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

Acquisition of Reading and Intellectual Development Disorder

We propose a review of the literature of the studies investigating reading acquisition in intellectual deficiency (ID), with particular focus on the explanatory factors for reading difficulties. Indeed, we explore the role of intellectual efficiency, perceptual abilities, oral language development, phonological processing and memory. The study of reading acquisition in ID is a challenge because of a high degree of heterogeneity in the results which, together with other variables influencing learning and development. This review has allowed us to understand that there are multiple reasons why individuals with ID have difficulty learning to read. More specifically, there is a link between reading skills and certain cognitive skills, such as perception, oral language, phonological processing and working memory.

Decoding: It's Not All About the Letters

Purpose

Reading requires the ability to decode and comprehend. Impairments in working memory (WM) are often implicated in students who are poor decoders. It is unclear whether this is a domain-specific issue or a task-specific issue. Therefore, this study examined how auditory-verbal (AV) WM, visual-spatial (VS) WM, and cognitive load affected the decoding skills of students identified as poor readers.

Method

Twenty-five 2nd-grade and 23 fifth-grade students completed 3 different measures requiring various levels of cognitive demand for each domain of WM, and their decoding skills were assessed with word identification and word attack measures.

Results

AV WM measures with moderate and high cognitive demands were correlated with 2nd-grade students' abilities to decode words. AV WM measures also predicted their performance on decoding tasks. For 5th-grade students, the AV WM measure with simple cognitive load was correlated with ability to decode words. The VS WM measures were not correlated with word identification or word attack at either level.

Conclusions

This study has implications for training instruction in reading. Because the AV WM measures and not the VS WM measures predicted decoding performance in second graders, a greater emphasis on language-rich reading programs could be beneficial in scaffolding early academic achievement and reading performance.

Working memory span in Persian-speaking children with speech sound disorders and normal speech development

OBJECTIVES

The aim of this study was to compare working memory span in Persian-speaking preschool children with speech sound disorder (SSD) and their typically speaking peers. Additionally, the study aimed to examine Non-Word Repetition (NWR), Forward Digit Span (FDS) and Backward Digit Span (BDS) in four groups of children with varying severity levels of SSD.

METHODS

The participants in this study comprised 35 children with SSD and 35 typically developing (TD) children -matched for age and sex-as a control group. The participants were between the age range of 48 and 72 months. Two components of working memory including phonological loop and central executive were compared between two groups. We used two tasks (NWR and FDS) to assess phonological loop component, and one task (BDS) to assess central executive component. Percentage of correct consonants (PCC) was used to calculate the severity of SSD.

RESULTS

Significant differences were observed between the two groups in all tasks that assess working memory (p < 0.001). In addition, the comparison of the phonological loop of working memory between the various severity groups indicated significant differences between different severities of both NWR and FDS tasks among the SSD children (p < 0.001). Nevertheless, comparison of the central executive between various severity groups, which was assessed with the BDS task, did not show any significant differences (p > 0.05). The result showed that PCC scores in TD children were associated with NWR (p < 0.001), FDS (p = 0.001), and BDS (p < 0.001). Furthermore, PCC scores in SSD children were associated with NWR and FDS (p < 0.001), but not with BDS (p > 0.05).

CONCLUSION

The working memory skills were weaker in SSD children, in comparison to TD children. In addition, children with varying levels of severity of SSD differed in terms of NWR and FSD, but not BDS.

Unpacking Direct and Indirect Relationships of Short-Term Memory to Word Reading: Evidence From Korean-Speaking Children

We examined the relations of short-term memory (STM), metalinguistic awareness (phonological, morphological, and orthographic awareness), and rapid automatized naming (RAN) to word reading in Korean, a language with a relatively transparent orthography. STM, metalinguistic awareness, and RAN have been shown to be important to word reading, but the nature of the relations of STM, metalinguistic awareness, and RAN to word reading has rarely been investigated. Two alternative models were fitted. In the indirect relation model, STM was hypothesized to be indirectly related to word reading via metalinguistic awareness and RAN. In the direct and indirect relations model, STM was hypothesized to be directly and indirectly related to word reading. Results from 207 beginning readers in South Korea showed that STM was directly related to word reading as well as indirectly via metalinguistic awareness and RAN. Although the direct effect of STM was relatively small (.16), the total effect incorporating the indirect effect was substantial (.42). These results suggest that STM is an important, foundational cognitive capacity that underpins metalinguistic awareness and RAN as well as word reading, and further indicate the importance of considering both direct and indirect effects of language and cognitive skills on word reading.

Working memory studies among individuals with intellectual disability: An integrative research review

BACKGROUND

Integrative research review infers generalizations about a substantive subject, summarizes the accumulated knowledge that research has left unresolved and generates a new framework on these issues. Due to methodological issues emerging from working memory (WM) studies in the population with non-specific intellectual disability (NSID) (N=64) between 1990-2014, it is difficult to conclude on WM performance in this population.

AIM

This integrative research review aimed to resolve literature conflicts on WM performance among individuals with NSID and to identify the conditions/moderators that govern their WM performance compared to controls with Typical development.

METHOD/PROCEDURE

We used the six stages of integrative research review: problem formulation, data collection, evaluation, data analysis, results, interpretation and discussion.

