Time and resource limits on working memory: cross-age consistency in counting span performance

This longitudinal study separated resource demand effects from those of retention interval in a counting span task among 100 children tested in grade 2 and again in grades 3 and 4. A last card large counting span condition had an equivalent memory load to a last card small, but the last card large required holding the count over a longer retention interval. In all three waves of assessment, the last card large condition was found to be less accurate than the last card small. A model predicting reading comprehension showed that age was a significant predictor when entered first accounting for 26% of the variance, but counting span accounted for a further 22% of the variance. Span at Wave 1 accounted for significant unique variance at Wave 2 and at Wave 3. Results were similar for math calculation with age accounting for 31% of the variance and counting span accounting for a further 34% of the variance. Span at Wave 1 explained unique variance in math at Wave 2 and at Wave 3.     

Arithmetic operation and working memory: differential suppression in dual tasks

The relationship between arithmetic function and working memory was examined using a dual-task paradigm for either phonological or visuo-spatial suppression. Simultaneous phonological rehearsal significantly delayed the performance of multiplication but not subtraction, whereas holding an image in the mind delayed subtraction but not multiplication. This result indicates that arithmetic function is related to working memory in a subsystem-specific manner: multiplication is more closely linked to phonological loop and subtraction to visuo-spatial sketchpad. Whereas this is not compatible with the notion that arithmetic is done on a unitary, amodal representation of numbers, it provides support for the triple-code and/or the modular processing models on human numerical cognition in which number representations are specific for input/output modality and arithmetic types.     

Spatial and visual working memory ability in children with difficulties in arithmetic word problem solving

Although various studies support the multicomponent nature of visuospatial working memory, to date there is no general consensus on the distinction of its components. A difference is usually proposed between visual and spatial components of working memory, but the individual roles of these components in mathematical learning disabilities remains unclear. The present study aimed to examine the involvement of visual and spatial working memory in poor problem-solvers compared with children with normal level of achievement. Fourth-grade participants were presented with tasks measuring phonological loop, central executive, and visual versus spatial memory. In two separate experiments, both designed to distinguish visual and spatial component involvement, poor problem-solvers specifically failed on spatial—but not visual or phonological—working memory tasks. Results are discussed in the light of possible working memory models, and specifically demonstrate that problem-solving ability can benefit from analysis of spatial processes, which involves ability to manipulate and transform relevant information; instead, no benefit is gained from the analysis of visual pictorial detail.     

The influence of working memory on reading growth in subgroups of children with reading disabilities

This 3-year longitudinal study determined whether (a) subgroups of children with reading disabilities (RD) (children with RD only, children with both reading and arithmetic deficits, and low verbal IQ readers) and skilled readers varied in working memory (WM) and short-term memory (STM) growth and (b) whether growth in an executive system and/or a phonological storage system mediated growth in reading performance. A battery of memory and reading measures was administered to 84 children (11-17 years of age) across three testing waves spaced 1 year apart. The results showed that skilled readers yielded higher WM growth estimates than did the RD groups. No significant differentiation among subgroups of children with RD on growth measures emerged. Hierarchical linear modeling showed that WM (controlled attention), rather than STM (phonological loop), was related to growth in reading comprehension and reading fluency. The results support the notion that deficient growth in the executive component of WM underlies RD.     

Working memory and access to numerical information in children with disability in mathematics

The relationship among working memory, mathematic ability, and the cognitive impairment of children with difficulties in mathematics was examined. A group of children with difficulties in mathematics (MD) was compared with a group of children with a normal level of achievement matched for vocabulary, age, and gender (N = 49). The children were required to perform a variety of working memory and short-term memory tasks that had been administered 1 year previously. Moreover, the children were asked to perform tasks designed to provide information about speed of articulation. The results suggest a general working memory deficit in children with MD, specifically in the central executive component of Baddeley's model and primarily in the ability to inhibit irrelevant information. However, the MD children were not impaired in speech rate and counting speed tasks, which mainly involve the role of the articulatory loop.     

Numerical and nonnumerical estimation in children with and without mathematical learning disabilities

