Dissociation in the laboratory: a comparison of strategies

Several methods for inducing dissociation in the laboratory were examined in a sample of 78 undergraduate students. Participants scoring high or low on the Dissociative Experiences Scale participated in three dissociation challenge conditions: (a) dot-staring task, (b) administration of pulsed photic and audio stimulation and (c) stimulus deprivation. Participants recorded their dissociative experiences both before and after each of the three challenge conditions. Across conditions, high DES participants reported significantly more dissociative sensations than low DES participants, even after controlling for pre-challenge dissociation. Moreover, regardless of DES status, pulsed photo and audio stimulation produced the greatest level of dissociative symptoms. The findings suggest that the induction of dissociative symptoms in a nonclinical sample is easily accomplished in the laboratory and that those who report more dissociative symptoms in their day-to-day life exhibit more pronounced dissociative symptoms when undergoing dissociative challenge in the laboratory. Implications for the study and treatment of dissociative symptoms are discussed.     

Subjective experience guides betting decisions beyond accuracy: evidence from a metamemory illusion

The goal of this research was to test whether subjective memory experiences drive accuracy regulation decisions above and beyond objective memory indices. In four experiments (n?=?115) subjective recollection (i.e., reporting “Remember” in the Remember-Know task) was dissociated from memory accuracy by manipulating retrieval during a two-alternative forced-choice recognition task: in the Match condition the distracter was a novel exemplar of the target (e.g., a studied and an unstudied toaster) and in the Non-match condition the distracter was a novel exemplar of another studied but untested item (e.g., a studied toaster and an unstudied birdhouse). Participants were more accurate on Match trials, but reported subjective recollection more frequently on Non-match trials. Critically, participants also bet more often on Non-match trials to the detriment of their score (Experiment 1). This pattern persisted when participants were additionally required to retrieve details about items (Experiment 2) and when confidence assessments were collected (Experiment 3). Finally, participants bet more on Non-match trials even when subjective judgments were not elicited, suggesting that the decision process does not require reporting on subjective experience (Experiment 4). These results indicate that subjective memory experiences guide decision-making independent of objective accuracy and thus are critical to accuracy regulation.     

The relationship between different types of dissociation and psychosis-like experiences in a non-clinical sample

This study investigated whether detachment-type dissociation, compartmentalisation-type dissociation or absorption was most strongly associated with psychosis-like experiences in the general population. Healthy participants (N = 215) were tested with the Dissociative Experiences Scale (DES, for detachment-related dissociative experiences); the Harvard Group Scale of Hypnotic Susceptibility (HGSHS: A, for dissociative compartmentalisation); the Tellegen Absorption Scale (TAS, for non-clinical ‘functional’ dissociative experience); and two measures of psychotic-like experiences, the 21-item Peters et al. Delusions Inventory (PDI-21) and the Cardiff Anomalous Perceptions Scale (CAPS). In multiple regression analyses, DES and TAS but not HGSHS: A scores were found to be significantly associated with PDI-21 and CAPS overall scores. A post hoc hierarchical cluster analysis checking for cluster overlap between DES and CAPS items, and the TAS and CAPS items showed no overlap between items on the DES and CAPS and minimal overlap between TAS and CAPS items, suggesting the scales measure statistically distinct phenomena. These results show that detachment-type dissociation and absorption, but not compartmentalisation-type dissociation are significantly associated with psychosis-like experiences in a non-clinical population.     

Dissociative Experiences Scale Taxon and Measurement of Dissociative Pathology: Does the Taxon Add to an Understanding of Dissociation and Its Associated Pathologies?

