procedural memory was examined in Dissociative Identity Disorder (DID). Thirty-one DID patients were tested for inter-identity transfer of procedural learning and their memory performance was compared with 25 normal controls and 25 controls instructed to simulate DID. Results of patients seemed to indicate a pattern of inter-identity amnesia. Simulators, however, were able to mimic a pattern of inter-identity amnesia, rendering the results of patients impossible to interpret as either a pattern of amnesia or a pattern of simulation. It is argued that studies not including DID-simulators or simulation-free memory tasks, should not be taken as evidence for (or against) amnesia in DID.

Transfer of newly acquired stimulus valence between identities in dissociative identity disorder (DID)

Patients with Dissociative Identity Disorder (DID) frequently report episodes of interidentity amnesia, that is amnesia for events experienced by other identities. The goal of the present experiment was to test the implicit transfer of trauma-related information between identities in DID. We hypothesized that whereas declarative information may transfer from one identity to another, the emotional connotation of the memory may be dissociated, especially in the case of negative, trauma-related emotional valence. An evaluative conditioning procedure was combined with an affective priming procedure, both performed by different identities. In the evaluative conditioning procedure, previously neutral stimuli come to refer to a negative or positive connotation. The affective priming procedure was used to test the transfer of this acquired valence to an identity reporting interidentity amnesia. Results indicated activation of stimulus valence in the affective priming task, that is transfer of emotional material between identities.

Dissociative style and individual differences in verbal working memory span

Dissociative style is mostly studied as a risk factor for dissociative pathology, but it may also reflect a fundamental characteristic of healthy information processing. Due to the close link between attention and working memory and the previous finding of enhanced attentional abilities with a high dissociative style, a positive relationship was also expected between dissociative style and verbal working memory span. In a sample of 119 psychology students, it was found that the verbal span of the high-dissociative group was about half a word larger than of the medium and low-dissociative groups. It is suggested that dissociative style may be one of only very few individual differences that is directly relevant to consciousness research.

Assessing markers of working memory function in dissociative identity disorder using neutral stimuli: a comparison with clinical and general population samples

OBJECTIVES

Memory functioning is a central conceptual and phenomenological aspect of dissociative identity disorder (DID). Most empirical work on memory functions in DID has focused on retrieval deficits either within or between dissociated identities. The current study attempted to remedy the scant attention given to working memory functioning.

METHOD

In samples representing the DID, non-clinical, depressed, posttraumatic stress disorder (PTSD) and psychosis populations (n = 10 per group), neutral stimuli were used to examine three markers of working memory functioning: one measuring inhibition; one assessing facilitation; and one measuring interference.

RESULTS

With the exception of the psychosis sample all groups displayed significant negative priming in the distractor inhibition condition. Facilitation effects were demonstrated by the DID and PTSD groups only. Interference effects were evident in all samples, though the DID and non-clinical groups demonstrated significantly more interference than the psychosis cohort. Distractor inhibition was related to overall schizotypy scores, and dissociation was related to scores in the facilitation condition.

CONCLUSIONS

The DID sample displayed a completely distinct functional working memory profile to the psychosis sample when assessed with emotionally neutral stimuli. However, the working memory profile in the DID sample was not entirely dissimilar to the other comparison groups.

Interidentity amnesia for neutral, episodic information in dissociative identity disorder

Interidentity amnesia is considered a hallmark of dissociative identity disorder (DID) in clinical practice. In this study, objective methods of testing episodic memory transfer between identities were used. Tests of both recall (interference paradigm) and recognition were used. A sample of 31 DID patients was included. Additionally, 50 control subjects participated, half functioning as normal controls and the other half simulating interidentity amnesia. Twenty-one patients subjectively reported complete one-way amnesia for the learning episode. However, objectively, neither recall nor recognition scores of patients were different from those of normal controls. It is suggested that clinical models of amnesia in DID may be specified to exclude episodic memory impairments for emotionally neutral material.

