How do we perform backward serial recall?

Aging Processes of Working Memory in Different Modalities

Background: Working memory (WM) involves temporarily storing and manipulating information. Research on the impact of aging on WM has shown inconsistent results regarding the decline in visual and verbal WM, with a lack of studies on tactile WM. This study aimed to assess the effects of aging on WM across verbal, visuospatial, and tactile modalities using span tasks of forward (storage) and backward (manipulation) stages. Methods: A total of 130 participants, divided into four age groups of 20-29, 60-69, 70-79, and 80-89, completed the Digit, Visuospatial, and Tactual Spans. Performance was analyzed using a 3 (Task) × 4 (Group) × 2 (Stage) mixed design repeated measures ANOVA. Results: The analysis revealed significant main effects for modality (p < 0.001, ηp2 = 0.15), age (p < 0.001, ηp2 = 0.48), and stage (p < 0.001, ηp2 = 0.30). Digit Span outperformed the other modalities, while Tactual Span showed the worst performance. Additionally, task performance declined with age, and the forward stage was superior to the backward stage. Interaction effects indicated that Digit Span was less affected by aging compared to the Visuospatial and Tactual Spans (p = 0.004, ηp2 = 0.07). Post hoc analyses further revealed that the Digit Span consistently outperformed the other modalities in both stages, with more pronounced differences observed in the forward stage. Conclusions: Verbal WM is more resilient to aging compared to the other modalities while tactile WM declines with age in a manner similar to verbal and visuospatial WM, suggesting a modality-specific impact of aging on WM.

Evidence for separate backward recall and n-back working memory factors: a large-scale latent variable analysis

Multiple studies have explored the factor structure of working memory (WM) tasks, yet few have done so controlling for both the domain and category of the memory items in a single study. In the current pre-registered study, we conducted a large-scale latent variable analysis using variant forms of n-back and backward recall tasks to test whether they measured a single underlying construct, or were distinguished by stimuli-, domain-, or paradigm-specific factors. Exploratory analyses investigated how the resulting WM factor(s) were linked to fluid intelligence. Participants (N = 703) completed a fluid reasoning test and multiple n-back and backward recall tasks containing memoranda that varied across (spatial or verbal material) and within (verbal digits or letters) domain, allowing the variance specific to task content and paradigm to be assessed. Two distinct but related backward recall and n-back constructs best captured the data, in comparison to other plausible model constructions (single WM factor, two-factor domain, and three-factor materials models). Common variance associated with WM was a stronger predictor of fluid reasoning than a residual n-back factor, but the backward recall factor predicted fluid reasoning as strongly as the common WM factor. These data emphasise the distinctiveness between backward recall and n-back tasks.

Forward versus backward recall: Modality testing

OBJECTIVES

One of the most frequently applied paradigms in the clinical and experimental fields for assessing working memory is the simple span task, composed of forward and backward recall conditions. However, the utility of the simple span measures and their relation to working memory modalities has yet to be elucidated. The current study aimed to address which of the span measures is more sensitive to the differentiation between forward and backward recall in the tactile, verbal, and visuo-spatial modalities, and to test if working memory modalities differ in the disparity between the two conditions.

METHODS

134 healthy young adults performed the Tactual, Digit, and Visuo-spatial Span tasks, producing Total Correct scores and Longest Sequence score measures.

RESULTS

There was an interaction effect for condition and modality type, showing better performance for the forward compared to the backward recall in both measures. However, the effect size of the Longest Sequence score was significantly higher than the Total Correct score in all tasks. Furthermore, the Visuo-spatial Span exhibited a larger difference between forward and backward recall compared to the Digit and Tactual Span, whereas no difference was found between the latter two.

CONCLUSIONS

Forward and backward recall are distinguished in all three modalities, and the Longest Sequence score is more sensitive to differentiate between storage and manipulation components of working memory than the Total Correct score. Additionally, the cognitive demand imposed by manipulation compared to storage is the greatest in the visuo-spatial modality.