The Dissociative Experiences Scale Taxon (DES-T) is a modified version of the Dissociative Experiences Scale (DBS) that relies on a subset of eight categorical variables to overcome errors introduced into diagnostic classification by virtue of the use of dimensional measures of dissociation (e.g., DES) that mix normal and abnormal dissociative experiences. The present study examined the diagnostic accuracy of the DES-T and the DES in two non-dissociative psychiatric samples and four dissociative disorders. Classification of the six groups by the two measures yielded more errors with the DES-T and a high degree of correlation between normal and abnormal dissociative experience. The DES-T was sensitive for only the most extreme forms of dissociative pathology. There was no support for the use of the DES-T in lieu of the DES, or for reliance on either as a definitive diagnostic measure.     

Test context affects recollection and familiarity ratings: implications for measuring recognition experiences

The binary remember/know task requires participants to dichotomize their subjective recognition experiences into those with recollection and those only with familiarity. Many variables have produced dissociative effects on remember/know judgments. In contrast, having participants make independent recollection/familiarity ratings has consistently produced parallel effects, suggesting the dissociations may be artifacts of using binary judgments. Bodner and Lindsay (2003) reported a test-list context effect with binary judgments: Increased remembering but decreased knowing for a set of critical items tested with a set of less-memorable (vs. more-memorable) items. Here we report a parallel effect of test-list context on recollection and familiarity ratings, induced by a shift in response bias. We argue that independent ratings are preferable to binary judgments because they allow participants to directly report the co-occurrence of recollection and familiarity for each item. Implications for the measurement of self-reported recognition experiences, and for accounts of recognition memory, are discussed.     

Olfactory working memory: exploring the differences in n-back memory for high and low verbalisable odorants

ABSTRACT

We describe four experiments each examining n-back performance for high and low verbalisable odorants. Participants were presented with a sequence of odorants and were required to state if the current odorant was the same or different to the odorant presented two items earlier. Experiment 1 reported superior performance for high, relative to low, verbalisable odorants and was evident despite above-chance memory performance for the low verbalisable odorants. Experiment 2 showed that such superiority persisted with a concurrent articulation condition, suggesting that the memory benefit was not a consequence of verbal recording and rehearsal. Experiment 3 employed metacognitive judgments and showed that correct 2-back responses for high verbalisable odorants received more recollection responses compared to low verbalisable odorants. Experiment 4 compared n-back performance across different stimulus types and showed that, for high verbalisable odorants, performance correlated with both letters and abstract shapes, but such correlations were absent for low verbalisable odorants. Taken together, these findings show differences in n-back performance between high and low verbalisable odorants, and show that high verbalisable odorants exhibit performance similarities with both verbal and visual stimuli. We further argue that n-back performance for low verbalisable odorants operates differently to that of high verbalisable odorants.     

The Role of Recollection and Familiarity in Nondemented Parkinson's Patients

The aim of the current study was to examine if recollection and familiarity decline in nondemented Parkinson's patients. To do so we compared a sample of older people with Parkinson's disease (n = 32) to a control sample of healthy older people (n = 32) on an associative recognition task in which we manipulated the repetition of the pairs during the study phase (half of the pairs were presented once and half twice) to obtain corrected estimates of recollection, familiarity, and false recognition based on the logic of the process-dissociation procedure. The results clearly show that recollection is impaired but familiarity is preserved in nondemented Parkinson's patients. The results show that memory for pairs in Parkinson's patients relies largely on the familiarity of each item and not on a precise recollection of associative information, supporting the idea that recollection-based monitoring processes are impaired in these patients.     

Factorial structure and psychometric properties of the French adaptation of the Dissociative Experiences Scale (DES) in non-clinical participants

IntroductionThe Dissociative Experiences Scale (DES) is a widely used instrument for assessing dissociation. However, there is disagreement regarding the internal structure of the DES and scores tend to be highly skewed.ObjectiveThe present study was designed to test the psychometric properties of a French version of the DES in non-clinical participants, in addition to applying a response scale as recommended by Wright and Loftus (1999) in order to resolve the problem of skewed scores.ResultsExploratory and confirmatory factor analysis (computed in two independent samples) suggested a two-factor solution, which seem to represent two forms of dissociation (“automatic pilot” related dissociation episodes and “defensive” dissociation episodes). Results also revealed high internal consistency, and satisfactory results in terms of skewness and floor effects. Finally, significant associations with other measures (anxiety, depression, traumatic experiences) indicate good concurrent validity.ConclusionsThis study offers evidence that the present version of the French adaptation of the DES reveals good psychometric properties. Analyses of the internal structure of the DES suggest that two types of dissociative experiences are being measured: automatic pilot-related dissociation episodes (e.g., associated with different types of cognitive failures) and defensive dissociation episodes that may act as defensive mechanisms, especially in persons who have been traumatized (e.g., the avoidance of a memory related to a traumatic event).     