There are currently multiple explanations for mathematical learning disabilities (MLD). The present study focused on those assuming that MLD are due to a basic numerical deficit affecting the ability to represent and to manipulate number magnitude (Butterworth, 1999 Butterworth, B. 1999. The mathematical brain, London, , United Kingdom: Macmillan.  [Google Scholar], 2005 Butterworth, B. 2005. “Developmental dyscalculia”. In Handbook of mathematical cognition, Edited by: Campbell, J. I. D. 455–467. New York, NY: Psychology Press.  [Google Scholar]; A. J. Wilson &; Dehaene, 2007 Wilson, A. J. and Dehaene, S. 2007. “Number sense and developmental dyscalculia”. In Human behavior, learning, and the developing brain: Atypical development, 2nd, Edited by: Coch, D., Dawson, G. and Fischer, K. 212–237. New York, NY: Guilford Press.  [Google Scholar]) and/or to access that number magnitude representation from numerical symbols (Rousselle &; Noël, 2007 Rousselle, L. and Noël, M. P. 2007. Basic numerical skills in children with mathematics learning disabilities: A comparison of symbolic vs non-symbolic number magnitude processing. Cognition, 102(3): 361–395. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). The present study provides an original contribution to this issue by testing MLD children (carefully selected on the basis of preserved abilities in other domains) on numerical estimation tasks with contrasting symbolic (Arabic numerals) and nonsymbolic (collection of dots) numbers used as input or output. MLD children performed consistently less accurately than control children on all the estimation tasks. However, MLD children were even weaker when the task involved the mapping between symbolic and nonsymbolic numbers than when the task required a mapping between two nonsymbolic numerical formats. Moreover, in the estimation of nonsymbolic numerosities, MLD children relied more than control children on perceptual cues such as the cumulative area of the dots. Finally, the task requiring a mapping from a nonsymbolic format to a symbolic format was the best predictor of MLD. In order to explain these present results, as well as those reported in the literature, we propose that the impoverished number magnitude representation of MLD children may arise from an initial mapping deficit between number symbols and that magnitude representation.     

The precursors of mathematics learning: Working memory,phonological ability and numerical competence

This research aims at identifying the precursors of mathematics learning at the beginning of primary school. There are few experimental studies on this topic and existing ones use between-subjects designs and correlation analysis. This paper analyses longitudinal data to investigate whether the relationship between basic abilities and mathematics learning is causally interpretable, rather than one where cognitive abilities are correlated to early mathematics learning in a cross-section design.     

Age-related differences in learning disabled and skilled readers' working memory

This study determines whether age-related deficits in learning disabled (LD) readers' working memory performance reflect delays in retrieval efficiency and/or storage capacity. The study compared LD and skilled readers' working memory performance (N=226) across four age groups (7, 10, 13, and 20) for phonological, visual-spatial, and semantic information under initial (non-cued), gain (cues that bring performance to an asymptotic level), and maintenance conditions (asymptotic conditions without cues). The important results were that LD readers' working memory performance was inferior to skilled readers on verbal and visual-spatial working memory tasks across all age groups and these differences increased on gain and maintenance conditions when compared to initial conditions. These reading group differences remained when age, reading, and mathematics were partialed from the analysis. The results support a general capacity explanation of reading group differences that is not totally dependent on reading skill. These differences in capacity reflect demands placed on both the accessing of new information and the maintenance of old information that extend beyond the phonological system.     

Differential constraints on the working memory and reading abilities of individuals with learning difficulties and typically developing children

This study examined the factors that constrain the working memory span performance and reading ability of individuals with generalized learning difficulties. In the study, 50 individuals with learning difficulties (LD) and 50 typically developing children (TD) matched for reading age completed two working memory span tasks. Participants also completed independent measures of the processing and storage operations involved in each working memory span task and Raven's Coloured Progressive Matrices. The results showed that despite an equivalent level of working memory span, the relative importance of the constraints on working memory differed between the groups. In addition, working memory span was not closely related to word recognition or sentence comprehension performance in the LD group. These results suggest that the working memory span performance of LD and TD individuals may reflect different working memory limitations and that individuals with generalized learning difficulties may approach cognitive tasks in a qualitatively different way from that of typically developing individuals.     

Working memory and children's use of retrieval to solve addition problems

This study tested the hypothesis that children with high working memory capacities solve single-digit additions by direct retrieval of the answers from long-term memory more often than do children with low working memory capacities. Counting and reading letter span tasks were administered to groups of third-grade (mean age=107 months) and fourth-grade (mean age=118 months) children who were also asked to solve 40 single-digit additions. High working memory capacity was associated with more frequent use of retrieval and faster responses in solving additions. The effect of span on the use of retrieval increased with the size of the minimum addend. The relation between working memory measures and use and speed of retrieval did not depend on the numerical or verbal nature of the working memory task. Implications for developmental theories of cognitive arithmetic and theories of working memory are discussed.     