Asymmetric negative transfer effects of working memory training

Gathercole et al. (Journal of Memory and Language, 105, 19-42, 2019) presented a cognitive routine framework for explaining the underlying mechanisms of working memory (WM) training and transfer. This framework conceptualizes training-induced changes as the acquisition of novel cognitive routines similar to learning a new skill. We further infer that WM training might not always generate positive outcomes because previously acquired routines may affect subsequent task performance in various ways. Thus, the present study aimed to demonstrate the negative effects of WM training via two experiments. We conducted Experiment 1 online using a two-phase training paradigm with only three training sessions per phase and replicated the key findings of Gathercole and Norris (in prep.) that training on a backward circle span task (a spatial task) transferred negatively to subsequent training on a backward letter span task (a verbal task). We conducted Experiment 2 using a reversed task order design corresponding to Experiment 1. The results indicated that the transfer from backward letter training to backward circle training was not negative, but rather weakly positive, suggesting that the direction of the negative transfer effect is asymmetric. The present study therefore found that a negative transfer effect can indeed occur under certain WM training designs. The presence of this asymmetric effect indicates that backward circle and backward letter tasks require different optimal routines and that the locus of negative transfer might be the acquisition process of such optimal routines. Hence, the routines already established for backward circle might hinder the development of optimal routines for backward letter, but not vice versa.

Self-generated strategies in the phonological similarity effect

Strategy use is an important source of individual differences during immediate serial reconstruction. However, not all strategies are equally suited for all tasks. Therefore, assessing participants' dynamic strategy selection across contexts is an important next step for reliable interpretation of individual differences in short-term memory span - in both experimental and clinical settings. Strategy use during reconstruction of phonologically similar and phonologically distinct word sets was directly assessed using a self-report questionnaire. In two experiments, participants reported consistent use of phonological strategies across word sets; however, participants reported additionally using non-phonological strategies (i.e., mental imagery and sentence generation) when tasked with remembering phonologically similar words. In particular, strategy selection was most impacted when the phonologically similar word set was either the only word set or the first word set participants received. When the phonologically similar lists were presented after a classic list of phonologically distinct words, participants continued using the phonological strategies that had been effective for the distinct lists. Moreover, in both experiments, accuracy of phonologically similar lists was better predicted by use of non-phonological strategies than use of phonological strategies. Specifically, reported use of verbalization or rehearsal did not predict accuracy, but participants who reported regularly using mental imagery and/or sentence generation (typically in conjunction with rehearsal) displayed greater serial memory for similar words. These results do not undermine the general assumptions of the phonological similarity effect, but they do indicate that its interpretation is less straightforward than previously thought.

Serial attention to serial memory: The psychological refractory period in forward and backward cued recall

Guided by the conjecture that memory retrieval is attention turned inward, we examined serial attention in serial memory, combining the psychological refractory period (PRP) procedure from attention research with cued recall of two items from brief six-item lists. We report six experiments showing robust PRP effects in cued recall from memory (1-4) and cued report from perceptual displays (5-6), which suggest that memory retrieval requires the same attentional bottleneck as "retrieval" from perception. There were strong direction effects in each memory experiment. Response time (RT) was shorter and accuracy was higher when the cues occurred in the forward direction (left-to-right, top-to-bottom, first-to-last), replicating differences between forward and backward serial recall. Cue positions had strong effects on RT and accuracy in the memory experiments (1-4). The pattern suggested that subjects find cued items in memory by stepping through the list from the beginning or the end, with a preference for starting at the beginning. The perceptual experiments (5-6) showed weak effects of position that were more consistent with direct access. In all experiments, the distance between the cues in the list (lag) had weak effects, suggesting that subjects searched for each cue from the beginning or end of the list more often than they moved through the list from the first cue to the second. Direction, distance, and lag effects on RT and inter-response interval changed with SOA in a manner that suggested they affect bottleneck or pre-bottleneck processes that create and execute a plan for successive retrievals. We conclude that sequential retrieval from memory and sequential attention to perception engage the same computations and we show how computational models of memory can be interpreted as models of attention focused on memory.