Dissociative experiences are related to commissions in emotional memory

Two rival hypotheses of the link between dissociative experiences and emotional memory were tested: 1) the defence mechanism hypothesis that assumes that dissociation promotes fragmentation of emotional memory; and 2) the fantasy proneness hypothesis that claims that because of its overlap with fantasy proneness, dissociation is related to commissions in emotional memory. Undergraduates scoring high (n = 19) or low (n = 19) on the Dissociative Experiences Scale (DES) listened to an aversive story. Next, a free recall task was administered. While high dissociators made more commission errors in their free recall than did low dissociators, fantasy proneness did not account for this difference.     

Dissociation and memory suppression: A comparison of high and low dissociative individuals’ performance on the Think–No Think task

The present study examined whether high and low dissociative individuals differ in their ability to keep target stimuli out of their awareness (suppression) and how this relates to their memory of those targets during a later cued recall task. The prediction was that high dissociators display a general inability to focus attention and that their distractibility undermines successful suppression, thereby enhancing memory for suppressed items. College students with high (n = 35) and low (n = 33) scores on the Dissociative Experiences Scale participated in a Dutch version of Anderson and Green’s (2001) Think–No Think (TNT) task. Overall, a significant suppression effect emerged. However, no differences between high and low dissociators were observed. Thus, the present results do not confirm that dissociation is linked to heightened distractibility.     

Dissociative Experiences and Trauma Exposure Among Newly Arrived and Settled Young War Refugees

War-traumatized refugee adolescents are a vulnerable and understudied group. This study of two different groups of war-traumatized youth (N = 77) resettled in Sweden (newly arrived refugee adolescents, n = 42, 13–19 years, and settled students with childhood war experiences, n = 35, 11–18 years) evaluated their war experiences, refugee journey, general trauma exposure, posttraumatic stress symptoms, and dissociative experiences. Both groups had experienced many traumas and a substantial proportion reported levels consistent with posttraumatic stress (71% in the newly arrived group and 34% among the settled students) and dissociation (36% and 23%, respectively). The study also provides information about the type of adverse events experienced by war-refugee adolescents, including their own subjective appraisals of the worst events. The results show that the extent of trauma exposure and posttraumatic and dissociative symptomatology among refugee adolescents are considerable even after a period of resettlement, a finding that has educational, clinical, and social implications.     

Differential outcomes of skill training,group counseling,and individual cognitive therapy for persons with acquired visual impairment

As part of the Living Skills Training Program, group counseling and individual cognitive therapy were implemented to decrease psychological distress for adults with acquired visual impairment. This quasi‐experimental design study compared the outcomes of a 6‐month skill training program combined with a group counseling program (n = 37), with (n = 9) or without (n = 10) individual cognitive therapy, and with a control group (n = 42). The outcome measures were the Profile of Mood States and the Nottingham Adjustment Scale Japanese Version. The results showed that participants with low psychological distress decreased anxiety and increased acceptance of disability, even when they did not participate in group counseling. However, among the participants with high distress, they did not show any improvement without group counseling or individual therapy. The participants with high distress who engaged in group counseling showed an improving trend in attitudes toward others. Moreover, the participants who chose to engage in individual therapy in addition to group counseling showed decreased tension‐anxiety, depression, and fatigue, and significantly improved acceptance of disability. These results suggest that group counseling, combined with individual cognitive therapy, can be an effective part of rehabilitation treatment for clients who have high psychological distress.     

