Characteristics of memories for near-death experiences

Near-death experiences are vivid, life-changing experiences occurring to people who come close to death. Because some of their features, such as enhanced cognition despite compromised brain function, challenge our understanding of the mind-brain relationship, the question arises whether near-death experiences are imagined rather than real events. We administered the Memory Characteristics Questionnaire to 122 survivors of a close brush with death who reported near-death experiences. Participants completed Memory Characteristics Questionnaires for three different memories: that of their near-death experience, that of a real event around the same time, and that of an event they had imagined around the same time. The Memory Characteristics Questionnaire score was higher for the memory of the near-death experience than for that of the real event, which in turn was higher than that of the imagined event. These data suggest that memories of near-death experiences are recalled as “realer” than real events or imagined events.     

Traumatic memories of war veterans: not so special after all

Several authors have argued that traumatic experiences are processed and remembered in a qualitatively different way from neutral events. To investigate this issue, we interviewed 121 Croatian war veterans diagnosed with posttraumatic stress disorder (PTSD) about amnesia, intrusions (i.e., flashbacks and nightmares), and the sensory qualities of their most horrific war memories. Additionally, they completed a self-report scale measuring dissociative experiences. In contrast to what one would expect on the basis of theories emphasizing the special status of traumatic memories, amnesia, and high frequency intrusions were not particularly typical for our sample of traumatized individuals. Moreover, traumatic memories were not qualitatively different from neutral memories with respect to their stability and sensory qualities. The severity of PTSD symptoms was not significantly correlated with dissociative experiences. Our findings do not support the existence of special memory mechanisms that are unique to experiencing traumatic events.     

The many faces of amnesia

Results from studies of retrograde amnesia provide much of the evidence for theories of memory consolidation. Retrograde amnesia gradients are often interpreted as revealing the time needed for the formation of long-term memories. The rapid forgetting observed after many amnestic treatments, including protein synthesis inhibitors, and the parallel decay seen in long-term potentiation experiments are presumed to reveal the duration of short-term memory processing. However, there is clear and consistent evidence that the time courses obtained in these amnesia experiments are highly variable within and across experiments and treatments. The evidence is inconsistent with identification of basic temporal properties of memory consolidation. Alternative views include modulation of memory and emphasize the roles that hormones and neurotransmitters have in regulating memory formation. Of related interest, converging lines of evidence suggest that inhibitors of protein synthesis and of other biochemical processes act on modulators of memory formation rather than on mechanisms of memory formation. Based on these findings, memory consolidation and reconsolidation studies might better be identified as memory modulation and "remodulation" studies. Beyond a missing and perhaps unattainable time constant of memory consolidation, some current views of memory consolidation assume that memories, once formed, are generally unmodifiable. It is this perspective that appears to have led to the recent interest in memory reconsolidation. But the view adopted here is that memories are continually malleable, being updated by new experiences and, at the same time, altering the memories of later experiences. Studies of memory remodulation offer promise of understanding the neurobiological bases by which new memories are altered by prior experiences and by which old memories are altered by new experiences.     

THE CONCEPT OF PHILOSOPHICAL EXPERIENCE

Abstract: We often speak about religious experience, and sometimes we speak about metaphysical experience. Yet we seldom hear about philosophical experience. Is philosophy purely a matter of theories and theses, or does it have an experiential aspect? In this article, I argue for the following three claims. First, there is something we might call philosophical experience, and there is nothing mystical about it. Second, philosophical experiences are expressed in something quite similar to what Kant called “aesthetic judgements.” Third, philosophical experiences are expressed by using words in what Wittgenstein called “secondary sense.” Finally, I try to show the educational significance of pursing philosophical experiences. Through articulating them one might find one's ground, and through articulating them in a less private and more universal form one might raise oneself to universality. Thus, in expressing philosophical experiences one aspires to speak in a universal voice.     

