A working memory dependent dual process model of the testing effect.

This Perspective article expands on a working memory-dependent dual-process model, originally proposed by Zheng et al.1, to elucidate individual differences in the testing effect. This model posits that the testing effect comprises two processes: retrieval-attempt and post-retrieval re-encoding. We substantiate this model with empirical evidence and propose future research. This model invites further studies on the trade-off between testing benefits and WM demands, facilitating the development of personalized educational practices.

Memory out of context: Spacing effects and decontextualization in a computational model of the medial temporal lobe.

Some neural representations gradually change across multiple timescales. Here we argue that modeling this "drift" could help explain the spacing effect (the long-term benefit of distributed learning), whereby differences between stored and current temporal context activity patterns produce greater error-driven learning. We trained a neurobiologically realistic model of the entorhinal cortex and hippocampus to learn paired associates alongside temporal context vectors that drifted between learning episodes and/or before final retention intervals. In line with spacing effects, greater drift led to better model recall after longer retention intervals. Dissecting model mechanisms revealed that greater drift increased error-driven learning, strengthened weights in slower drifting temporal context neurons (temporal abstraction), and improved direct cue-target associations (decontextualization). Intriguingly, these results suggest that decontextualization-generally ascribed only to the neocortex-can occur within the hippocampus itself. Altogether, our findings provide a mechanistic formalization for established learning concepts such as spacing effects and errors during learning. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

A complementary learning systems model of how sleep moderates retrieval practice effects.

While many theories assume that sleep is critical in stabilizing and strengthening memories, our recent behavioral study (Liu & Ranganath, 2021, Psychonomic Bulletin & Review, 28[6], 2035-2044) suggests that sleep does not simply stabilize memories. Instead, it plays a more complex role, integrating information across two temporally distinct learning episodes. In the current study, we simulated the results of Liu and Ranganath (2021) using our biologically plausible computational model, TEACH, developed based on the complementary learning systems (CLS) framework. Our model suggests that when memories are activated during sleep, the reduced influence of temporal context establishes connections across temporally separated events through mutual training between the hippocampus and neocortex. In addition to providing a compelling mechanistic explanation for the selective effect of sleep, this model offers new examples of the diverse ways in which the cortex and hippocampus can interact during learning.

Retrieval practice is costly and is beneficial only when working memory capacity is abundant.

Numerous studies have shown that learned information practiced by testing is better retained than that practiced by restudying (the testing effect). However, results are inconsistent regarding the effect of working memory (WM) capacity on the testing effect. Here, we hypothesize that the effect of WM only emerges when task demands challenge WM capacity. We manipulated WM demands by pretraining 30 undergraduate participants in a multi-session visual search task before an associative learning task involving a test/restudy manipulation. The results revealed that, while participants with higher WM capacity showed a consistent testing effect, the benefit of testing only emerged in participants with lower WM capacity when learning familiar stimuli (low WM demands). We simulated the results using a modified source of activation confusion (SAC) model, which implemented a dual-process account of the testing effect. The results suggested that the testing effect only emerges when WM capacity is adequate for both processes.

Correcting the hebbian mistake: Toward a fully error-driven hippocampus.

The hippocampus plays a critical role in the rapid learning of new episodic memories. Many computational models propose that the hippocampus is an autoassociator that relies on Hebbian learning (i.e., "cells that fire together, wire together"). However, Hebbian learning is computationally suboptimal as it does not learn in a way that is driven toward, and limited by, the objective of achieving effective retrieval. Thus, Hebbian learning results in more interference and a lower overall capacity. Our previous computational models have utilized a powerful, biologically plausible form of error-driven learning in hippocampal CA1 and entorhinal cortex (EC) (functioning as a sparse autoencoder) by contrasting local activity states at different phases in the theta cycle. Based on specific neural data and a recent abstract computational model, we propose a new model called Theremin (Total Hippocampal ERror MINimization) that extends error-driven learning to area CA3-the mnemonic heart of the hippocampal system. In the model, CA3 responds to the EC monosynaptic input prior to the EC disynaptic input through dentate gyrus (DG), giving rise to a temporal difference between these two activation states, which drives error-driven learning in the EC→CA3 and CA3↔CA3 projections. In effect, DG serves as a teacher to CA3, correcting its patterns into more pattern-separated ones, thereby reducing interference. Results showed that Theremin, compared with our original Hebbian-based model, has significantly increased capacity and learning speed. The model makes several novel predictions that can be tested in future studies.

Resurrected memories: Sleep-dependent memory consolidation saves memories from competition induced by retrieval practice.