Lexical access speed and the development of phonological recoding during immediate serial recall

A recent Registered Replication Report (RRR) of the development of verbal rehearsal during serial recall (Elliott et al., 2021) revealed that children verbalized at younger ages than previously thought (Flavell et al., 1966), but did not identify sources of individual differences. Here we use mediation analysis to reanalyze data from the 934 children ranging from 5 to 10 years old from the RRR for that purpose. From ages 5 to 7, the time taken for a child to label pictures (i.e. isolated naming speed) predicted the child's spontaneous use of labels during a visually-presented serial reconstruction task, despite no need for spoken responses. For 6- and 7-year-olds, isolated naming speed also predicted recall. The degree to which verbalization mediated the relation between isolated naming speed and recall changed across development. All relations dissipated by age 10. The same general pattern was observed in an exploratory analysis of delayed recall for which greater demands are placed on rehearsal for item maintenance. Overall, our findings suggest that spontaneous phonological recoding during a standard short-term memory task emerges around age 5, increases in efficiency during the early elementary school years, and is sufficiently automatic by age 10 to support immediate serial recall in most children. Moreover, the findings highlight the need to distinguish between phonological recoding and rehearsal in developmental studies of short-term memory.

Backward recall and foreknowledge of recall direction: a test of the Encoding-Retrieval Matching Hypothesis

When participants must recall a sequence of items in reverse order just after their presentation, inconsistent findings have been observed relative to when participants must recall a sequence in their presentation order. Recently, the Encoding-Retrieval Matching Hypothesis (ERM) has been developed to account for these inconsistencies. Within the ERM hypothesis, foreknowledge of recall direction plays an important role. In two experiments, we tested a key prediction of the ERM hypothesis: In backward recall with foreknowledge of recall direction, the size of the effect will vary as a function of its reliance on visuospatial representations. Participants performed an immediate serial recall task with digits. As predicted, the detrimental effect of manual-spatial tapping was larger in backward recall relative to forward recall when recall direction was predictable (Experiment 1b), but not when it was unpredictable (Experiment 1a). In Experiment 2, the word length effect, not relying on visuospatial representations, was equally large in forward and backward recall, and it was unaffected by foreknowledge of recall direction. Overall, the results support the predictions derived from the ERM hypothesis and contribute to the delineation of when and how foreknowledge can influence backward recall performance relative to forward recall performance.

Cognitive Dimensions of Learning in Children With Problems in Attention, Learning, and Memory

A data-driven, transdiagnostic approach was used to identify the cognitive dimensions linked with learning in a mixed group of 805 children aged 5 to 18 years recognised as having problems in attention, learning and memory by a health or education practitioner. Assessments included phonological processing, information processing speed, short-term and working memory, and executive functions, and attainments in word reading, spelling, and maths. Data reduction methods identified three dimensions of phonological processing, processing speed and executive function for the sample as a whole. This model was comparable for children with and without ADHD. The severity of learning difficulties in literacy was linked with phonological processing skills, and in maths with executive control. Associations between cognition and learning were similar across younger and older children and individuals with and without ADHD, although stronger links between learning-related problems and both executive skills and processing speed were observed in children with ADHD. The results establish clear domain-specific cognitive pathways to learning that distinguish individuals in the heterogeneous population of children struggling to learn.

Temporal grouping and direction of serial recall

When lists are presented with temporal pauses between groups of items, participants' response times reiterate those pauses. Accuracy is also increased, especially at particular serial positions. By comparing forward with backward serial recall, we tested whether the influence of temporal grouping is primarily a function of serial position or output position. Results favored the latter, both when recall direction was known to participants prior to (Experiment 2) or only after (Experiment 2) studying each list. Alongside fits of variants of a temporal distinctiveness-based model, our findings suggest that the influence of temporal grouping is not just a consequence of grouping information stored during the study phase. Rather, it critically depends on participants cueing with within-chunk position during recall, combined with response suppression.