The costs of suppressing stressful memories

We investigated the costs of suppressing emotional and nonemotional memories, as evidenced in response times on a concurrent sentence verification task with three levels of syntactic complexity. Participants suppressing memories of personal negative experiences (n=26) had slower response times compared to the control group (n=23) and to participants suppressing nonemotional memories (n=25) particularly on the most complex sentences. Participants suppressing nonpersonal negative experiences (n=26) did not differ from either of the other two suppression groups. Suppression failures did not differ between conditions, but failures during the sentence task were related to the intrusiveness of the memory being suppressed. The findings indicate that different kinds of memories have different suppression costs and that even successful thought suppression can impair performance on concurrent tasks, supporting Wegner's ironic processing model in which suppression attempts must compete with other ongoing tasks for scarce mental resources.     

Sensation seeking, recognition memory, and autonomic arousal

Substantial evidence shows that sensation seeking impacts memory; however, research has not examined how sensation seeking impacts automatic familiarity and conscious-controlled recollection memory systems. The present study (N = 80) examined high and low sensation seekers’ familiarity and recollection of high and low arousal images with negative valence using behavioral and skin conductance measures. Low sensation seekers had more accurate familiarity judgments to high than low arousal images, reflecting a heightened aversive motivational system. High sensation seekers showed an opposite pattern with memory enhancement for low arousal images, regardless of old-new status. The lack of any sensation seeking effects in relation to recollection judgments suggests that this personality trait is more influential on automatic than conscious controlled memory systems.     

Individuals with pronounced schizotypal traits are particularly successful in tickling themselves

We assessed self-tickling sensations in a group of participants high in schizotypal traits (n = 27) and group of participants low in schizotypal traits (n = 27). The groups were formed by screening a pool of 397 students for extreme scores in the French version of the Schizotypal Personality Questionnaire. As observed in a previous study involving psychiatric people with auditory hallucinations and/or passivity experiences our results showed that self-applied tactile stimulations are felt to be more ticklish by healthy individuals high in schizotypal traits. In contrast, there were no significant intergroup differences in the mean tickle rating in the externally-produced tickling condition. Furthermore, more successful self-tickling was associated with more frequent self-reports of unusual perceptual experiences (such as supernatural experiences) and passivity experiences in particular (such as a feeling of being under the control of an outside force or power).     

The recollective qualities of adolescents’ and adults’ narratives about a long-ago tornado

The recollective qualities of autobiographical memory are thought to develop over the course of the first two decades of life. We used a 9-year follow-up test of recall of a devastating tornado and of non-tornado-related events from before and after the storm, to compare the recollective qualities of adolescents’ (n?=?20, ages 11 years, 11 months to 20 years, 8 months) and adults’ (n?=?14) autobiographical memories. At the time of the tornado, half of the adolescents had been younger than age 6. Nine years after the event, all participants provided evidence that they recall the event of the tornado. Adults also had high levels of recall of the non-tornado-related events. Adolescents recalled proportionally fewer non-tornado-related events; adolescents younger than 6 at the time of the events recalled the fewest non-tornado-related events. Relative to adolescents, adults produced longer narratives. With narrative length controlled, there were few differences in the recollective qualities of adolescents’ and adults’ narrative reports, especially in the case of the tornado; the recollective qualities were stronger among adolescents older at the time of the events. Overall, participants in both age groups provided evidence of the qualities of recollection that are characteristic of autobiographical memory.     