Retrieval practice improves retention of tested information, and it can either impair or facilitate retention of untested information. Here, we investigated how semantic relatedness, episodic context, and sleep-dependent memory consolidation determine the effects of retrieval practice on retention of untested items. Participants studied lists of scene-word associations. Each scene was associated with two different words ("pairmates") that were either semantically related or unrelated and either in the same (temporally close) or different lists (temporally far). In three experiments, retrieval practice of scene-word associations facilitated retention of unpracticed, temporally close pairmates and impaired retention of temporally far, semantically unrelated pairmates. Critically, retrieval practice impaired retention of temporally far, semantically related pairmates if participants were unable to sleep during the retention interval, but it facilitated retention of these items if participants were able to sleep. Our findings suggest that sleep extends the benefits of testing to related information learned in temporally separate episodes.

Disrupted Modulation of Alpha and Low Beta Oscillations Mediates Temporal Sequence Memory Deficits in People With Schizophrenia.

BACKGROUND: People with schizophrenia (SZ) exhibit impaired episodic memory when relating objects to each other in time and space. Empirical studies and computational models suggest that low-frequency neural oscillations may be a mechanism by which the brain keeps track of temporal relationships during encoding and retrieval, with modulation of oscillatory power as sequences are learned. It is unclear whether sequence memory deficits in SZ are associated with altered neural oscillations. METHODS: Using electroencephalography, this study examined neural oscillations in 51 healthy control subjects and 37 people with SZ during a temporal sequence learning task. Multiple 5-object picture sequences were presented across 4 study-test blocks in either fixed or random order. Participants answered semantic questions for each object (e.g., living/nonliving), and sequence memory was operationalized as faster responses for fixed versus random sequences. Differences in oscillatory power between fixed versus random sequences provided a neural index of temporal sequence memory. RESULTS: Although both groups showed reaction time differences in late blocks (blocks 3 and 4), this evidence of sequence memory was reduced in people with SZ relative to healthy control subjects. Decreases in globally distributed prestimulus alpha (8-12 Hz) and beta 1 (13-20 Hz) power for fixed versus random sequences in late blocks were also attenuated in people with SZ relative to healthy control subjects. Moreover, changes in oscillatory power predicted individual reaction time differences and fully mediated the relationship between group and sequence memory. CONCLUSIONS: Disrupted modulation of alpha and beta 1 electroencephalography oscillations is a candidate mechanism of temporal sequence memory deficits in people with SZ.

Retrieval practice facilitation of family psychoeducation in people with early psychosis.

BACKGROUND: Providing early psychosis (EP) individuals with family psychoeducation (FPE) can reduce symptoms and improve clinical outcomes. However, relational memory problems may limit prospective utilization of FPE information. This study examines whether memory for FPE can be improved by testing participants during the initial FPE workshop presentation. METHOD: Data were obtained from 20 people with EP and 20 demographically matched healthy comparison subjects (HC). During session one, FPE was presented in small group workshops, with half of the information re-studied twice (re-study condition) and the remaining information tested twice using cued recall tasks (retrieval practice condition). One week later (session two), delayed cued recall was tested for all FPE information. "Testing effects" (i.e., better memory following retrieval practice versus re-study) were examined across all items (standard analysis) and also limited to items successfully retrieved during session one (conditionalized analysis). RESULTS: HC had better initial recall and learned more over the two retrieval practice trials than EP. However, HC also lost more information than EP over the one-week delay. Both groups produced a significant testing effect. This effect was smaller in EP versus HC across all test items, but did not differ for the conditionalized analysis. Negative symptoms were inversely correlated with delayed cued recall in EP. CONCLUSIONS: EP participants benefit from retrieval practice, with participants with less severe negative symptoms showing the greatest benefit. These results encourage use of memory tests during group psychoeducation to improve subsequent long-term recall of clinically relevant information.

Task-specific Disruptions in Theta Oscillations during Working Memory for Temporal Order in People with Schizophrenia.

Prior studies demonstrated that neural oscillations are enhanced during working memory (WM) maintenance and that this activity can predict behavioral performance in healthy individuals. However, it is unclear whether the relationship holds for people with WM deficits. People with schizophrenia have marked WM deficits, and such deficits are most prominent when patients are required to process relationships between items, such as temporal order. Here, we used EEG to compare the relationship between oscillatory activity and WM performance in patients and controls. EEG was recorded as participants performed tasks requiring maintenance of complex objects ("Item") or the temporal order of objects ("Order"). In addition to testing for group differences, we examined individual differences in EEG power and WM performance across groups. Behavioral results demonstrated that patients showed impaired performance on both Item and Order trials. EEG analyses revealed that patients showed an overall reduction in alpha power, but the relationship between alpha activity and performance was preserved. In contrast, patients showed a reduction in theta power specific to Order trials, and theta power could predict performance on Order trials in controls, but not in patients. These findings demonstrate that WM impairments in patients may reflect two different processes: a general deficit in alpha oscillations and a specific deficit in theta oscillations when temporal order information must be maintained. At a broader level, the results highlight the value of characterizing brain-behavior relationships, by demonstrating that the relationship between neural oscillations and WM performance can be fundamentally disrupted in those with WM deficits.

