What Is Time Good for in Working Memory?

Does the extension of free time trigger spontaneous elaborative strategies in working memory?

Elaboration has emerged as a potential maintenance mechanism involved in the substantial contribution of long-term memory (LTM) to working memory (WM) performance. The objective of the current study was to determine whether elaborative strategies could be spontaneously implemented under favorable conditions. Across four experiments, the distribution of free-time periods was manipulated in a complex span task, while keeping the total amount of free time and cognitive load constant. As elaboration requires time to be set up, Experiment 1 elicited better WM performance in a condition with fewer long free-time periods compared to a condition with many short free-time periods. However, because this benefit did not persist during delayed recall, the following experiments aimed to further investigate this effect by manipulating factors supposed to modulate elaboration. In Experiment 2, half of the participants received no specific instructions regarding strategies whereas the other half were encouraged to use elaborative strategies. In Experiment 3, the to-be-maintained stimuli did or did not have LTM representations that are essential for elaboration (i.e., words or pseudowords). Finally, the last experiment used a self-strategy report to better understand the nature of the WM maintenance strategies spontaneously employed by participants. Despite a consistent effect of free time manipulation on WM recall, the explanatory assumption of elaboration was challenged by the unexpected lack of effect on LTM recall and on the type of strategy reported. Alternative explanations stemming from well-known factors influencing WM performance are discussed, and emphasis is placed on the potential contribution of direct semantic maintenance in WM.

Delayed onset facilitates subsequent retrieval of words during language comprehension

Prior research has shown that during language comprehension, memory representations associated with premodified words (e.g., the injured and dangerous bear) are retrieved faster from memory than those associated with unmodified words (e.g., the bear). Current explanations attribute this effect to the semantic richness of modified words. However, it is not clear whether the presence of modifying words are in fact necessary for a retrieval benefit. Premodifiers necessarily delay the onset of the target word (i.e., bear), and temporal delays may heighten attention to upcoming stimuli, and/or strengthen encoding by producing free time during encoding, facilitating subsequent retrieval. We therefore examined whether a simple delay in the onset of the target can produce a retrieval benefit. Our results show that delayed onset facilitates the subsequent retrieval of target words in the absence of any modifying information. These results lend support to models of language comprehension according to which delays may enhance attention to upcoming words, and also to models of working memory based on which free time replenishes encoding resources, strengthening the memory trace of encoded information and facilitating its retrieval at a subsequent point. Our results also contribute to current memory-based theories of sentence comprehension by showing that retrieval from memory may be affected by nonlinguistic factors such as delay-induced attention enhancement, or free time during encoding.

Semantic associations restore neural encoding mechanisms

Lapses in attention can negatively impact later memory of an experience. Attention and encoding resources are thought to decline as more experiences are encountered in succession, accounting for the primacy effect in which memory is better for items encountered early compared to late in a study list. However, accessing prior knowledge during study can facilitate subsequent memory, suggesting a potential avenue to counteract this decline. Here, we investigated the extent to which semantic associations-shared meaning between experiences-can counteract declines in encoding resources. Our hypothesis is that semantic associations restore neural encoding mechanisms, which in turn improves memory. We recorded scalp electroencephalography (EEG) while male and female human participants performed a delayed free recall task. Half of the items from late in each study list were semantically associated with an item presented earlier in the list. We find that semantic associations improve memory specifically for late list items and selectively modulate the neural signals engaged during the study of late list items. Relative to other recalled items, late list items that are subsequently semantically clustered-recalled consecutively with their semantic associate-elicit increased high-frequency activity and decreased low-frequency activity, a hallmark of successful encoding. Our findings demonstrate that semantic associations restore neural encoding mechanisms and improve later memory. More broadly, these findings suggest that prior knowledge modulates the orientation of attention to influence encoding mechanisms.

The emergence of all-or-none retrieval of chunks in verbal serial recall

People often subdivide a list into smaller pieces, called chunks. Some theories of serial recall assume memories are stored hierarchically, with all-or-none retrieval of chunks, but most mathematical models avoid hierarchical assumptions. Johnson (Journal of Verbal Learning and Verbal Behavior, 8(6), 725-731, 1969) found steep drops in errors following correct recalls (transitional-error probabilities) within putative chunks during multi-trial letter-list learning, and viewed this as evidence for all-or-none retrieval. Here we test whether all-or-none retrieval occurs in lists studied only once. In serial recall of six-word lists (Experiment 1), transitional-error probabilities were inconsistent with all-or-none retrieval, both when participants were instructed to subdivide and when temporal grouping induced subdivision. Curiously, the same analysis of previous temporally grouped nine-letter lists produced compelling evidence for all-or-none retrieval, which may result from recoding rather than the formation of chunks. In Experiment 2, participants were pre-trained on three-word chunks. For nine-word lists constructed from those trained chunks, transitional-error probabilities exhibited more pronounced evidence of all-or-none retrieval. Nearly all effects reversed with post-cued backward recall, suggesting mechanisms that play out over the course of recall rather than encoding of the list. In sum, subdivided lists do not result in hierarchical memories after a single study trial, although they may emerge in lists formed from chunks that are previously learned as such. This suggests a continuous transition from non-hierarchical subdivision of lists to all-or-none retrieval over the course of chunk formation.

