Stephen Laureys compares NDE memories

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7247850/

Abstract:

Memories of near-death experiences (NDEs) are recalled as “realer” than memories of other real or imagined events. Given their rich phenomenology, emotionality and consequentiality, it was hypothesized that they could meet some aspects of the definition of flashbulb memories. We aimed to identify and compare the episodic and non-episodic information provided in verbal recollections of NDE, flashbulb, and control autobiographical memories. The phenomenological characteristics and centrality of the memories were also compared. Twenty-five participants who had lived a NDE in a life-threatening situation were interviewed and completed the Memory Characteristics Questionnaires as well as the Centrality of Event Scale for their NDE, a flashbulb and another autobiographical memory used as control. Overall, transcribed NDE verbal recollections included a higher overall amount of details and more internal/episodic information than control autobiographical and flashbulb memories. Moreover, flashbulb memories were associated to a lower intensity of feelings while remembering and a lower personal importance, and are less reactivated and less susceptible to be remembered from a first person perspective compared to NDE and control autobiographical memories. Finally, NDE memories are the most central memories to experiencers’ identity, followed by control autobiographical and then by flashbulb memories. These findings corroborate previous studies highlighting the impact and uniqueness of NDE memories.

Introduction to the terms:

...In an effort to explain the special nature of NDE memories, different theories have been put forth. It was suggested that the significant emotionality associated with these mental events could enhance the quantity of sensory details stored in memory (Schaefer and Philippot, 2005). Besides, emotional events are more likely to be frequently rehearsed, therefore potentially increasing the amount of memorized characteristics (Thonnard et al., 2013)...

...Given their emotionality and consequentiality (i.e., the consequences of the event or aftermath; e.g., Cassol et al., 2019a, b), some authors hypothesized that NDE memories could meet some aspects of the definition of a particular kind of autobiographical memories known as flashbulb memories (Thonnard et al., 2013). Flashbulb memories refer to very vivid and long-lasting memories of the circumstances in which one learned about a shocking public event (Brown and Kulik, 1977)...

...Generally speaking narratives of autobiographical memories are known to be multifaceted in content and to include both episodic (i.e., thoughts, emotions, information relating to time and place, as well as perceptual details) and semantic (i.e., general knowledge and facts about the world and personal life) information...

Significant differences and discussions:

Differences in episodic and non-episodic subcomponents of NDE, flashbulb and autobiographical memories can be found in Table 2. Results indicated a main effect of the memory type on the amount of event and perceptual internal details (see Table 2). Specifically, post hoc comparisons indicated that NDE memories contained significantly more internal event details than autobiographical (V = 12, p < 0.001) and flashbulb memories (V = 19, p < 0.001). Autobiographical and flashbulb memories did not differ (V = 80, p = 0.223). NDE memories also showed higher ratings for internal perceptual details as compared to autobiographical (V = 3.5, p < 0.001) and flashbulb memories (V = 246, p < 0.001). Once again, autobiographical and flashbulb memories did not differ (V = 54.5, p = 0.775). No other significant difference was observed...

...Regarding visual perspective, flashbulb memories showed lower scores than NDE (V = 162.5, p < 0.001) and autobiographical memories (V = 4.5, p < 0.001) indicating that they were less susceptible to be remembered from a first-person perspective...

First, analysis of verbal recollections highlighted that NDE memories include a higher overall amount of details and a higher amount of internal/episodic details than flashbulb and autobiographical memories. This is consistent with previous studies suggesting a particularly high amount of qualitative characteristics associated with NDE memories in comparison with other types of memories (e.g., Thonnard et al., 2013; Moore and Greyson, 2017)...

...the number of internal and external details for NDE memories is significantly larger than the one observed for flashbulb and autobiographical memories...

...a NDE itself is characterized by an exceptional and unique association between unusual perceptions (such as the impression of leaving the physical body, entering a different dimension or being in an unknown spatio-temporal dimension) and a clear sensorium and intense sensation of “reality” (i.e., comparable to the sense of certainty that accompanies everyday perception; Schwaninger et al., 2002; Dell’Olio, 2010), conditions that are likely to lead to vivid memories. Second, previous studies have highlighted a tendency toward a decline in memory reports (normal forgetting process) in flashbulb memories in comparison with other emotionally arousing events (e.g., Christianson, 1989; Christianson and Engelberg, 1999). Consistency and amplification of memories over time would be conditioned by one’s degree of involvement and the severity of the emotionally arousing event (Neisser et al., 1996; van Giezen et al., 2005). In line with this view, studies including participants who were directly exposed to or personally involved in traumatic events identified different memory patterns than studies addressing flashbulb memories, in which subjects were not personally involved in the emotional event. In fact, some studies have even shown that unlike the emotionally charged traumatic events whose narratives become richer over time, flashbulb memories rather tend to decline (Krinsley et al., 2003; van Giezen et al., 2005). When looking closer at the subtypes of details that have been recalled, we identified more event and perceptual internal details within the NDE memory, as compared to flashbulb and autobiographical memories. Specifically, event details describe the unfolding of the story, and perceptual details comprise auditory, olfactory, tactile, taste, visual and spatial-temporal (allocentric-egocentric space, body position and duration) information. Some authors suggested that the overall quantity of details comprised in NDE memories could be due to the fact that self-referential information can improve recalling performances...