Stimulus modality and working memory performance in Greek children with reading disabilities: Additional evidence for the pictorial superiority hypothesis

This study investigated the effects of stimulus presentation modality on working memory performance in children with reading disabilities (RD) and in typically developing children (TDC), all native speakers of Greek. It was hypothesized that the visual presentation of common objects would result in improved learning and recall performance as compared to the auditory presentation of stimuli. Twenty children, ages 10–12, diagnosed with RD were matched to 20 TDC age peers. The experimental tasks implemented a multitrial verbal learning paradigm incorporating three modalities: auditory, visual, and auditory plus visual. Significant group differences were noted on language, verbal and nonverbal memory, and measures of executive abilities. A mixed-model MANOVA indicated that children with RD had a slower learning curve and recalled fewer words than TDC across experimental modalities. Both groups of participants benefited from the visual presentation of objects; however, children with RD showed the greatest gains during this condition. In conclusion, working memory for common verbal items is impaired in children with RD; however, performance can be facilitated, and learning efficiency maximized, when information is presented visually. The results provide further evidence for the pictorial superiority hypothesis and the theory that pictorial presentation of verbal stimuli is adequate for dual coding.     

Basic numerical skills in children with mathematics learning disabilities: a comparison of symbolic vs non-symbolic number magnitude processing

Forty-five children with mathematics learning disabilities, with and without comorbid reading disabilities, were compared to 45 normally achieving peers in tasks assessing basic numerical skills. Children with mathematics disabilities were only impaired when comparing Arabic digits (i.e., symbolic number magnitude) but not when comparing collections (i.e., non-symbolic number magnitude). Moreover, they automatically processed number magnitude when comparing the physical size of Arabic digits in an Stroop paradigm adapted for processing speed differences. Finally, no evidence was found for differential patterns of performance between MD and MD/RD children in these tasks. These findings suggest that children with mathematics learning disabilities have difficulty in accessing number magnitude from symbols rather than in processing numerosity per se.     

Working memory deficits in developmental dyscalculia: The importance of serial order

Although a number of studies suggests a link between working memory (WM) storage capacity of short-term memory and calculation abilities, the nature of verbal WM deficits in children with developmental dyscalculia (DD) remains poorly understood. We explored verbal WM capacity in DD by focusing on the distinction between memory for item information (the items to be retained) and memory for order information (the order of the items within a list). We hypothesized that WM for order could be specifically related to impaired numerical abilities given that recent studies suggest close interactions between the representation of order information in WM and ordinal numerical processing. We investigated item and order WM abilities as well as basic numerical processing abilities in 16 children with DD (age: 8–11 years) and 16 typically developing children matched on age, IQ, and reading abilities. The DD group performed significantly poorer than controls in the order WM condition but not in the item WM condition. In addition, the DD group performed significantly slower than the control group on a numerical order judgment task. The present results show significantly reduced serial order WM abilities in DD coupled with less efficient numerical ordinal processing abilities, reflecting more general difficulties in explicit processing of ordinal information.     

The development of strategy use in elementary school children: working memory and individual differences

The current study tested the development of working memory involvement in children's arithmetic strategy selection and strategy efficiency. To this end, an experiment in which the dual-task method and the choice/no-choice method were combined was administered to 10- to 12-year-olds. Working memory was needed in retrieval, transformation, and counting strategies, but the ratio between available working memory resources and arithmetic task demands changed across development. More frequent retrieval use, more efficient memory retrieval, and more efficient counting processes reduced the working memory requirements. Strategy efficiency and strategy selection were also modified by individual differences such as processing speed, arithmetic skill, gender, and math anxiety. Short-term memory capacity, in contrast, was not related to children's strategy selection or strategy efficiency.     

The relationship between sleep and working memory in children with neurological conditions

The objective of this study is to investigate whether sleep problems might account for the increased working memory deficits observed in school-aged children with neurological conditions. A novel, transdiagnostic approach to the investigation was chosen, and sleep is treated as a process that can potentially account for working memory difficulties across a range of neurological conditions. Prevalence estimates of sleep problems are also examined. Archival data of 237 children aged 6 to 11 years were collected from a Western Australian statewide neuropsychological service for the period 26 July 2011 to 14 January 2014. Measures of parent-reported sleep quality, snoring, and daytime sleepiness were obtained, in addition to objective measures of verbal and spatial working memory, storage capacity, and processing speed. The results of the data analysis reveal that over one third of participants reported having clinically-significant levels of sleep problems and that poor sleep quality is significantly associated with verbal working memory difficulties. This association remains after partialling out the variance contributed to performance by storage capacity and processing speed, suggesting that sleep is impacting upon an executive component of working memory. No other significant associations are observed. The results suggest that poor sleep quality is associated with an executive component of verbal (rather than spatial) working memory in children with neurological conditions. This has implications for the biological mechanisms thought to underlie the relationship between sleep and cognition in children. The results also demonstrate the clinical utility of a transdiagnostic approach when investigating sleep and cognition in children with neurological conditions.     

