Generative memory

On second thoughts: Testing the underlying mechanisms of spontaneous future thought

The human capacity to imagine possible future events unintentionally, with minimal cognitive effort, is termed spontaneous future thought (SFT). This paper addresses an important theoretical question for cognitive science: What are the possible cognitive mechanisms underlying such SFT experiences? We contrasted three hypotheses present in the literature: the online construction hypothesis, the recasting hypothesis, and the memories of future thoughts hypothesis. Study 1 (N = 41) used novel subjective ratings which challenged the recasting mechanism: SFTs were mostly rated as dissimilar to autobiographical memories, suggesting they are not simply past experiences 'recast' as future events. Study 2 (N = 90) used a novel experimental paradigm, comparing effects of voluntary episodic future constructions and non-personal narratives upon subsequent spontaneous thought sampling. Results suggested that voluntary future constructions remain accessible to spontaneous retrieval, supporting the memories of future thoughts hypothesis. This finding, and other data presented across the two studies, still indicates a role for online construction processes in SFT, but further empirical work is needed to clarify how and when constructive processes are engaged in SFT. Taken together, these two studies represent initial efforts to elucidate the mechanisms underlying SFT, providing the first proof-of-principle that deliberately envisioned future events can reappear, without intention, in consciousness at some later time, and further supporting the dual process account of future thinking. These methods and findings provide a firm basis for subsequent experimental and longitudinal research on SFT.

A Model of Semantic Completion in Generative Episodic Memory

Many studies have suggested that episodic memory is a generative process, but most computational models adopt a storage view. In this article, we present a model of the generative aspects of episodic memory. It is based on the central hypothesis that the hippocampus stores and retrieves selected aspects of an episode as a memory trace, which is necessarily incomplete. At recall, the neocortex reasonably fills in the missing parts based on general semantic information in a process we call semantic completion. The model combines two neural network architectures known from machine learning, the vector-quantized variational autoencoder (VQ-VAE) and the pixel convolutional neural network (PixelCNN). As episodes, we use images of digits and fashion items (MNIST) augmented by different backgrounds representing context. The model is able to complete missing parts of a memory trace in a semantically plausible way up to the point where it can generate plausible images from scratch, and it generalizes well to images not trained on. Compression as well as semantic completion contribute to a strong reduction in memory requirements and robustness to noise. Finally, we also model an episodic memory experiment and can reproduce that semantically congruent contexts are always recalled better than incongruent ones, high attention levels improve memory accuracy in both cases, and contexts that are not remembered correctly are more often remembered semantically congruently than completely wrong. This model contributes to a deeper understanding of the interplay between episodic memory and semantic information in the generative process of recalling the past.

Remembering the Personal Past: Beyond the Boundaries of Imagination

What is the relation between episodic memory and episodic (or experiential) imagination? According to the causal theory of memory, memory differs from imagination because remembering entails the existence of a continuous causal connection between one’s original experience of an event and one’s subsequent memory, a connection that is maintained by a memory trace. The simulation theory rejects this conception of memory, arguing against the necessity of a memory trace for successful remembering. I show that the simulation theory faces two serious problems, which are better explained by appealing to a causal connection maintained by a memory trace. Remembering the personal past is not the same as imagining.

Jacques PL. The effects of aging and an episodic specificity induction on spontaneous task-unrelated thought

When voluntarily describing their past or future, older adults typically show a reduction in episodic specificity (e.g., including fewer details reflecting a specific event, time and/or place). However, aging has less impact on other types of tasks that place minimal demands on strategic retrieval such as spontaneous thoughts. In the current study, we investigated age-related differences in the episodic specificity of spontaneous thoughts using experimenter-based coding of thought descriptions. Additionally, we tested whether an episodic specificity induction, which increases episodic detail during deliberate retrieval of events in young and older adults, has the same effect under spontaneous retrieval. Twenty-four younger and 24 healthy older adults performed two counterbalanced sessions including a video, the episodic specificity or control induction, and a vigilance task. In the episodic specificity induction, participants recalled the details of the video while in the control they solved math exercises. The impact of this manipulation on the episodic specificity of spontaneous thoughts was assessed in the subsequent vigilance task, in which participants were randomly stopped to describe their thoughts and classify them as deliberate/spontaneous. We found no differences in episodic specificity between age groups in spontaneous thoughts, supporting the prediction that automatic retrieval attenuates the episodic specificity decrease in aging. The lack of age differences was present regardless of the induction, showing no interactions. For the induction, we also found no main effect, indicating that automatic retrieval bypasses event construction and accesses pre-stored events. Overall, our evidence suggests that spontaneous retrieval is a promising strategy to support episodic specificity in aging.

Reflecting on how we remember the personal past: missing components in the study of memory appraisal and theoretical implications

The current paper offers a selective review of the study of memory appraisal, focusing on recollections of the personal past, with the goal to bring attention to a missing component in this study. To date, memory appraisal studies have concentrated on participants' assessments of the content of their personal recollections (e.g., their perceptual detail and story-like feel), including beliefs about the accuracy of that content. Participants' assessments of reflection processes accompanying their recollections (e.g., a sense of piecing-together recollection fragments) have yet to be extensively examined. The lack of information on process-based appraisals is related to prior studies' procedural constraints (e.g., kinds of cue prompts and their timing, minimal opportunities for reflection). Reasons for addressing this missing component provide the central themes of the paper. The reasons emerge from the analysis of autobiographical cueing studies, including integration of narrative research studies and autobiographical works. The analysis leads to suggestions for future research involving the use of personal narratives that are intended to address critiques of reconstruction accounts and unresolved questions in the study of memory appraisal.

