Implicit temporal tuning of working memory strategy during cognitive skill acquisition

Complex cognitive tasks such as multiple-step arithmetic entail strategies for coordinating mental processes such as calculation with processes for managing working memory (WM). Such strategies must be sensitive to factors such as the time needed for calculation. In 2 experiments we tested whether people can learn the timing constraints on WM demands when those constraints are implicitly imposed. We varied the retention period for intermediate results using the well-known digit size effect: The larger the operands, the longer it takes to perform addition. During learning participants practiced multiple-step arithmetic routines combined with large or small digits. At transfer, they performed both practiced and novel combinations. Practice performance was affected by digit size and WM demands. However, the transfer performance was not fully explained by the digit size effect or the practice effect. We argue that participants acquired temporal tuning of the WM strategy to the implicit retention interval imposed by the digit size and kept using the tuning mode to unpracticed data set.     

加工速度、工作记忆与数字推理能力的发展

本研究得出在数字推理能力的发展过程中加工速度和工作记忆发挥着重要的作用,其中工作记忆对数字推理能力的发展的作用大于加工速度。加工速度可能是年龄与工作记忆的中介,加工速度可能仅对工作记忆的发展起一种直接调节作用,工作记忆对数字推理能力的发展可能起直接调节作用,在数字推理能力的发展过程中工作记忆比加工速度可能发挥着更直接、更一般的作用。     

数学焦虑对工作记忆子系统及数学心算的影响分析

本研究从工作记忆容量的角度入手,探讨数学焦虑对工作记忆子系统及数学心算成绩的影响,并寻求三者之间关系的理论解释。本研究为3×2×2混合实验设计,即三组被试（高、中、低数学焦虑组）、工作记忆两个子系统（言语工作记忆和视空间工作记忆）和两种数学心算任务难度,并记录数学心算的反应时和正确率作为其成绩指标。结果表明在要求较高工作记忆容量的数学心算任务中,数学焦虑通过言语工作记忆和视空间工作记忆都会对数学心算成绩产生影响,其中视空间工作记忆是数学焦虑与复杂数学心算反应时之间的中介变量。     

Developmental functions for speeds of cognitive processes

In Experiment 1, 8- to 21-year-olds were tested on a visual search task in which they determined whether a target digit was present in a set of one to five digits and a memory search task in which they determined whether a target digit was a member of a previously presented set of one to five digits. Increases with age in speeds of visual and memory search were both described well by exponential functions, and the rate of developmental change was similar for the two processes. In Experiment 2, 8- to 22-year-olds were tested on a memory search task, a mental rotation task in which they judged whether a stimulus presented in various orientations was a letter or a mirror image of a letter, an analogical reasoning task in which they judged whether sets of pictures were related to one another according to the same rule, and a mental addition task in which they judged the accuracy of problems such as 2 + 3 = 6. Here, too, for three of the four tasks developmental change was described well by exponential functions with a common rate of change. Results are interpreted in terms of a central mechanism that limits speeded performance and that changes with age.     

Memory skills mediating superior memory in a world-class memorist

Laboratory studies have investigated how individuals with normal memory spans attained digit spans over 80 digits after hundreds of hours of practice. Experimental analyses of their memory skills suggested that their attained memory spans were constrained by the encoding time, for the time needed will increase if the length of digit sequences to be memorised becomes longer. These constraints seemed to be violated by a world-class memorist, Feng Wang (FW), who won the World Memory Championship by recalling 300 digits presented at 1 digit/s. In several studies we examined FW’s memory skills underlying his exceptional performance. First FW reproduced his superior memory span of 200 digits under laboratory condition, and we obtained his retrospective reports describing his encoding/retrieval processes (Experiment 1). Further experiments used self-paced memorisation to identify temporal characteristics of encoding of digits in 4-digit clusters (Experiment 2), and explored memory encoding at presentation speeds much faster than 1 digit/s (Experiment 3). FW’s superiority over previous digit span experts is explained by his acquisition of well-known mnemonic techniques and his training that focused on rapid memorisation. His memory performance supports the feasibility of acquiring memory skills for improved working memory based on storage in long-term memory.     