...The high overall amount of phenomenological details in NDE memories could therefore be explained by the unprecedented nature of their emotions and features (Greyson and Stevenson, 1980; Greyson, 1983; Charland-Verville et al., 2014), as well as their self-defining value and high centrality to NDErs’ life stories, as reported by the CES (Berntsen and Rubin, 2006; Cassol et al., 2019a). From a broader cognitive perspective, the high amount of details observed in verbal recollections of NDE memories is interesting as it suggests that people might be able to recall memories of a moment characterized by an altered state of consciousness where the brain and its associated processes are thought to be working with altered capacities. Nevertheless, it is still unclear when exactly these events are experienced as well as when their memory encoding precisely occurs...

...Indeed, NDErs have lived their NDE several decades ago in average and reported difficulties when having to recall another event from the same period. From then on, recalled autobiographical memories were events closely linked to their NDE/coma (i.e., return to their daily lives after a long hospitalization, recovery after their coma) or significant/life-changing events such as a child birth or their encounter with their spouse (i.e., categories of memories that have typically been reported as self-defining in previous studies; e.g., Cassol et al., 2019a)...

...Regarding centrality, answers to the CES revealed that NDE memories had the higher scores, followed by autobiographical memories and then by flashbulb memories. These findings corroborate previous findings and confirm the particular status of NDEs with regard to NDErs’ identities and life stories (Cassol et al., 2019a)...

Limitations:

NDErs voluntarily contacted us after calls in the lay media and our sample consequently may suffer from a self-selection bias. Moreover, given the relative scarcity of NDEs and the fact that we had to meet participants personally in accordance to the AI protocol, we were limited in the recruitment of our participants and our sample is relatively small. Therefore, results should be confirmed by larger studies. Besides, human memory is by definition a reconstructive process (Schacter et al., 1998) sensitive to numerous factors such as aging (e.g., Devitt et al., 2017); therefore, the generalizability of our results could also be impacted by the fact that all memories are drawn from a homogenous pool of NDErs. To address this issue, it would be interesting to assess autobiographical and flashbulb memories in healthy controls and to further explore the cognitive processes specific to NDErs, especially since previous studies suggest a specific cognitive profile, including a propensity for dissociation (Greyson, 2000a) and illusory recollections (Martial et al., 2017c). In the present study, we did not control for the production of false memories and the subjective feeling of remembering that may accompany false remembering (i.e., illusory recollection). In this context, it is difficult to control for the veracity of the personal memories recalled by NDErs. Nonetheless, we believe that the production of false memories and illusory recollections would have affected the three subtypes of memories equally. Indeed, some factors such as age and affect were shown to impact the emergence of false memories.

Conclusion:

Overall, NDE verbal recollections include a higher overall amount of details and a higher amount of internal/episodic details than flashbulb and autobiographical memories. More precisely, they comprise more event and perceptual internal details. Moreover, we found that flashbulb memories are associated to a lower intensity of feelings while remembering and a lower personal importance, and are less reactivated and less susceptible to be remembered from a first person perspective. Finally, NDE memories are more central than autobiographical memories, which in turn are more central than flashbulb memories. Besides, more central events contain more episodic verbal details. Overall, our results fall in line with existing literature that highlights the uniqueness of NDE memories.

I've heard that Laureys advocates for NDEs to be taken more seriously as anomalous, or at least important, phenomena, and it seems this study seems to exemplify this somewhat.

It's been known for some time that NDE memories are more intense and vivid and life-changing than normal memories of life events. Implying that they are of "realer-than-real" experiences not hallucinations of any sort.

The author, being a prudent science practitioner, tries to be very cautious and make no such conclusions, but such conclusions are obvious. I don't think such extreme caution is necessary to accept this type of evidence as part and parcel with all the other types of empirical NDE evidence that NDEs are real experiences of a transcendental spiritual nature.