Conscious and unconscious influences on remembering information from the near and distant past: A developmental analysis

We examined adults' memory for the actors and actresses who won Academy Awards for their performances in specific motion pictures between 1992 to 1937. Fifty-six individuals between 41 to 81 years of age completed inclusion and exclusion versions of aMovie Memory Questionnaire in which they were required to identify actors and actresses who were paired with the names of movies they actually appeared in (e.g., Cher—Moonstruck) or they never appeared in (e.g., Robert DeNiro—Annie Hall), respectively. Estimates of the independent contributions of conscious and unconscious influences on recollection were obtained by analyzing subjects' performance on the inclusion and exclusion tasks via Jacoby's (1991)Process Dissociation Procedure. Results indicated that conscious recollection for motion picture information exhibited a typical retention function, whereas unconscious contributions to recollection remained relatively constant over the entire time range that was sampled. When age differences were considered, it was found that young-old participants displayed a higher level of conscious recollection than did middle-age and old-old adults. The role played by unconscious processes in recollection, however, did not vary by age group.     

Intrusion-based reasoning and depression: Cross-sectional and prospective relationships

Intrusion-based reasoning refers to the tendency to form interpretations about oneself or a situation based on the occurrence of a negative intrusive autobiographical memory. Intrusion-based reasoning characterises post-traumatic stress disorder, but has not yet been investigated in depression. We report two studies that aimed to investigate this. In Study 1 both high (n = 42) and low (n = 28) dysphoric participants demonstrated intrusion-based reasoning. High-dysphoric individuals engaged in self-referent intrusion-based reasoning to a greater extent than did low-dysphoric participants. In Study 2 there were no significant differences in intrusion-based reasoning between currently depressed (n = 27) and non-depressed (n = 51) participants, and intrusion-based reasoning did not predict depressive symptoms at 6-month follow-up. Interestingly, previously (n = 26) but not currently (n = 27) depressed participants engaged in intrusion-based reasoning to a greater extent than never-depressed participants (n = 25), indicating the possibility that intrusion-based reasoning may serve as a “scar” from previous episodes. The implications of these findings are discussed.     

The integration of emotions in memories: Cognitive‐emotional distinctiveness and posttraumatic stress disorder

The current study examined cognitive‐emotional distinctiveness (CED), the extent to which emotions are linked with event information, in memories associated with PTSD. Participants either with PTSD (n = 68) or without PTSD (n = 40) completed a modified multidimensional scaling technique to measure CED for their most negative and most positive events. The results revealed that participants in the PTSD group evidenced significantly lower levels of CED. This group difference remained significant when we limited the analysis to traumatic events that led to a PTSD diagnosis (n = 33) in comparison to control participants who nominated a traumatic event that did not result in PTSD (n = 32). Replicating previous findings, CED levels were higher in memories of negative events, in comparison to positive events. These results provide empirical evidence that memories associated with PTSD do contain special organizational features with respect to the links between emotions and memory. Implications for understanding and treating PTSD are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of aging in recollective experience: the processing speed and executive functioning hypothesis

This study was designed to investigate the effects of aging on consciousness in recognition memory, using the Remember/Know/Guess procedure (Gardiner, J. M., & Richarson-Klavehn, A. (2000). Remembering and Knowing. In E. Tulving & F. I. M. Craik (Eds.), The Oxford Handbook of Memory. Oxford University Press.). In recognition memory, older participants report fewer occasions on which recognition is accompanied by recollection of the original encoding context. Two main hypotheses were tested: the speed mediation hypothesis (Salthouse, T. A. (1996). The processing-speed theory of adult age differences in cognition. Psychological Review, 3, 403–428) and the executive-aging hypothesis (West, R. L. (1996). An application of prefrontal cortex function theory to cognitive aging. Psychological Bulletin, 120, 272–292). A group of young and a group of older adults took a recognition test in which they classified their responses according to Gardiner, J. M., & Richarson-Klavehn, A. (2000). Remembering and Knowing. In E. Tulving & F. I. M. Craik (Eds.), The Oxford Handbook of Memory. Oxford University Press. remember-know-guess paradigm. Subsequently, participants completed processing speed and executive function tests. The results showed that among the older participants, R responses decreased, but K responses did not. Moreover, a hierarchical regression analysis supported the view that the effect of age in recollection experience is determined by frontal lobe integrity and not by diminution of processing speed.