The dynamics of memory: context-dependent updating

Understanding the dynamics of memory change is one of the current challenges facing cognitive neuroscience. Recent animal work on memory reconsolidation shows that memories can be altered long after acquisition. When reactivated, memories can be modified and require a restabilization (reconsolidation) process. We recently extended this finding to human episodic memory by showing that memory reactivation mediates the incorporation of new information into existing memory. Here we show that the spatial context plays a unique role for this type of memory updating: Being in the same spatial context during original and new learning is both necessary and sufficient for the incorporation of new information into existing episodic memories. Memories are automatically reactivated when subjects return to an original learning context, where updating by incorporating new contents can occur. However, when in a novel context, updating of existing memories does not occur, and a new episodic memory is created instead.     

Source accuracy data reveal the thresholded nature of human episodic memory

Episodic recollection supports conscious retrieval of past events. It is unknown why recollected memories are often vivid, but at other times we struggle to remember. Such experiences might reflect a recollection threshold: Either the threshold is exceeded and information is retrieved, or recollection fails completely. Alternatively, retrieval failure could reflect weak memory: Recollection could behave as a continuous signal, always yielding some variable degree of information. Here we reconcile these views, using a novel source memory task that measures retrieval accuracy directly. We show that recollection is thresholded, such that retrieval sometimes simply fails. Our technique clarifies a fundamental property of memory and allows responses to be accurately measured, without recourse to subjective introspection. These findings raise new questions about how successful retrieval is determined and why it declines with age and disease.     

Imagination equally influences false memories of high and low plausibility events

To examine the effects of event plausibility on people's false beliefs and memories for imagined childhood events, subjects took part in a three‐stage procedure. First, subjects rated how confident they were that they had experienced certain childhood events. They also rated their memories of the events. Second, 1 week later, subjects imagined one high, one moderate and one low plausibility event. Third, 1 week later (and 2 weeks after their initial ratings), subjects rated their confidence and memory a second time. Imagining the events made subjects more confident that they were genuine experiences and gave subjects clearer and more complete memories. Plausibility did not affect subjects' confidence but it did affect their memories. Subjects developed clearer and more complete memories for high, followed by moderate, followed by low plausibility events regardless of whether those events were imagined. We use a nested model of plausibility, belief and memory to discuss our findings. Copyright © 2008 John Wiley & Sons, Ltd.     

Psychopathic personality traits are linked to reduced false memories for negative events

Individuals scoring high on psychopathic personality traits process emotional material to a different extent than individuals with few psychopathic traits. Evidence exists that these individuals have impaired emotional memory. The question arises whether this emotional memory impairment has ramifications for the production of emotional false memories. In the present study, we investigated the production of false and true memories for emotional events in a community sample (N = 120) of individuals varying in psychopathic traits (evaluated with the Psychopathic Personality Inventory–Revised [PPI-R] questionnaire). The fearless dominance (FD) component of psychopathy interacted with the emotional impact of to-be-remembered events in the production of false memories, showing fewer negative false memories with increasing levels of FD. At the subjective level, negative false memories were not perceived as vivid memory experiences in high FD individuals. Concerning true memories, higher scores in cold-heartedness were related to fewer true memories for neutral and negative (but not positive) events. These results show that individuals with high psychopathy traits – in particular, FD – do not have a general emotional memory impairment but they process negative material in a different way than individuals with low psychopathic traits and thus are less susceptible to producing false memories for negative events.     

Mood and memories of parental rearing styles: A comparison of mood effects on questionnaire-cued and free recall of autobiographical memories

The relationship between memories of childhood experiences (e.g., adverse parenting) and adult depression often found raises questions of interpretation. On the one hand, both laboratory studies and clinicians' experiences suggest that subjects in a depressed mood frequently show a negative bias in perceptions and memories. Negative childhood memories in depressed persons might, therefore, be interpreted as epiphenomena of depressed mood instead of etiological factors. On the other hand, memories of childhood experiences seem remarkably stable across changes in depressed mood, especially when memories are elicited by means of standardized questionnaires. In the mood and memory literature several explanations for this stability are offered. For one thing, highly structured cues to elicit memories (such as in questionnaires) are hypothesized to be less susceptible to mood bias than unstructured memory cues (such as in free recall procedures). On the other hand, resource allocation theorists suggest that childhood memories, being well established and rehearsed, are relatively impervious to mood bias no matter how they are elicited. In this study we examined whether different methods of eliciting childhood memories (i.e., free recall and questionnaire-cued) are differentially susceptible to mood bias. To this aim, we used a mood induction procedure to induce depressed, neutral, and elated mood and assessed childhood memories both before and after the mood induction using both questionnaires and free recall to elicit memories. Results suggested that memories elicited by means of free recall as well as by means of questionnaire-cued recall were susceptible to depressed and elated mood bias. The implications for research addressing the link between childhood experiences and depression are discussed.     

