Working memory deficits in children with specific learning disorders

This article examines working memory functioning in children with specific developmental disorders of scholastic skills as defined by ICD-10. Ninety-seven second to fourth graders with a minimum IQ of 80 are compared using a 2 x 2 factorial (dyscalculia vs. no dyscalculia; dyslexia vs. no dyslexia) design. An extensive test battery assesses the three subcomponents of working memory described by Baddeley (1986): phonological loop, visual-spatial sketchpad, and central executive. Children with dyscalculia show deficits in visual-spatial memory; children with dyslexia show deficits in phonological and central executive functioning. When controlling for the influence of the phonological loop on the performance of the central executive, however, the effect is no longer significant. Although children with both reading and arithmetic disorders are consistently outperformed by all other groups, there is no significant interaction between the factors dyscalculia and dyslexia.     

Mixture growth models of RAN and RAS row by row: insight into the reading system at work over time

Children (n = 122) and adults (n = 200) with dyslexia completed rapid automatic naming (RAN) letters, rapid automatic switching (RAS) letters and numbers, executive function (inhibition, verbal fluency), and phonological working memory tasks. Typically developing 3rd (n = 117) and 5th (n = 103) graders completed the RAS task. Instead of analyzing RAN/RAS results the usual way (total time), growth mixture modeling assessed trajectories of successive times for naming 10 symbols in each of five rows. For all three samples and both RAN and RAS, two latent classes were identified. The “faster” class performed slowly on the first row and increased time by small increments on subsequent rows. The “slower” latent class performed more slowly on the first row, and children, but not adults, increased time by larger increments on subsequent rows. For children, both the initial row (automaticity index) and slope (sustained controlled processing index) of the trajectory differentiated the classes. For adults, only the initial row separated the classes. The longest time was on row 3 for RAN and row 4 for RAS. For the typically developing 5th graders, close in age to the children with dyslexia, the trajectories were flatter than for children with dyslexia and only the slower class (4%) showed the peak on row 4. For children with dyslexia, inhibition predicted RAN slope within the slower latent class and phonological working memory predicted RAS slope for both latent classes. For adults with dyslexia, inhibition and phonological working memory differentiated both latent classes on RAN intercept and RAS slope. Taken together, RAN, which may assess the phonological loop of working memory, and RAS, which may assess the central executive in working memory, may explain the timing deficit in dyslexia in sustaining coordinated orthographic-phonological processing over time. This research was supported by Grant Ns. P50 33812 and R01 HD25858 from the National Institute of Child Health and Human Development, Virginia W. Berninger, PI.     

学习不良者的工作记忆特点

有关学习不良者的工作记忆特点的研究表明,阅读不良者与数学学习不良者都存在语音回路功能缺陷(如语音表征的效率低)以及中央执行器功能缺陷(如对注意控制的能力不足) ,即学习不良与工作记忆缺陷密切相关。今后的研究应进一步探明学习不良者工作记忆缺陷的深层原因。     

工作记忆与学习能力的关系

工作记忆是一种对信息进行暂时加工和贮存的能量有限的记忆系统,工作记忆通过阅读理解、写作和数学问题解决而影响学生的学习能力。语音回路对阅读的影响更多地体现在复杂句子结构的理解上,中央执行功能在语言意义的加工过程中起着更大的作用,写作能力的逐步完善与工作记忆能力的增长密不可分,工作记忆的三个成分对简单和复杂数学问题解决都产生重要影响。     

Effects of reading and writing on cerebral laterality in good readers and children with dyslexia.

The present study evaluated the idea that the hemisphere-specific cognitive demands of reading and writing may induce task-specific maladaptive patterns of language lateralization in children with dyslexia. Situation-specific lateralization was examined in a repeated measures design under three dichotic listening conditions: baseline, concurrent reading, and concurrent writing. Twelve males with phonological dyslexia, 8 to 12 years old, were compared to 12 age-matched and 12 younger reading-matched good readers. Lateralization patterns were examined for condition-specific relationships to pseudoword decoding, word recognition, reading comprehension, spelling, and arithmetic. The results show that dyslexia is not related to incomplete lateralization or to a failure to inhibit verbal processing in the right hemisphere during reading and writing. Reading increased the lateralization of the children with dyslexia, which had a negative relation to arithmetic; writing caused a decrease in lateralization, which was linked specifically to deficits in phonological decoding and visual word recognition. The results suggest that children with dyslexia suffer from a selective linguistic vulnerability to left-hemisphere interference from the idiosyncratic attentional and processing demands of particular school tasks. Dyslexia is a much more dynamic and environmentally sensitive disorder than previously thought.     