Posthypnotic amnesia for a first romantic relationship: Forgetting the entire relationship versus forgetting selected events

This experiment investigated the impact of suggestion focus on posthypnotic amnesia (PHA) for memories of a first romantic relationship. During hypnosis, high and low hypnotisable participants recalled specific memories from this period in response to 10 cue phrases (Elicitation). They then received a PHA suggestion that targeted either the entire period or specific memories from that period. Participants' explicit memory was indexed by cued recall after PHA was administered (memories recalled to "old" and "new" cues; Recall 1) and after it was cancelled (Recall 2). A social judgement task indexed dissociations between implicit and explicit memory. PHA had the greatest impact on highs', but not lows', memory performance (in terms of memories recalled to old cues, recall latency, and qualitative memory ratings) when the suggestion targeted the entire period rather than specific events. We discuss these findings in terms of the parameters of PHA's influence on memory, its value for exploring the nature and structure of autobiographical memory, and its utility as a laboratory analogue of functional amnesia.

Directed forgetting between, but not within, dissociative personality states

To investigate amnesia between identities in dissociative identity disorder (DID), the authors assessed explicit and implicit memory performance on a directed-forgetting task in 12 DID patients who switched from one state to an "amnesic" state between presentation and memory testing. DID patients were instructed either to remember or to forget neutral and emotional words. Besides an overall decrease in explicit memory, patients demonstrated selective forgetting of to-be-forgotten, but not of to-be-remembered words in the amnesic state. Patients did not exhibit any directed forgetting within the same state. Implicit memory was fully preserved across states. Independent of state, patients recalled more emotional than neutral information. These results may extend the conceptualization of memory processes in DID, suggesting an important role for retrieval inhibition.

Perceptual and conceptual priming in patients with dissociative identity disorder

The present study examined implicit memory transfer in patients with dissociative identity disorder (DID). To determine priming impairments in DID, we included both several perceptual priming tasks and a conceptual priming task using neutral material. We tested a large sample of DID patients (n = 31), in addition to 25 controls and 25 DID simulators, comparable on sex, age, and education. Controls replicated conceptual priming results of Vriezen, Moscovitch, and Bellos (1995) by showing that conceptual priming seems to require the formation of domain-specific semantic representations, denoting either sensory or functional object attributes. We extended a study performed by Schacter, Cooper, and Delaney (1990) by demonstrating priming for impossible object using the sensitive priming index of response times. The simulators in the study were not able to simulate interidentity amnesia on the implicit memory tasks employed. Partly in contrast to participants in previous studies, DID patients showed evidence of perceptual priming as well as conceptual priming comparable to that of controls. DID patients thus displayed normal implicit memory performance.

Alters in dissociative identity disorder. Metaphors or genuine entities?

How should the different identities (i.e., alters) that are thought to be typical for dissociative identity disorder (DID) be interpreted? Are they just metaphors for different emotional states or are they truly autonomous entities that are capable of willful action? This issue is important because it has implications for the way in which courts may handle cases that involve DID patients. Referring to studies demonstrating that alters of DID patients differ in their memory performance or physiological profile, some authors have concluded that alters are more than just metaphors. We argue that such line of reasoning is highly problematic. There is little consensus among authors about the degree to which various types of memory information (implicit, explicit, procedural) may leak from one to the other alter. Without such theoretical accord, any given outcome of memory studies on DID may be taken as support for the assumption that alters are in some sense "real." As physiological studies on alter activity often lack proper control conditions, most of them are inconclusive as to the status of alters. To date, neither memory studies nor psychobiological studies have delivered compelling evidence that alters of DID patients exist in a factual sense. As a matter of fact, results of these studies are open to multiple interpretations and in no way refute an interpretation of alters in terms of metaphors for different emotional states.

Posthypnotic amnesia for autobiographical episodes: a laboratory model of functional amnesia?

Extreme variation in the accessibility of autobiographical memory is a major characteristic of functional amnesia. On the basis of its ability to temporarily disrupt the retrieval of memory material, posthypnotic amnesia (PHA) has been proposed as a laboratory analogue of such amnesia. However, most PHA research has focused on relatively simple, nonpersonal information learned during hypnosis. This experiment extended PHA to autobiographical memory by examining high- and low-hypnotizable subjects' explicit and implicit memory of two autobiographical episodes, one of which was targeted by a PHA suggestion. The effects of PHA were consistent with the major features of functional amnesia: PHA disrupted retrieval of autobiographical information, produced a dissociation between implicit and explicit memory, and was reversible. The nature of PHA's effect on autobiographical memory and the potential utility of a PHA paradigm for investigating functional amnesia are discussed.