Midazolam amnesia and short-term/working memory processes

We examined whether midazolam impairs short-term/working memory processes. We hypothesize that prior dissociations in midazolam's effects on short-term/working memory tasks and episodic memory tasks arise because midazolam has a larger effect on episodic memory processes than on short-term/working memory processes. To examine these issues, .03 mg/kg of participant's bodyweight of midazolam was administered in a double-blind placebo-controlled within-participant design. Performance on the digit span and category generation/recall tasks was examined. The results of Experiment 1 demonstrated that: (1) midazolam impaired performance on the digit span task; (2) midazolam did not impair performance on the category generation task; (3) midazolam impaired performance on the category recall task; and (4) midazolam's effect on category recall was four times as large as its effect on digit span. The results of Experiment 2 demonstrated that midazolam did not impair digit span performance when the digit span task was administered at a later time. These results suggest that midazolam can impair short-term/working memory processes, but these effects are substantially smaller than midazolam's effect on episodic memory processes. Moreover, they demonstrate that conscious awareness of materials during study is not sufficient to produce episodic memory.     

心算形式对不同近似数量系统敏锐度儿童心算表现的影响

选取112名二年级小学生,以点阵比较任务测量近似数量系统敏锐度,同时以工作记忆测验成绩为协变量,探究了不同心算形式（视算、读算）对不同近似数量系统敏锐度儿童心算表现的潜在影响。结果显示：（1）心算形式显著影响心算的正确率,读算形式下儿童的心算表现最好;（2）控制工作记忆影响后,心算形式与近似数量系统敏锐分组均对心算正确率影响显著。总体来讲,读算可能是提高小学儿童简单心算表现的有效形式,并能提高低近似数量系统敏锐度儿童的心算表现。     

State-Space Analysis of Working Memory in Schizophrenia: An FBIRN Study

The neural correlates of working memory (WM) in schizophrenia (SZ) have been extensively studied using the multisite fMRI data acquired by the Functional Biomedical Informatics Research Network (fBIRN) consortium. Although univariate and multivariate analysis methods have been variously employed to localize brain responses under differing task conditions, important hypotheses regarding the representation of mental processes in the spatio-temporal patterns of neural recruitment and the differential organization of these mental processes in patients versus controls have not been addressed in this context. This paper uses a multivariate state-space model (SSM) to analyze the differential representation and organization of mental processes of controls and patients performing the Sternberg Item Recognition Paradigm (SIRP) WM task. The SSM is able to not only predict the mental state of the subject from the data, but also yield estimates of the spatial distribution and temporal ordering of neural activity, along with estimates of the hemodynamic response. The dynamical Bayesian modeling approach used in this study was able to find significant differences between the predictability and organization of the working memory processes of SZ patients versus healthy subjects. Prediction of some stimulus types from imaging data in the SZ group was significantly lower than controls, reflecting a greater level of disorganization/heterogeneity of their mental processes. Moreover, the changes in accuracy of predicting the mental state of the subject with respect to parametric modulations, such as memory load and task duration, may have important implications on the neurocognitive models for WM processes in both SZ and healthy adults. Additionally, the SSM was used to compare the spatio-temporal patterns of mental activity across subjects, in a holistic fashion and to derive a low-dimensional representation space for the SIRP task, in which subjects were found to cluster according to their diagnosis.     

Correlation of motor skill,mental rotation,and working memory in 3- to 6-year-old children

A relationship between motor processes and mental rotation has been suggested by current research; however, the influence of working memory on this relationship has not yet been determined. Therefore, a correlation between motor tests, paper–pencil and chronometric mental rotation tests, and working memory tests were conducted in 3- to 6-year-old children. A stepwise multiple-regression showed that 55.5% of the variance was explained by the working memory tests: digit span forward and Corsi forward. This indicates that working memory and executive functions may play an important role in mental rotation and motor processes.     

The relationship between mental rotation and arithmetic: do number line estimation,working memory,or place-value concept matter?

Mental rotation is positively related to arithmetic ability; however, the mechanism underlying this relationship remains unclear. The possible roles of working memory, place-value concept, and number line estimation in the correlation between mental rotation and whole-number computation were investigated. One hundred and fifty-five first-grade students were tested to determine their mental rotation ability, arithmetic ability, and non-verbal intelligence. One year later, their working memory, place-value concept, number line estimation, and overall arithmetic ability were assessed. After controlling for age, gender, and prior arithmetic ability, we found that mental rotation uniquely predicted arithmetic ability after one year. Further mediation analyses demonstrated that number line estimation significantly mediated the relationship between mental rotation and arithmetic ability. In contrast, neither working memory nor place-value concept significantly mediated the relationship between mental rotation and arithmetic ability. This study highlights that mental number line estimation is the most important element explaining the influence of a dynamic spatial skill, that is, mental rotation, on arithmetic ability among young Chinese children.     