Cognitive and Linguistic Precursors to Early Literacy Achievement in Children With Specific Language Impairment

This study investigated the role of cognitive and language skills as predictors of early literacy skills in children with Specific Language Impairment. A range of cognitive and linguistic skills were assessed in a sample of 137 eight-year-old children with SLI at the beginning of the school year, and 6 months later on word decoding and reading comprehension. The cognitive and linguistic measures revealed four factors that were called language, speech, short-term memory, and phonological awareness. Structural equation modeling showed word decoding to be predicted by speech, short-term memory, and phonological awareness, whereas reading comprehension was predicted by word decoding skills and short-term memory. It can be concluded that in children with SLI variations in early word decoding are mostly determined by speech abilities and short-term memory, and to a lesser extent by phonological awareness. Moreover, reading comprehension turns out to be highly dependent on word decoding and short-term memory.     

Sound-symbol learning in children with dyslexia

This study evaluated the effect of sound-symbol association training on visual and phonological memory in children with a history of dyslexia. Pretests of phonological and visual memory, a sound-symbol training procedure, and phonological and visual memory posttests were administered to children with dyslexia, to children whose dyslexia had been compensated through remedial training, and to age- and reading level-matched comparison groups. Deficits in visual and phonological memory and memory for sound-symbol associations were demonstrated in the dyslexia group. For children with dyslexia and children whose dyslexia had been remediated, the sound-symbol training scores were significantly associated with word and pseudoword reading scores and were significantly lower than those of the comparison groups. Children with dyslexia and children whose dyslexia had been compensated showed significantly less facilitation of phonological memory following the training than did typical readers. Skilled readers showed some reduction in accuracy of visual memory following the training, which may be the result of interference of verbalization with a predominantly visual task. A parallel decrease was not observed in the children with dyslexia, possibly because these children did not use the verbal cues. Children with dyslexia and children whose dyslexia had been compensated seemed to have difficulty encoding the novel sounds in memory. As a result, they derived less phonological memory advantage and less visual memory interference from the training than did typical readers. Children in the compensated dyslexia group scored lower on sound-symbol training than their age peers. In other respects, the scores of these children were equivalent to those of the typically reading comparison groups. Children in the compensated dyslexia group exhibited higher phonological rehearsal, iconic memory, and associative memory scores than children in the dyslexia group. Implications for the remediation of dyslexia are discussed.     

Reading comprehension skills of young adults with childhood diagnoses of dyslexia

This study explores the contribution of cognitive processes to comprehension skills in adults who suffered from childhood developmental dyslexia (CD). The performance of adults with CD (ages 17 to 23), chronological age-matched (CA) adults, and reading level-matched (RL) children was compared on measures of phonological processing, naming speed, working memory (WM), general knowledge, vocabulary, and comprehension. The results showed that adults with CD scored lower on measures of phonological processing, naming speed, WM, general knowledge, and vocabulary when compared to CA readers but were comparable to RL children on the majority of process measures. Phonological processing, naming speed, vocabulary, general knowledge, and listening comprehension contributed independent variance to reading comprehension accuracy, whereas WM, intelligence, phonological processing, and listening comprehension contributed independent variance to comprehension fluency. Adults with CD scored lower than CA adults and higher than RL children on measures of lexical processing, WM, and listening comprehension when word recognition and intelligence were partialed from the analysis. In summary, constraints in phonological processing and naming speed mediate only some of the influence of high-order processes on reading comprehension. Furthermore, adults with CD experience difficulties in WM, listening comprehension, and vocabulary independently of their word recognition problems and intellectual ability.     

Cognitive constraints and the early learning goals in writing

This study examined the relative importance of a number of cognitive factors (i.e. working memory, vocabulary knowledge, general cognitive ability and reading skills) in accounting for differences in the rate of progress made by children in the development of emergent writing skills. Sixty-seven children were assessed on tasks measuring the visuospatial, phonological and central executive components of working memory. The children's written texts were analysed according to the assessment scale for writing from the Early Years Foundation Stage Profile. The results indicate that reading performance and visuospatial memory skills are crucial to determining whether or not children aged 4–5 years are able to meet the UK government's prescribed educational standards for writing. The importance of visual skills in the acquisition of orthographic knowledge and writing conventions gained through reading is discussed in relation to current instructional strategies within schools.     

Specific impairment in developmental reading disabilities: a working memory approach

Children with developmental reading disabilities (RD) frequently display impaired working memory functioning. However, research has been divergent regarding the characteristics of the deficit. Our investigation addressed this controversy by assessing Baddeley's working memory model as a whole rather than focusing on particular aspects of it, as has been done by much of the research to date. Participants included 20 children with RD and 20 typical readers between the ages of 9 and 13. The phonological loop, visual-spatial sketchpad, and central executive were assessed according to Baddeley's model. The results demonstrated that children with RD have an impaired phonological loop but intact visual-spatial sketchpad and central executive functioning as compared to controls. In terms of the phonological loop, the deficit appears to be specific to the phonological store. Furthermore, our research supports a relationship between phonological processing and phonological loop functioning.     