The Relation Between Attention and Memory

The relation between attention and memory has long been deemed important for understanding cognition, and it was heavily researched even in the first experimental psychology laboratory by Wilhelm Wundt and his colleagues. Since then, the importance of the relation between attention and memory has been explored in myriad subdisciplines of psychology, and we incorporate a wide range of these diverse fields. Here, we examine some of the practical consequences of this relation and summarize work with various methodologies relating attention to memory in the fields of working memory, long-term memory, individual differences, life-span development, typical brain function, and neuropsychological conditions. We point out strengths and unanswered questions for our own embedded processes view of information processing, which is used to organize a large body of evidence. Last, we briefly consider the relation of the evidence to a range of other theoretical views before drawing conclusions about the state of the field.

Cognitive and neural mechanisms underlying false memories: misinformation, distortion or erroneous configuration?

Errors can affect our memory, yet even when there are gaps in our recollection of events, memory often serves us fairly well. Memory formation involves at least three different sub-processes, that are regulated by an underlying neural structure. From a cognitive neuropsychological perspective, a complex process of encoding, consolidating, and retrieval is involved in remembering an event, and it might be hindered by one's emotional state, physiological response to the event itself, and misinformation. As a result, it is very likely that one may struggle to remember specifics of what happened which can increase our susceptibility to the formation of false memories. This has major implications for everyday functioning, as in the case when you mistakenly remember you took your pills when you never did, or where errors have led to false accusations about trauma or abuse, and wrongful convictions of crimes. Memories sometimes contain biases and inaccuracies that prevent them from accurately recalling events. The review will provide an updated overview of current research advances on the cognitive and neural mechanisms underlying inaccurate, distorted, or false memories.

How does Working Memory Promote Traces in Episodic Memory?

A longstanding research question in cognitive psychology concerns how the underlying mechanisms of working memory impact long-term episodic memory. In this series of six experiments, we manipulated three different factors within a complex span task that interleaves memoranda and distractors to investigate the contribution of these factors to the creation of episodic traces: (1) the cognitive load of processing the distractors, (2) the number of distractors, and (3) the free time following the distractors. All three factors have been identified in the prior literature as important to maintenance in working memory and, consequently, later retrieval from episodic memory. Thus, it is important to understand their unique and joint effects to the long-term durability of memory traces. Across six experiments, delayed recall (i.e., episodic memory) of the items studied during the complex span tasks (i.e., working memory) was best accounted for by accumulated free time, whereas the effects of cognitive load and number of distractors were inconsistent or negligible. These results conflict with prior work suggesting that cognitive load and the number of distractors impact episodic memory. However, the current results replicate and extend those suggesting that time spent processing items in working memory promotes the creation of episodic memory traces.

The protective effect of educational level varies as a function of the difficulty of the memory task in ageing

This study aimed to explore the effects of age and educational level on recall performance and organisational strategies used during recall as a function of the level of memory task difficulty. Younger (n = 55, age range = 20-39 years) and older (n = 45, age range = 65-75 years) adults learned a word list where the words were either already semantically grouped (easier) or presented in pseudo-random order (harder), and then recalled the words. The number of words recalled was calculated, and an index of clustering was computed to assess organisational strategies. Older adults recalled less words than the younger ones. Older adults with a higher educational level recalled more words than their counterparts with a lower educational level when the memory task was easier, but they all performed similarly on the harder memory task. Moreover, we noted a strong positive association between educational level and semantic organisation in older adults when the memory task was easier. Regardless of educational level, older adults used semantic organisation as much as younger adults when the memory task was easier. However, when the memory task was harder, older adults showed significantly less organisational strategies than younger adults, the latter using semantic organisation to boost their recall performance. In sum, the protective effect of educational level seems to be restricted on recall performance, but not organisational strategies, in easy memory tasks providing sufficient external information about the most efficient mnemonic strategy to use.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10433-022-00724-z.

Effects of spatiotemporal (dis)continuity on working memory for human movements

Human movements are dynamic and continuous in nature. However, how the spatiotemporal continuity influences working memory for movements is still unclear. Specifically, spatiotemporal continuity of movements may facilitate integrative processing ("integration") and enhance memory performance by optimizing the encoding process, but it may also diminish memory benefits from distinctive processing ("separation"). In this study, we manipulated the continuity state (continuous/discontinuous) (Experiment 1) and its predictability (Experiment 2) of whole-body movement sequences and tested participants' working memory for observed movements with a single-probe recognition task. We formulated potential influence from spatiotemporal (dis)continuity by two opposite forces - integration vs. separation, and demonstrated a conflict between these two processes across space and time. Moreover, we found that the seemingly stimulus-driven perceptual effects from spatiotemporal (dis)continuity might be supported by a prediction-based mechanism, which guided the selection of an optimal processing strategy. Overall, our finding illustrates an interweaving relationship between spatial and temporal processing during action observation and highlights the importance of considering the dynamic and continuous nature of human movements in visual perception and working memory research.

No evidence that the retro-cue benefit requires reallocation of memory resources

Selective mechanisms allow us to prioritize items held in working memory. Does this reflect reallocation of working memory resources? We examined a critical prediction of this account-that reallocating more resources from one item to another should provide a greater benefit. We used a reward manipulation to create variable allocation of resources. Subsequently, a retro-cue instructed participants to drop a memory item. This retro-cue improved performance for the prioritized items relative to a neutral baseline. However, in contrast to the prevailing reallocation account, we found no difference between dropping a higher versus lower reward item. Importantly, removal of high versus low reward items led to better encoding of subsequently presented items, demonstrating that our reward manipulation was successful. While allocation of resources can influence the encoding and storage of new information into working memory, reallocation does not appear to be essential for selection effects in working memory.