Visuospatial and verbal memory in mental arithmetic

Working memory allows complex information to be remembered and manipulated over short periods of time. Correlations between working memory and mathematics achievement have been shown across the lifespan. However, only a few studies have examined the potentially distinct contributions of domain-specific visuospatial and verbal working memory resources in mental arithmetic computation. Here we aimed to fill this gap in a series of six experiments pairing addition and subtraction tasks with verbal and visuospatial working memory and interference tasks. In general, we found higher levels of interference between mental arithmetic and visuospatial working memory tasks than between mental arithmetic and verbal working memory tasks. Additionally, we found that interference that matched the working memory domain of the task (e.g., verbal task with verbal interference) lowered working memory performance more than mismatched interference (verbal task with visuospatial interference). Findings suggest that mental arithmetic relies on domain-specific working memory resources.     

Susceptibility of spatial and verbal working memory to demands of the central executive

We used a dual-task paradigm to examine the degree to which domain-specific spatial and verbal subsystems depend on the domain-general central executive. Forty participants were asked to retain spatial or verbal information while performing a concurrent secondary task related to simple arithmetic. The secondary tasks consisted of three cognitive processes: single-digit addition, a digit-carrying operation, and digit reading. The single-digit addition and carry operation include central executive functioning, while digit reading relies solely on the phonological loop. The single-digit addition caused a performance decrement on the spatial working memory task, while the digit reading impaired performance on the verbal working memory task. The carry operation interfered with recall accuracy on both working memory tasks. The spatial working memory task was significantly correlated with the verbal working memory task only when the secondary task was more demanding on the central executive. Our results suggest that spatial working memory rather than verbal working memory is susceptible to failure of central executive functioning and that the central executive plays an important role in regulating the cognitive demands of different domains.     

Interference due to shared features between action plans is influenced by working memory span

In this study, we examined the interactions between the action plans that we hold in memory and the actions that we carry out, asking whether the interference due to shared features between action plans is due to selection demands imposed on working memory. Individuals with low and high working memory spans learned arbitrary motor actions in response to two different visual events (A and B), presented in a serial order. They planned a response to the first event (A) and while maintaining this action plan in memory they then executed a speeded response to the second event (B). Afterward, they executed the action plan for the first event (A) maintained in memory. Speeded responses to the second event (B) were delayed when it shared an action feature (feature overlap) with the first event (A), relative to when it did not (no feature overlap). The size of the feature-overlap delay was greater for low-span than for high-span participants. This indicates that interference due to overlapping action plans is greater when fewer working memory resources are available, suggesting that this interference is due to selection demands imposed on working memory. Thus, working memory plays an important role in managing current and upcoming action plans, at least for newly learned tasks. Also, managing multiple action plans is compromised in individuals who have low versus high working memory spans.     

Phonological and visual working memory in mental addition

The goal of the present research was to examine the role of working memory in mental arithmetic. Adults (n = 96) solved multidigit arithmetic problems (e.g., 52 + 3; 3 + 52) alone and in combination with either a phonological memory load (i.e., nonwords, such as gup) or a visual memory load (i.e., random pattern of asterisks). The participants solved problems presented in a vertical format significantly faster than problems presented in a horizontal format. They also solved double digit first problems (e.g., 52 + 3) more quickly than the reverse (e.g., 3 + 52), but only when the problems were presented horizontally. Performance was worse in the phonological load condition than in the visual load condition for the participants who solved problems presented horizontally, whereas performance was worse in the visual load condition than in the phonological load condition when problems were presented vertically. The present research provides evidence that both phonological and visual aspects of working memory are involved in mental arithmetic but that the role of each working memory component will depend on such factors as presentation format.     

Book reviews

Results from past studies show that the central executive, as conceptualised in the working memory model of Baddeley and Hitch (), plays an important role in simple mental arithmetic. According to this model the central executive is viewed as a unitary system. Recent research, however, suggests that the “central executive” can be fractionated in more autonomous executive functions, such as inhibition, response selection, planning, and input monitoring. In four experiments we studied the role of two possible executive functions (input monitoring and response selection) in solving simple sums. Subjects solved one‐digit sums (e.g., 5 + 7) in a single‐task condition as well as in dual‐task conditions. The results show that secondary tasks, which require a choice, impair the calculation of simple sums. On the other hand, an increased degree of input monitoring in the secondary tasks does not seem to impair the calculation of the sums. These findings show that response selection is strongly involved in simple arithmetic and may be one of the core executive processes in mental arithmetic.     