Toward a research-based assessment of dyslexia: using cognitive measures to identify reading disabilities

One hundred five participants from a random sample of elementary and middle school children completed measures of reading achievement and cognitive abilities presumed, based on a synthesis of current dyslexia research, to underlie reading. Factor analyses of these cognitive variables (including auditory processing, phonological awareness, short-term auditory memory, visual memory, rapid automatized naming, and visual processing speed) produced three empirically and theoretically derived factors (auditory processing, visual processing/speed, and memory), each of which contributed to the prediction of reading and spelling skills. Factor scores from the three factors combined predicted 85% of the variance associated with letter/sight word naming, 70% of the variance associated with reading comprehension, 73% for spelling, and 61% for phonetic decoding. The auditory processing factor was the strongest predictor, accounting for 27% to 43% of the variance across the different achievement areas. The results provide practitioner and researcher with theoretical and empirical support for the inclusion of measures of the three factors, in addition to specific measures of reading achievement, in a standardized assessment of dyslexia. Guidelines for a thorough, research-based assessment are provided.     

A technique for group screening of dyslexia among adults

This paper reports on the development of a battery of phonological processing tasks to screen adults with dyslexia. The battery consisted of tasks tapping reversed spoonerism, phonological choice, working memory, and vocabulary with confusable alternatives. A self-report questionnaire consisting of two scales, one examining symptoms of dyslexia and the other reading interests, was also constructed. All these tasks showed high discrimination between a group of adults with dyslexia and a control group, all recruited from adult education centers. The tasks also correlated highly with word recognition. The results of the study show that it is possible to develop a sensitive battery of “nonvocalized” tasks to screen adults with dyslexia on a group basis and that self-reports add to the screening. The group administration is both time-saving and cost-effective.     

The cognitive profile of adult dyslexics and its relation to their reading abilities

The question of which cognitive impairments are primarily associated with dyslexia has been a source of continuous debate. This study examined the cognitive profile of Hebrew-speaking compensated adult dyslexics and investigated whether their cognitive abilities accounted for a unique variance in their reading performance. Sixty-nine young adults with and without dyslexia were administered a battery of tests measuring their reading skills and a number of cognitive abilities. The dyslexics were found to exhibit a generally poor cognitive profile, including their attention, visual working memory, naming, visual perception and speed of processing abilities, with the exception of high executive functions skills. Furthermore, naming speed, visual working memory and attention were significantly associated with decoding and fluency measures and predicted group difference after controlling for phonological skills. The findings point to the contribution of cognitive factors to decoding rate and possibly to the ability of utilizing rapid orthographic processes, thus effecting dyslexics’ reading performance.     

The unique role of lexical accessibility in predicting kindergarten emergent literacy

The goal of this longitudinal study was to examine how lexical quality predicts the emergence of literacy abilities in 169 Dutch kindergarten children before formal reading instruction has started. At the beginning of the school year, a battery of precursor measures associated with lexical quality was related to the emergence of letter knowledge and word decoding. Confirmatory factor analysis evidenced five domains related to lexical quality, i.e., vocabulary, phonological coding, phonological awareness, lexical retrieval and phonological working memory. Structural equation modeling showed that the development of letter knowledge during the year could be predicted from children’s phonological awareness and lexical retrieval, and the emergence of word decoding from their phonological awareness and letter knowledge. It is concluded that it is primarily the accessibility of phonological representations in the mental lexicon that predicts the emergence of literacy in kindergarten.     

Developmental links of very early phonological and language skills to second grade reading outcomes: strong to accuracy but only minor to fluency

The authors examined second grade reading accuracy and fluency and their associations via letter knowledge to phonological and language predictors assessed at 3.5, 4.5, and 5.5 years in children in the Jyv?skyl? Longitudinal Study of Dyslexia. Structural equation modeling showed that a developmentally highly stable factor (early phonological and language processing [EPLP]) behind key dyslexia predictors (i.e., phonological awareness, short-term memory, rapid naming, vocabulary, and pseudoword repetition) could already be identified at 3.5 years. EPLP was significantly associated with reading and spelling accuracy and by age with letter knowledge. However, EPLP had only a minor link with reading fluency, which was additionally explained by early letter knowledge. The results show that reading accuracy is well predicted by early phonological and language skills. Variation in fluent reading skills is not well explained by early skills, suggesting factors other than phonological core skills. Future research is suggested to explore the factors behind the development of fast and accurate decoding skills.     