Imagination and Memory

A growing body of literature shows that imagining contrary-to-truth experiences can change memory. Recent experiments are reviewed to show that when people think about or imagine a false event, entire false memories can be implanted. Imagination inflation can occur even when there is no overt social pressure, and when hypothetical events are imagined only briefly. Overall, studies of imagination inflation show that imagining a counter-factual event can make subjects more confident that it actually occurred. We discuss possible mechanisms for imagination inflation and find that, with evidence supporting the involvement of both source confusion and familiarity in creating inflation, the primary mechanism is still to be determined. We briefly review evidence on individual differences in susceptibility to inflation. Finally, the widespread use of imagination-based techniques in self-help and clinical contexts suggests that there may be practical implications when imagination is used as a therapeutic tool.     

Memories from the cradle

How far back can we, as adults, remember details of our life experiences? Current popular and scientific beliefs are contradictory, with the latter stipulating that personal memories do not begin until the late preschool years (age 4–5 years) and the former claiming that we not only remember being born, but can also remember in utero experiences. In this review, these beliefs are examined in a scientific context and evaluated in terms of empirical data about the development of early memory. The theory proposed here is that memories for personal experiences are not possible until the advent of the cognitive self, around the age of 18 to 24 months. This age is much earlier than that proposed as the age of the earliest memories in other scientific accounts and much later than that proposed in popular beliefs about early memory. New data from a cross-sectional and longitudinal study of early memory development and the emergence of the self clearly show the origins of personal memory coincide with the emergence of the early self.     

Metacognitive appraisal of memory inconsistency for traumatic events in Dutch veterans

Although memories of traumatic events are often remembered vividly, these memories are subject to change over time. In our previous study, we found that Dutch infantry veterans who had served in Iraq often reported stressful events at a second assessment point that they had not reported during a prior assessment point and vice versa. In the present exploratory study, we recontacted subjects from this previous study and asked how they explained the discrepancy in their memory reports between post-deployment assessment points 1 and 2. Common explanations were: interpreting the item differently, having forgotten the incident initially, repression and having accidentally incorporated someone else's experience into their own memory. Although such reports are not necessarily revelatory of the mechanisms driving discrepancies in memory reports over time, our study illuminates the metacognitive variables involved.     

Memory characteristics of recently imagined events and real events experienced previously

In two experiments, we evaluated the memory characteristics of real and imagined events as they changed over time. Memories of real events were richer than memories of imagined events, and memories of recent events were richer than of events from a week earlier. These differences interacted such that memories of real events performed in week 1 were very similar to memories of events that were imagined in week 2. Source monitoring was tested and implications for the repressed or recovered memory debate are considered.     

Are memories for sexually traumatic events "special"? A within-subjects investigation of trauma and memory in a clinical sample

According to a long-standing clinical tradition, sexually traumatic experiences are processed and recalled differently from other experiences, often leading to memory impairment. In this study, we compared the characteristics of traumatic memories for sexual violence and two other types of emotional experiences. N=44 women recruited from a local sexual trauma agency were asked to recall and describe three autobiographical events: sexual abuse/assault, a non-sexual trauma, and a positive emotional event. The characteristics of the three memory types were compared on both subjective and objective measures. Further, the potential influences of level of traumatic impact and dissociation were assessed. Results indicated that memories for sexual trauma were not impaired or fragmented relative to other memories. Instead, memories for sexual trauma were associated with a remarkably high level of vividness, detail, and sensory components. Further, high levels of traumatic impact were not associated with memory impairment. Implications for the ongoing traumatic memory debate are discussed.     