Counting on working memory in arithmetic problem solving

Mental calculation is an important everyday skill involving access to well-learned procedures, problem solving, and working memory. Although there is an active literature on acquiring concepts and procedures for mental arithmetic, relatively little is known about the role of working memory in this task. This paper reports two experiments in which dual-task methodology is used to study the role of components of working memory in mental addition. In Experiment 1, mental addition of auditorily presented two-digit numbers was significantly disrupted by concurrent random letter generation and, to a lesser extent, by concurrent articulatory suppression, but was unimpaired by concurrent hand movement or by presentation of irrelevant pictures. Although the number of errors increased with two of the dual tasks, the incorrect responses tended to be quite close to the correct answer. In Experiment 2, the numbers for addition were presented visually. Here again, random generation produced the largest disruption of mental arithmetic performance, while a smaller amount of disruption was observed for articulatory suppression, hand movement, and unattended auditorily presented two-digit numbers. The overall levels of performance were better and the absolute size of the disruptive effects shown with visual presentation was very small compared with those found for auditory presentation. This pattern of results is consistent with a role for a central executive component of working memory in performing the calculations required for mental addition and in producing approximately correct answers. Visuospatial resources in working memory may also be involved in approximations. The data support the view that the subvocal rehearsal component of working memory provides a means of maintaining accuracy in mental arithmetic, and this matches a similar conclusion derived from previous work on counting. The general implications for the role of working memory in arithmetic problem solving will be discussed.     

Cross-task cross talk in memory and perception

The application of the additive factors method depends on finding factors that selectively influence processing stages. When all the processes for a task are in series, a factor directly influencing a process might change its output and thereby have indirect influence on succeeding processes. We investigate whether such indirect influence is possible between processes associated with different tasks being performed together. In two dual-task memory scanning and arithmetic experiments with digits as the stimuli for both tasks, information relevant for only one of the tasks nonetheless affected performance of the other. When the same digit was relevant for the two tasks, cross-task facilitation and interference were observed in some cases. Displaying the same digit for both tasks led to relatively fast response times, paralleling the effect of flankers in the response competition paradigm. But repetition of digits in memory slowed responses. It is suggested that the need for control processes to keep task information segregated is responsible for the pattern of effects.     

Memory span as a measure of individual differences in memory capacity

Two experiments were carried out to investigate whether the immediate digit span measure traditionally used in the assessment of individual differences in cognition is a good predictor of performance on other memory tasks. In the first experiment, it was found that subjects’ digit spans were not significantly related to their performances on either short-term or longterm memory tasks, or to theoretical measures of their memory store capacities. Memory for the temporal occurrence of events, however, proved to be positively correlated with digit span. A second experiment confirmed that digit span was correlated with memory for the temporal occurrence of events, but not with item memory. Thus it was concluded that an individual’s digit span reflects his ability to retain information about the order of a sequence of events rather than the capacity of his short- or long-term memory.     

Memory Span for Arabic Numerals and Digit Words: Evidence for a Limited-capacity, Visuo-spatial Storage System

Six experiments examined the determinants of the numeral advantage effect: the finding that memory span for Arabic numerals (1, 2, 3, etc.) is greater than for digit words (one, two, three, etc.). The speed of item identification for numeral and digit words was unrelated to memory span for the same items and a larger memory span for numerals persisted under concurrent random generation (Experiment 1). The numeral advantage, however, was abolished when the items were presented in random locations within an invisible 3x3 grid (Experiment 2) and in locations on a horizontal plane that ran contrary to the natural direction of reading (Experiment 3). When the items were presented in the same location, a disruption of the spatial component of visuo-spatial working memory eliminated the numeral advantage (Experiment 4), whereas interference with the visual component of the system did not (Experiment 5). When the items were spatially distributed in a 3x3 matrix, however, neither visual nor spatial interference abolished the effect (Experiment 6). Taken together, these findings suggest that the numeral advantage effect is mediated by discrete components in visuo-spatial working memory dedicated to the temporary storage and renewal of visual codes and questions the assumption that the underlying mechanisms in immediate, visual serial recall are equivalent between stimulus categories.