Memory decay distinguishes subtypes of gist.

Memories are thought to become more gist-like over time. Multiple related memories might form generalized memory representations, losing specific details but enhancing or retaining gist. The time course within which gist memory emerges, however, is the subject of less consensus. To address this question, we focused our design on four kinds of gist: inferential gist (relations extracted across non-contiguous events), statistical learning (regularities extracted from a series), summary gist (a theme abstracted from a temporally contiguous series of items), and category gist (characterization of a stimulus at a higher level in the semantic hierarchy). Seventy participants completed memory encoding tasks addressing these types of gist and corresponding retrieval tasks the same evening, the morning after, and one week later, as well as an MRI at a later time point. We found little evidence that gist slowly emerges over time or that gist traces are more resistant to forgetting than detail traces. Instead, we found that initial gist memory shortly after encoding was either retained over time or decayed. Inferential gist and statistical learning were retained over a week, whereas memory for category and summary gist decayed. We discuss several interpretations for differences between these two subtypes of gist. Individual differences in REM or slow-wave sleep and hippocampal volumes did not predict changes in memory for these four kinds of gist in a healthy young adult population.

Emotional context effects on memory accuracy for neutral information.

Despite decades of study, it remains unclear how emotional contexts influence memory for non-emotional information. In two studies, we previously found memory accuracy for neutral information encoded in an emotional context differed by valence. Specifically, neutral images encoded in a negative context were remembered with similar accuracy as those encoded in a non-emotional context, and neutral images encoded in a positive context were remembered with less accuracy than a non-emotional context. This Registered Report contains a third study to replicate our original results and allow for direct comparison between the negative and positive encoding conditions. People in the positive condition showed decreased memory accuracy, but this effect was very small in size and only significant when compared to the neutral condition. Given the lack of difference between negative and neutral conditions, effects of emotion on memory are not only a function of emotional arousal. At the same time, given the nonsignificant, small difference between positive and negative conditions, effects of emotion on memory are also not solely attributable to valence. This series of studies represents a step towards re-examining the tenet that emotion enhances memory unless the experience elicits sufficiently high arousal levels such that memory is impaired.

Retained ability to extract gist in childhood-acquired amnesia: Insights from a single case.

This paper presents the performance of a young amnesic person (CJ) in the DRM task. CJ was found to be sensitive to the DRM manipulation at a level comparable to controls in recognition and at a level higher than controls in free recall. Detailed analyses of recall intrusions lent further support to the finding that CJ is able to extract gist on the basis of semantic associations. Results are discussed with reference to relevant theory as well as the potential role of an impaired and immature cognitive system in adopting a semantic gist strategy in the absence of episodic memory.

Eye-closure & the retrieval of item-specific information in recognition memory.

Two experiments investigated the effect of eye-closure on visual and auditory memory under conditions based on the retrieval of item-specific information. Experiment 1 investigated visual recognition memory for studied, perceptually similar and unrelated items. It was found that intermittent eye-closure increased memory for studied items and decreased memory for related items. This finding was reflected by enhanced item-specific and reduced gist memory. Experiment 2 used the Deese-Roediger-McDermott (DRM) paradigm to assess auditory recognition memory for studied, related and unrelated words that had (vs. had not) been accompanied by pictures during encoding. Pictures but not eye-closure produced a picture superiority effect by enhancing memory for studied items. False memory was reduced by pictures but not eye-closure. Methodological and theoretical considerations are discussed in relation to existing explanations of eye-closure and retrieval strategies.

Gist-based illusions within and across stimulus modalities in autism spectrum disorder.

Some studies have reported a low rate of false recognition (FR) in individuals with autism spectrum disorder (ASD) relative to non-autistic comparison participants (CPs). This finding, however, has not always been replicated and the source of the discrepancy remains unknown. We hypothesised that poor episodic memory functions may account for this finding. We used an adapted version of the Deese, Roediger and McDermott paradigm which presents lists of words, pictures or word-picture pairs to obtain measures of performance which reflect episodic [hits and false alarms (FAs)] and semantic (FR) memory functions. Results showed a decreased rate of FR in ASD individuals with lists of words which rose above the rate seen in non-autistic CPs with lists of word-picture pairs. This increased rate of FR in ASD was accompanied by a parallel increase in hits and a decrease in FA which reached a similar level in the two groups. Poor episodic memory functions may prevent individuals with ASD from acquiring item information which in turn precludes the formation of semantic links between items. This could render them less prone to FR.

Gist memory in the unconscious-thought effect.

The unconscious-thought effect (UTE) occurs when people are better able to make complex decisions after a period of distraction rather than immediately or after a period of conscious deliberation. This finding has often been interpreted as evidence of unconscious thinking. In two experiments, we provided the first evidence that the UTE is accompanied by enhanced memory for the gist of decision-relevant attributes and demonstrated that the cognitive demands of a distraction task moderate its effect on decision making and gist memory. It was only following a low-demand distraction task that participants chose the best alternative more often and displayed enhanced gist memory for decision-relevant attributes. These findings suggest that the UTE occurs only if cognitive resources are available and that it is accompanied by enhanced organization of information in memory, as shown by the increase in gist memory.

Episodic Memory Does Not Add Up: Verbatim-Gist Superposition Predicts Violations of the Additive Law of Probability.

Fuzzy-trace theory's assumptions about memory representation are cognitive examples of the familiar superposition property of physical quantum systems. When those assumptions are implemented in a formal quantum model (QEMc), they predict that episodic memory will violate the additive law of probability: If memory is tested for a partition of an item's possible episodic states, the individual probabilities of remembering the item as belonging to each state must sum to more than 1. We detected this phenomenon using two standard designs, item false memory and source false memory. The quantum implementation of fuzzy-trace theory also predicts that violations of the additive law will vary in strength as a function of reliance on gist memory. That prediction, too, was confirmed via a series of manipulations (e.g., semantic relatedness, testing delay) that are thought to increase gist reliance. Surprisingly, an analysis of the underlying structure of violations of the additive law revealed that as a general rule, increases in remembering correct episodic states do not produce commensurate reductions in remembering incorrect states.