Cultural and communicative memories: contrasting Argentina’s 1976 coup d’état and the 2001 economic-political-social crisis

Studies on collective memory have recently addressed the distinction between cultural and communicative memory as a way to understand how the source of a memory affects its structure or form. When a groups’ memory is mediated by memorials, documentaries or any other cultural artifacts, collective memory is shaped by cultural memory. When it is based mostly in communication with other people, its source is communicative memory. We address this distinction by studying two recent events in Argentinean history: the 2001 economic-political-social crisis (communicative memory) and the 1976 coup (cultural memory). We also examine the political ideology and the type of memory involved in collective memory. The memory of the studied events may occur during the lifetime of the rememberer (Lived Memory) or refer to distant events (Distant Memory). 100 participants responded to a Free Recall task about the events of 2001 in Argentina. Narrative analysis allowed comparing these recalls with our 1976 study. Results show: 1) Cultural memories are more contextualised, more impersonal and less affective. 2) Communicative memories are more personal and affective. Study shows how collective memory form changes when it has a different prevalent source.     

Reducing the Negative Effect of the Retention Interval on the Composite Face Recognition

Our memories are quite fragile. We sometimes recognize something unseen as something seen before. This error often causes serious problems, such as the misidentification of composite faces in a criminal investigation. In such a scene, people occasionally claim to have seen a face that is actually a composite face consisting of facial parts separately seen before; this error is called the memory conjunction error. Although the likelihood of the memory conjunction error increases over time, previous studies suggest that it could be suppressed by the number of response options, which are expected to affect the criterion for the “Old” response. Our results show that the presence of three response options reduced the memory conjunction error. Additionally, providing information about the existence of composite faces affected the sensitivity for detecting old faces, whereas three response options affected the criterion. This study might contribute to the improvement of procedures for eyewitness testimony.     

When Photographs Create False Memories

ABSTRACT— Photographs help people illustrate the stories of their lives and the significant stories of their society. However, photographs can do more than illustrate events; in this article, we show that photographs can distort memory for them. We describe the course of our "false-memory implantation" research, and review recent work showing that photographs can sometimes increase—while other times decrease—false memories. First, we discuss research showing that a doctored photo, showing subjects taking a completely fictitious hot-air-balloon ride, can cultivate false memories for that experience. We hypothesize that the photograph helps subjects to imagine details about the event that they later confuse with reality. Second, we show that although photographs are indeed powerful sources of influence on memory, they are not necessarily as powerful as narrative. In fact, in certain circumstances, photographs might constrain imagination. Third, we discuss research showing that true photographs can also cultivate false memories. Finally, we present recent work showing that photographs can create false memories for current events.     

Exploring the basis and boundary conditions of SenseCam-facilitated recollection

SenseCam review has been shown to promote and sustain subsequent access to memories that might otherwise remain inaccessible. While SenseCam review facilitates recollection for personally experienced events, we know little about the boundary conditions under which this operates and about how underlying processing mechanisms can be optimally recruited to offset memory impairments of the sort that occur in dementia. This paper considers some of these issues with a view to targeting future research that not only clarifies our evolving body of theory about how memory works, but also informs about how memory-assistive technologies for patients might be employed to maximal effect. We begin by outlining key factors that are known to influence recollection. We then examine variability in the decline of memory function both in normal ageing and in dementia. Attention is drawn to similarities in the recollection deficits associated with depression and dementia, and we suggest that this may reflect shared underlying mechanisms. We conclude by discussing how one particular theoretical rationale can be intersected with key SenseCam capabilities to define priorities for ongoing and future SenseCam research.     

Organisation and retrieval: the generation of event clusters

The present research examined the nature of autobiographical memory event clusters. Specifically we were interested in the interplay between the content and organisation of autobiographical memory with retrieval in determining the similarity of event memories across time. Using an event cueing procedure, clusters of related event memories were generated. Participants sorted these events into meaningful groups after a delay of several weeks. The results suggest that participants' ability to perform this sorting task is dependent on their ability to reinstate the retrieval context. Further our results suggest that event clusters are chains of related event memories as opposed to clusters of interrelated event memories.