Familiarity acts as a reduction in objective complexity.

High-complexity stimuli are thought to place extra demands on working memory when processing and manipulating such stimuli; however, operational definitions of complexity are not well established, nor are the measures that would demonstrate such effects. Here, we argue that complexity is a relative quantity that is affected by preexisting experience. Experiment 1 compared cued-recall performance for Chinese and English speakers when the stimuli involved Chinese features that varied in the number of strokes or involved Ethiopic features unfamiliar to both groups. Chinese pseudocharacters (two radicals) had half the strokes of Chinese pseudowords (two characters). The response terms were English words familiar to both groups. English speakers performed equivalently with the Ethiopic and pseudocharacters, but much worse on the pseudowords. In contrast, Chinese speakers performed equivalently with pseudowords or pseudocharacters, but worse with Ethiopic cues. Experiment 2 showed that the lack of a complexity effect for Chinese speakers was not due to greater ease of rehearsal of pseudowords compared with pseudocharacters. Experiment 3 ruled out that Chinese speakers are just better at learning paired associates involving Mandarin by demonstrating that while complexity did not affect them, other features of the stimuli did. Taken together, it appears that complexity is not an absolute property based on the number of visual elements, but rather a relative property affected by one's prior knowledge.

Retrieval Practice Facilitates Judgments of Learning Through Multiple Mechanisms: Simultaneous and Independent Contribution of Retrieval Confidence and Retrieval Fluency.

Prior studies have shown that predictions of subsequent performance (i.e., Judgments of Learning, JoLs) following tests are more accurate than those following re-study and have suggested that retrieval practice allows people to base their predictions on the current retrieval outcomes so that they assign a higher likelihood of remembering to answers with high confidence. We speculated that other mechanisms, such as retrieval fluency during tests, might also be important for JoLs and that they both offer diagnostic information helping learners to make more accurate JoLs. In the present study, we asked participants to study word-pairs and undergo either a test or re-study trial. Two testing formats (cued-recall and multiple-choice) were administrated for the test condition in two experiments. After the initial test or re-study of the word-pair, participants rated their confidence in the current retrieval accuracy (test) or confidence in acquisition (re-study), followed by a JoL rating where participants predicted their performance in the final test one day later. The results of both experiments showed that the correlation between JoL ratings and the final accuracy was higher for test trials compared with re-study trials. Moreover, using mediation analyses, we found that this high correspondence was only partially mediated by participants' confidence in initial tests. Both retrieval reaction time and retrieval confidence simultaneously mediated the correspondence between JoLs and the final accuracy, suggesting that participants were able to correctly base their JoLs on multiple sources of information that are made available through retrieval practice.

Confidence in accuracy moderates the benefits of retrieval practice.

The effect of Retrieval Practice refers to the phenomenon that taking a practice test is more effective for learning than re-study, probably due to the benefit from processes underlying successful retrievals during practice. However, it is rarely studied whether other processes (e.g., metacognitive monitoring) during retrieval practice may also play an important role. In two experiments, we examined whether the effectiveness of retrieval was affected by subjects' confidence in their retrieval success. Subjects studied word-pairs and rated their confidence after each practice test trial (cued-recall in Exp.1, multiple choice in Exp.2), or re-study trial. In both experiments, we observed the classic retrieval practice effect. Moreover, in Exp.2, the benefits differed as a function of subjects' confidence in their retrieval performance: the effect of retrieval practice only emerged for high-confidence trials with higher than 56% confidence. In summary, the retrieval practice only facilitates the retention of correct answers with high confidence.

The two processes underlying the testing effect- Evidence from Event-Related Potentials (ERPs).

Theoretical explanations of the testing effect (why people learn better from a test than a re-study) have largely focused on either the benefit of attempting to retrieve the answer or on the benefit of re-encoding the queried information after a successful retrieval. While a less parsimonious account, prior neuroimaging evidence has led us to postulate that both of these processes contribute to the benefit of testing over re-study. To provide further empirical support for our position, we recorded ERPs while subjects attempted to recall the second word of a pair when cued with the first. These ERPs were analyzed based on the current response accuracy and as a function of accuracy on the subsequent test, yielding three groups: the first and second tests were correct, the first was correct and the second was not, both were incorrect. Mean amplitude waveforms during the first test showed different patterns depending on the outcome patterns: Between 400 and 700 ms the amplitudes were most positive when both tests were correct and least positive when both were incorrect; mean amplitudes between 700 and 1000 ms only differed as a function of subsequent memory. They were more positive when the second test was correct. Importantly, the later component only predicted subsequent memory when the answers were not overlearned, i.e. only correctly recalled once previously. We interpret the 400-700 ms time window as a component reflecting a retrieval attempt process, which differs as a function of both current and subsequent accuracy, and the later time window as a component reflecting a re-encoding process, which only involves learning from tests, both of which are involved in the testing effect.

fMRI exploration of pedagogical benefits of repeated testing: when more is not always better.