The trajectory of mathematics skills and working memory thresholds in girls with fragile X syndrome

Fragile X syndrome is a common genetic disorder associated with executive function deficits and poor mathematics achievement. In the present study, we examined changes in math performance during the elementary and middle school years in girls with fragile X syndrome, changes in the working memory loads under which children could complete a cognitive switching task, and the association between these two areas of function, in girls with fragile X syndrome relative to their peers. Our findings indicate that the trajectory of math and executive function skills of girls with fragile X differs from that of their peers and that these skills contribute to predicting math achievement and growth in math performance over time. Also, changes in math performance were associated with incremental increases in working memory demands, suggesting that girls with fragile X have a lower threshold for being able to perform under increasing task demands. Still, we found improvement in executive function performance between 10 and 12 years in girls with fragile X rather than a performance plateau as has been reported in other studies. The findings implicate the importance of early intervention in mathematics for girls with fragile X that addresses poor calculation skills, the supporting numerical skills, and deficits in executive functions, including working memory.     

Identifying the nature of impairments in executive functioning and working memory of children with severe difficulties in arithmetic

An age-matched achievement-matched design was used to examine whether the executive functioning and working memory impairments exhibited by children with severe difficulties in arithmetic (SDA) are better viewed as developmental lags or as cognitive deficits. Three groups of children were included: 20 SDA children, 20 typically achieving children (CM) matched in chronological age with the SDA children, and 20 younger typically achieving children (AM) matched in achievement with the SDA group. While children with SDA did not exhibit impairments in color-word inhibition and verbal working memory, they did demonstrate impairments in shifting, quantity-digits inhibition, and visuospatial working memory. As children with SDA did not perform more poorly than their AM counterparts on any of these tasks, impairments in specific areas of executive functioning and working memory appear to reflect developmental lags rather than cognitive deficits.     

Working memory, reading, and mathematical skills in children with developmental coordination disorder

The aim of the present study was investigate the relationship between working memory and reading and mathematical skills in 55 children diagnosed with developmental coordination disorder (DCD). The findings indicate a pervasive memory deficit in all memory measures. In particular, deficits observed in visuospatial short-term and working memory tasks were significantly worse than in the verbal short-term memory ones. On the basis of these deficits, the sample was divided into high and low visuospatial memory ability groups. The low visuospatial memory group performed significantly worse on the attainment measures compared to the high visuospatial memory group, even when the contribution of IQ was taken into account. When the sample was divided into high and low verbal working memory ability groups, verbal working memory skills made a unique contribution to attainment only when verbal IQ was taken into account, but not when performance IQ was statistically controlled. It is possible that the processing demands of the working memory tasks together with the active motor component reflected in the visuospatial memory tasks and performance IQ subtest both play a crucial role in learning in children with DCD.     

Instruction and load effects on high-skill and low-skill individuals: A study in the domain of mental arithmetic

What happens when people are asked to respond as quickly or as accurately as possible? This study tested the effects of speed/accuracy instructions and working-memory load on people's strategy efficiency and strategy selection. Adult participants solved simple addition problems (Experiment 1) and simple multiplication problems (Experiment 2) under load and no-load conditions and provided trial-by-trial strategy reports. High-skill participants were more efficient than low-skill participants, but the underlying causes of these skill-related effects differed across experiments. In the addition experiment, high-skill participants responded adaptively to the changing situations by changing their strategy choices, which resulted in smaller effects on their actual performance. Low-skill participants in contrast, did not change their strategy choices as adaptively, which resulted in less efficient performance—and especially so under load conditions. In the multiplication experiment, high-skill and low-skill participants differed in strategy efficiencies rather than in strategy choices. In the discussion, the results are further interpreted and future adaptations for the adaptive strategy choice model (ASCM; Siegler & Jenkins, 1989) are suggested.     

Redintegration and the benefits of long-term knowledge in verbal short-term memory: an evaluation of Schweickert's (1993) multinomial processing tree model

The impact of four long-term knowledge variables on serial recall accuracy was investigated. Serial recall was tested for high and low frequency words and high and low phonotactic frequency nonwords in 2 groups: monolingual English speakers and French-English bilinguals. For both groups the recall advantage for words over nonwords reflected more fully correct recalls with fewer recall attempts that consisted of fragments of the target memory items (one or two of the three target phonemes recalled correctly); completely incorrect recalls were equivalent for the 2 list types. However, word frequency (for both groups), nonword phonotactic frequency (for the monolingual group), and language familiarity all influenced the proportions of completely incorrect recalls that were made. These results are not consistent with the view that long-term knowledge influences on immediate recall accuracy can be exclusively attributed to a redintegration process of the type specified in multinomial processing tree model of immediate recall. The finding of a differential influence on completely incorrect recalls of these four long-term knowledge variables suggests instead that the beneficial effects of long-term knowledge on short-term recall accuracy are mediated by more than one mechanism.