Toward an etiology of dissociative identity disorder: a neurodevelopmental approach

This article elaborates on Putnam's "discrete behavioral states" model of dissociative identity disorder (Putnam, 1997) by proposing the involvement of the orbitalfrontal cortex in the development of DID and suggesting a potential neurodevelopmental mechanism responsible for the development of multiple representations of self. The proposed "orbitalfrontal" model integrates and elaborates on theory and research from four domains: the neurobiology of the orbitalfrontal cortex and its protective inhibitory role in the temporal organization of behavior, the development of emotion regulation, the development of the self, and experience-dependent reorganizing neocortical processes. The hypothesis being proposed is that the experience-dependent maturation of the orbitalfrontal cortex in early abusive environments, characterized by discontinuity in dyadic socioaffective interactions between the infant and the caregiver, may be responsible for a pattern of lateral inhibition between conflicting subsets of self-representations which are normally integrated into a unified self. The basic idea is that the discontinuity in the early caretaking environment is manifested in the discontinuity in the organization of the developing child's self.

Dissociative identity disorder and memory dysfunction: the current state of experimental research and its future directions

Memory dysfunction is a central feature of dissociative identity disorder (DID). Following the memorial anomalies outlined by Putnam [Putnam, F. W. (1994). Dissociation and disturbances of self. In: D. Cicchetti & S. L. Toth (Eds.), Disorders and dysfunctions of the self, vol. 5 (pp. 251-265). Rochester, NY: University of Rochester Press; Putnam, F. W. (1995). Development of dissociative disorders. In: D. Chicchetti & D. J. Cohen (Eds.), Developmental psychopathology, vol. 2 (pp. 581-608). New York: Wiley], the experimental research using DID case studies and samples is reviewed. As a whole, research suggests that amnesic barriers between alter personalities are typically impervious to explicit stimuli, as well as conceptually driven implicit stimuli. Autobiographical memory deficits are also experimentally evident in DID. Although no experimental studies have addressed the issue of source amnesia or pseudomemories, there is some evidence that pseudomemories are an infrequent but real phenomenon in DID patients. Finally, potential deficits in working memory are outlined, including those relating to cognitive inhibition. Research directions are discussed throughout to further elucidate the nature of memory dysfunction in DID.

Autobiographical remembering and forgetting: what can hypnosis tell us?

Autobiographical memory can be characterized in terms of its reconstructive nature, its relationship with self-identity, and its shifting accessibility. Hypnosis research on personal memory has focused for the most part on its reconstructive nature. The authors examine selected contributions of hypnosis research to understand the nature and function of autobiographical memory and consider further ways in which hypnosis can make specific contributions to theoretical understanding and empirical inquiry into personal recollection. The authors provide some examples of research on various aspects of hypnosis and autobiographical memory and suggest particular ways for adding to the value and impact of such work. They argue that hypnosis researchers should continue to look for ways in which they can demonstrate and communicate the vigor and relevance of their work.

Posthypnotic amnesia for material learned before hypnosis

The impact of a suggestion for posthypnotic amnesia on material learned either before or during hypnosis was investigated across 2 experiments. In Experiment 1, very high, high, and low hypnotizable participants learned a word list either before or immediately after a hypnotic induction. During hypnosis, participants were given a suggestion for posthypnotic amnesia for the word list. After hypnosis, they were tested on recall, word-fragment, and word-recognition tasks. Experiment 2 replicated and extended Experiment 1 through application of the real-simulating paradigm. Across the 2 experiments, there was no difference in the performance of participants who learned the word list either before or during hypnosis. Although amnesia on direct memory measures was associated with high hypnotizability (Experiment 1), an explanation based on demand characteristics could not be excluded (Experiment 2). The implications of these findings for the use of post-hypnotic amnesia as a laboratory analog of disorders of autobiographical memory are discussed.