INTRODUCTION: The testing effect refers to superior retention when study is followed by a test rather than followed by another study. Most research to date on why the testing effect occurs has been behavioral, but we employed neuroimaging methods in this study in order to shed light on the underlying processes. METHODS: Subjects were scanned while studying, restudying, and taking cued-recall tests of word pairs (with no feedback). We analyzed the BOLD responses by back sorting the encoding and test trials based on whether the subsequent test was correct or incorrect. We compared the subsequent memory patterns in initial study, restudy, and test trials. RESULTS: Overall, brain activity during test trials was a better predictor of later performance than brain activity during restudy trials. For test trials, we separately examined brain regions associated with the retrieval attempt process during successful retrieval and regions associated with the re-encoding process during retrieval in terms of prediction of subsequent memory. Regions associated with retrieval attempts were found to always predict subsequent memory success (the greater the activation, the more likely the correct recall); however, the regions associated with re-encoding would sometimes predict subsequent failure, specifically when subjects had correctly recalled the associated word several times already. CONCLUSIONS: These results suggest that whether a testing effect advantage is observed depends on both on the retrieval process and the re-encoding process which follows that retrieval.

Building knowledge requires bricks, not sand: The critical role of familiar constituents in learning.

Despite vast efforts to better understand human learning, some principles have been overlooked; specifically, that less familiar stimuli are more difficult to combine to create new knowledge and that this is because less familiar stimuli consume more working memory resources. Participants previously unfamiliar with Chinese characters were trained to discriminate visually similar characters during a visual search task over the course of a month, during which half of the characters appeared much more frequently. Ability to form associations involving these characters was tested via cued recall for novel associations consisting of two Chinese characters and an English word. Each week performance improved on the cued-recall task. Crucially, however, even though all Chinese character pairs were novel each week, those pairs consisting of more familiar characters were more easily learned. Performance on a working-memory task was better for more familiar stimuli, consistent with the claim that familiar stimuli consume fewer working memory resources. These findings have implications for optimal instruction, including second language learning.

Uncovering the neural mechanisms underlying learning from tests.

People learn better when re-study opportunities are replaced with tests. While researchers have begun to speculate on why testing is superior to study, few studies have directly examined the neural underpinnings of this effect. In this fMRI study, participants engaged in a study phase to learn arbitrary word pairs, followed by a cued recall test (recall second half of pair when cued with first word of pair), re-study of each pair, and finally another cycle of cued recall tests. Brain activation patterns during the first test (recall) of the studied pairs predicts performance on the second test. Importantly, while subsequent memory analyses of encoding trials also predict later accuracy, the brain regions involved in predicting later memory success are more extensive for activity during retrieval (testing) than during encoding (study). Those additional regions that predict subsequent memory based on their activation at test but not at encoding may be key to understanding the basis of the testing effect.

An attentional-adaptation account of spatial negative priming: evidence from event-related potentials.

Negative priming (NP) refers to a slower response to a target stimulus if it has been previously ignored. To examine theoretical accounts of spatial NP, we recorded behavioral measures and event-related potentials (ERPs) in a target localization task. A target and distractor briefly appeared, and the participant pressed a key corresponding to the target's location. The probability of the distractor appearing in each of four locations varied, whereas the target appeared with equal probabilities in all locations. We found that response times (RTs) were fastest when the prime distractor appeared in its most probable (frequent) location and when the prime target appeared in the location that never contained a distractor. Moreover, NP effects varied as a function of location: They were smallest when targets followed distractors in the frequent distractor location-a finding not predicted by episodic-retrieval or suppression accounts of NP. The ERP results showed that the P2, an ERP component associated with attentional orientation, was smaller in prime displays when the distractor appeared in its frequent location. Moreover, no differences were apparent between negative-prime and control trials in the N2, which is associated with suppression processes, nor in the P3, which is associated with episodic retrieval processes. These results indicate that the spatial NP effect is caused by both short- and long-term adaptation in preferences based on the history of inspecting unsuccessful locations. This article is dedicated to the memory of Edward E. Smith, and we indicate how this study was inspired by his research career.