A Causal Theory of Mnemonic Confabulation

This paper attempts to answer the question of what defines mnemonic confabulation vis-à-vis genuine memory. The two extant accounts of mnemonic confabulation as “false memory” and as ill-grounded memory are shown to be problematic, for they cannot account for the possibility of veridical confabulation, ill-grounded memory, and well-grounded confabulation. This paper argues that the defining characteristic of mnemonic confabulation is that it lacks the appropriate causal history. In the confabulation case, there is no proper counterfactual dependence of the state of seeming to remember on the corresponding past representation.

Why do we remember? The communicative function of episodic memory

Episodic memory has been analyzed in a number of different ways in both philosophy and psychology, and most controversy has centered on its self-referential, 'autonoetic' character. Here, we offer a comprehensive characterization of episodic memory in representational terms, and propose a novel functional account on this basis. We argue that episodic memory should be understood as a distinctive epistemic attitude taken towards an event simulation. On this view, episodic memory has a metarepresentational format and should not be equated with beliefs about the past. Instead, empirical findings suggest that the contents of human episodic memory are often constructed in the service of the explicit justification of such beliefs. Existing accounts of episodic memory function that have focused on explaining its constructive character through its role in 'future-oriented mental time travel' neither do justice to its capacity to ground veridical beliefs about the past nor to its representational format. We provide an account of the metarepresentational structure of episodic memory in terms of its role in communicative interaction. The generative nature of recollection allows us to represent and communicate the reasons for why we hold certain beliefs about the past. In this process, autonoesis corresponds to the capacity to determine when and how to assert epistemic authority in making claims about the past. A domain where such claims are indispensable are human social engagements. Such engagements commonly require the justification of entitlements and obligations, which is often possible only by explicit reference to specific past events.

Confabulating, Misremembering, Relearning: The Simulation Theory of Memory and Unsuccessful Remembering

This article develops a taxonomy of memory errors in terms of three conditions: the accuracy of the memory representation, the reliability of the memory process, and the internality (with respect to the remembering subject) of that process. Unlike previous taxonomies, which appeal to retention of information rather than reliability or internality, this taxonomy can accommodate not only misremembering (e.g., the DRM effect), falsidical confabulation, and veridical relearning but also veridical confabulation and falsidical relearning. Moreover, because it does not assume that successful remembering presupposes retention of information, the taxonomy is compatible with recent simulation theories of remembering.

Dissociating memory traces and scenario construction in mental time travel

There has been a persistent debate about how to define episodic memory and whether it is a uniquely human capacity. On the one hand, many animal cognition studies employ content-based criteria, such as the what-where-when criterion, and argue that nonhuman animals possess episodic memory. On the other hand, many human cognition studies emphasize the subjective experience during retrieval as an essential property of episodic memory and the distinctly human foresight it purportedly enables. We propose that both perspectives may examine distinct but complementary aspects of episodic memory by drawing a conceptual distinction between episodic memory traces and mental time travel. Episodic memory traces are sequential mnemonic representations of particular, personally experienced episodes. Mental time travel draws on these traces, but requires other components to construct scenarios and embed them into larger narratives. Various nonhuman animals may store episodic memory traces, and yet it is possible that only humans are able to construct and reflect on narratives of their lives - and flexibly compare alternative scenarios of the remote future.

Setting the Records Straight: Impossible Memories and the Persistence of Their Phenomenological Qualities

This article offers a new perspective on the study of “recollections” that feel like memories despite the fact that people come to believe they are based on events that could not possibly have happened. Indeed this feeling of remembering can persist long after people change their beliefs. This new perspective emerges from the integration of the work of memory scientists with that of literary writers and historians. Shedding light on assumptions about the strength of these persistence effects, the perspective serves as an effective heuristic for guiding the study of precipitating factors that may lead people to question their recollections in the first place. This integrative perspective also invites a broader consideration of the circumstances giving rise to changes in beliefs as well as resistance to such changes. In the process, this new perspective extends and sharpens theoretical discussions about memory reconstruction processes, highlighting the role of scene making and social interactions.

Is external memory memory? Biological memory and extended mind

Clark and Chalmers (1998) claim that an external resource satisfying the following criteria counts as a memory: (1) the agent has constant access to the resource; (2) the information in the resource is directly available; (3) retrieved information is automatically endorsed; (4) information is stored as a consequence of past endorsement. Research on forgetting and metamemory shows that most of these criteria are not satisfied by biological memory, so they are inadequate. More psychologically realistic criteria generate a similar classification of standard putative external memories, but the criteria still do not capture the function of memory. An adequate account of memory function, compatible with its evolution and its roles in prospection and imagination, suggests that external memory performs a function not performed by biological memory systems. External memory is thus not memory. This has implications for: extended mind theorizing, ecological validity of memory research, the causal theory of memory.