Strategy Use on Clinical Administrations of Short-Term and Working Memory Tasks

Experimental measures of working memory that minimize rehearsal and maximize attentional control best predict higher-order cognitive abilities. These tasks fundamentally differ from clinically administered span tasks, which do not control strategy use. Participants engaged in concurrent articulation (to limit rehearsal) or concurrent tapping (to limit attentional refreshing) during forward and backward serial recall with each of three distinct stimulus sets: digits, line drawings of common objects, and images of nonsense symbols. The span tasks used common clinical stopping and scoring procedures. Scores were highest for digits and lowest for novel symbols in all combinations of direction and concurrent task. Furthermore, concurrent articulation and concurrent tapping interfered with backward recall to the same degree. Together, these findings indicate that clinically administered immediate serial recall tasks depend on both rehearsal and long-term lexical knowledge making it difficult to use these tasks to separate problems in language ability from problems in attention.

The effects of transcranial direct current stimulation on within- and cross-paradigm transfer following multi-session backward recall training

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Randomised controlled trial combining backward recall memory training and tDCS.

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Systematic investigation into task features constraining training transfer.

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Measurement of potential benefits of tDCS for training and for transfer across tasks with varying degrees of overlap with training task.

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Training transfer is constrained by paradigm but not task materials.

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tDCS over left DLPFC (1 mA, 10 min) does not enhance training or transfer.

Transcranial direct current stimulation (tDCS) has been shown to enhance the efficacy and generalisation of working memory (WM) training, but there has been little systematic investigation into how coupling task-specific WM training with stimulation impacts more specifically on transfer to untrained tasks. This randomised controlled trial investigated the boundary conditions to transfer by testing firstly whether the benefits of training on backward digit recall (BDR) extend to untrained backward recall tasks and n-back tasks with different materials, and secondly which, if any, form of transfer is enhanced by tDCS. Forty-eight participants were allocated to one of three conditions: BDR training with anodal (10 min, 1 mA) or sham tDCS, or visual search training with sham tDCS, applied over the left dorsolateral prefrontal cortex. Transfer was assessed on within- (backward recall with digits, letters, and spatial locations) and cross-paradigm (n-back with digits and letters) transfer tests following three sessions of training and stimulation. On-task training gains were found, with transfer to other backward span but not n-back tasks. There was little evidence that tDCS enhanced on-task training or transfer. These findings indicate that training enhances paradigm-specific processes within WM, but that tDCS does not enhance these gains.

The time course of updating in running span

Running span can be performed by either passively listening to memory items or actively updating the target set. Previous research suggests that the active updating process is demanding and time consuming and is favored at slow rates of presentation while the passive strategy is employed at fast rates. Two experiments examined the time course of recruitment of resources during task performance and its sensitivity to presentation rate. In Experiment 1, participants performed 1 of 3 serial recall tasks: running span, simple span, and modified span. The tasks were completed at the same time as a choice reaction time (RT; CRT) task and the RTs were used to index the resource demands of the memory task. Running span generated higher RT costs than simple span. The costs were present only for positions at and beyond the point in the sequence when the target memory set was changed, indicating a shift to a more cognitively demanding mode of updating. At these positions there was a generalized increase in RT costs that peaked 1,000 ms following item presentation. In Experiment 2 the resource demands of running span varied with presentation rate and a peak demand at 1,000 ms was again evident, but only with a slow presentation rate. In conjunction with strategy reports, these data establish that the process of active updating in running span is slow and cognitively demanding, making it difficult to use when presentation rates are fast.

Working memory training involves learning new skills

We present a new framework characterizing training-induced changes in WM as the acquisition of novel cognitive routines akin to learning a new skill. Predictions were tested in three studies analyzing the transfer between WM tasks following WM training. Study 1 reports a meta-analysis establishing substantial transfer when trained and untrained tasks shared either a serial recall, complex span or backward span paradigm. Transfer was weaker for serial recall of verbal than visuo-spatial material, suggesting that this paradigm is served by an existing verbal STM system and does not require a new routine. Re-analysis of published WM training data in Study 2 showed that transfer was restricted to tasks sharing properties proposed to require new routines. In a re-analysis of data from four studies, Study 3 demonstrated that transfer was greatest for children with higher fluid cognitive abilities. These findings suggest that development of new routines depends on general cognitive resources and that they can only be applied to other similarly-structured tasks.