Do different components of working memory underlie different subgroups of reading disabilities?

The purpose of this study was to determine the components of working memory (WM) that underlie less skilled readers' comprehension and word recognition difficulties. Performance of 3 less skilled reading subgroups---children with reading disabilities (RD) in both word recognition and comprehension; children with comprehension deficits only; and children with low verbal IQ, word recognition, and comprehension (poor readers)--was compared to that of skilled readers on WM, short-term memory (STM), processing speed, executive, and phonological processing measures. Ability group comparisons showed that (a) skilled readers outperformed all less skilled readers on measures of WM, updating, and processing speed; (b) children with comprehension deficits only outperformed children with RD on measures of WM, STM, phonological processing, and processing speed; and (c) children with RD outperformed poor readers on WM and phonological processing measures. A hierarchical regression analysis showed that (a) subgroup differences on WM tasks among less skilled readers were moderated by a storage system not specific to phonological skills, and (b) STM and updating contributed significant variance to WM beyond what was contributed by reading group classification. The latter finding suggested that some differences in storage and executive processing emerged between skilled and less skilled readers that were not specific to reading.     

An evaluation of the discrepancy definition of dyslexia.

The purpose of this study was to determine whether children with dyslexia, that is, children whose reading levels were significantly lower than would be predicted by their IQ scores, constituted a distinctive group when compared with poor readers, that is, children whose reading scores were consistent with their IQ scores. The performance of children with dyslexia, poor readers, and normally achieving readers was compared on a variety of reading, spelling, phonological processing, language, and memory tasks. Although the children with dyslexia had significantly higher IQ scores than the poor readers, these two groups did not differ in their performance on reading, spelling, phonological processing, or most of the language and memory tasks. In all cases, the performance of both reading disabled groups was significantly below that of nondisabled readers. The findings were similar whether absolute difference or regression scores were used. Reading disabled children, whether or not their reading is significantly below the level predicted by their IQ scores, experience significant problems in phonological processing, short-term and working memory, and syntactic awareness. On the basis of these data, there does not seem to be a need to differentiate between individuals with dyslexia and poor readers. Both of these groups are reading disabled and have deficits in phonological processing, verbal memory, and syntactic awareness.     

Improving children's working memory and classroom performance

Previous research has demonstrated close relationships between working memory and children's scholastic attainment. The aim of the present study was to explore a method of improving working memory, using memory strategy training. Two hundred and fifty‐four children aged five to eight years were tested on measures of the phonological loop, visuo‐spatial sketchpad and central executive components of the multiple component model of working memory. Subgroups of children also completed tasks of following instructions and mental arithmetic in the classroom, and standardised tests of reading, arithmetic and mathematics. Half of the children then used Memory Booster, a computer game that teaches memory strategies, over a period of six to eight weeks. All the children were then retested on the memory and ability measures. The standardised tests were also administered five months later. The results revealed that working memory strategy training resulted in significant improvements in tasks assessing the phonological loop and central executive components of working memory, and tasks assessing following instructions and mental arithmetic in the classroom. However, no improvements were observed on standardised tests of reading, arithmetic or mathematics, either immediately following training or five months later. The results are discussed in terms of implications for educational practice.     

Influence of Verbal Working Memory Depends on Vocabulary: Oral Reading Fluency in Adolescents With Dyslexia

Most research on dyslexia to date has focused on early childhood, while comparatively little is known about the nature of dyslexia in adolescence. The current study had two objectives. The first was to investigate the relative contributions of several cognitive and linguistic factors to connected‐text oral reading fluency in a sample of adolescents with dyslexia (n = 77). The second was to test the hypothesis that the effect of verbal working memory on connected‐text oral reading fluency is moderated by word‐level skills and/or vocabulary knowledge. The results suggest that many deficits associated with childhood dyslexia remain prominent in adolescence, but the nature of the relationships between key cognitive and linguistic predictors (i.e., word‐level reading, vocabulary, verbal working memory) and reading fluency appear to be different in adolescence. For example, while word‐level skills remain a significant predictor, the strength of the effect is relatively weak. In contrast, the data support an increased role for vocabulary and verbal working memory, including an interaction between these factors. The presence of an interaction can be interpreted as evidence that the influence of verbal working memory on connected‐text oral reading fluency in adolescents with dyslexia depends on individual differences in vocabulary knowledge. These results offer support for the changing nature of dyslexia across development, and suggest that researchers should study dyslexia in adolescents on its own terms, rather than treating it as an extension of reading problems in early childhood.