OUTCOMES AND RESULTS

The findings indicate two types of moderators that determine WM performance in the population with NSID: Participants' moderators (criteria for matching the ID and TD groups, CA and MA), and task moderators [the three WM components of Baddeley and Hitch's (1974) model and task load]. Only an interaction between the two moderators determines WM performance in this population. The findings indicate a hierarchy (from more to less preserved) in WM performance of individuals with NSID: The visuospatial tasks, then some of the executive functions tasks, and the phonological loop tasks being less preserved. Furthermore, at a low level of control, the performance of participants with NSID was preserved beyond the modality and vice versa.

CONCLUSIONS AND IMPLICATIONS

Modality and MA/intelligence determine WM performance of individuals with ID. Educators should prepare intervention programs take the impact of the two moderators into account.

Untangling the Contribution of the Subcomponents of Working Memory to Mathematical Proficiency as Measured by the National Tests: A Study among Swedish Third Graders

The aim with the present study was to examine the relationship between the subcomponents in working memory (WM) and mathematical performance, as measured by the National tests in a sample of 597 Swedish third-grade pupils. In line with compelling evidence of other studies, individual differences in WM capacity significantly predicted mathematical performance. Dividing the sample into four groups, based on their mathematical performance, revealed that mathematical ability can be conceptualized in terms of different WM profiles. Pupils categorized as High-math performers particularly differed from the other three groups in having a significant higher phonological ability. In contrast, pupils categorized as Low-math performers were particularly characterized by having a significant lower visuo-spatial ability. Findings suggest that it is important for educators to recognize and acknowledge individual differences in WM to support mathematical achievement at an individual level.

The effectiveness of working memory training with individuals with intellectual disabilities - a meta-analytic review

Working memory (WM) training has been increasingly popular in the last years. Previous studies have shown that individuals with intellectual disabilities (ID) have low WM capacity and therefore would benefit by this type of intervention. The aim of this study was to investigate the effect of WM and cognitive training for individuals with ID. The effects reported in previous studies have varied and therefore a meta-analysis of articles in the major databases was conducted. Inclusion criteria included to have a pretest-posttest design with a training group and a control group and to have measures of WM or short-term memory. Ten studies with 28 comparisons were included. The results reveal a significant, but small, overall pretest-posttest effect size (ES) for WM training for individuals with ID compared to controls. A mixed WM approach, including both verbal and visuo-spatial components working mainly on strategies, was the only significant training type with a medium ES. The most commonly reported training type, visuo-spatial WM training, was performed in 60 percent of the included comparisons and had a non-significant ES close to zero. We conclude that even if there is an overall effect of WM training, a mixed WM approach appears to cause this effect. Given the few studies included and the different characteristics of the included studies, interpretations should be done with caution. However, different types of interventions appear to have different effects. Even if the results were promising, more studies are needed to better understand how to design an effective WM intervention for this group and to understand if, and how, these short-term effects remain over time and transfer to everyday activities.

Working memory development in children with mild to borderline intellectual disabilities

BACKGROUND

The purpose of the current cross-sectional study was to examine the developmental progression in working memory (WM) between the ages of 9 and 16 years in a large sample of children with mild to borderline intellectual disabilities (MBID). Baddeley's influential WM model was used as a theoretical framework. Furthermore, the relations between WM on the one hand, and scholastic skills (arithmetic and reading) on the other were examined.

METHOD

One hundred and ninety-seven children with MBID between 9 and 16 years old participated in this study. All children completed several tests measuring short-term memory, WM, inhibition, arithmetic and single word reading.

RESULTS

WM, visuospatial short-term memory and inhibition continued to develop until around age 15 years. However verbal short-term memory showed no further developmental increases after the age of 10 years. Verbal short-term memory was associated with single word reading, whereas inhibition was associated with arithmetic.

DISCUSSION

The finding that verbal short-term memory ceases to develop beyond the age of 10 years in children with MBID contrasts with results of studies involving typically developing children, where verbal short-term memory develops until around age 15 years. This relative early developmental plateau might explain why verbal short-term memory is consistently considered weak in children with MBID.

Phonological short-term memory impairment and the word length effect in children with intellectual disabilities

There is mounting evidence that children and adolescents with intellectual disabilities (ID) of nonspecific aetiology perform poorer on phonological short-term memory tasks than children matched for mental age indicating a structural deficit in a process contributing to short-term recall of verbal material. One explanation is that children with ID of nonspecific aetiology do not activate subvocal rehearsal to refresh degrading memory traces. However, existing research concerning this explanation is inconclusive since studies focussing on the word length effect (WLE) as indicator of rehearsal have revealed inconsistent results for samples with ID and because in several existing studies, it is unclear whether the WLE was caused by rehearsal or merely appeared during output of the responses. We assumed that in children with ID only output delays produce a small WLE while in typically developing 6- to 8-year-olds rehearsal and output contribute to the WLE. From this assumption we derived several predictions that were tested in an experiment including 34 children with mild or borderline ID and 34 typically developing children matched for mental age (MA). As predicted, results revealed a small but significant WLE for children with ID that was significantly smaller than the WLE in the control group. Additionally, for children with ID, a WLE was not found for the first word of each trial but the effect emerged only in later serial positions. The findings corroborate the notion that in children with ID subvocal rehearsal does not develop in line with their mental age and provide a potential explanation for the inconsistent results on the WLE in children with ID.

Are poor Chinese text comprehenders also poor in written composition?

We studied the performance in three genres of Chinese written composition (narration, exposition, and argumentation) of 158 grade 4, 5, and 6 poor Chinese text comprehenders compared with 156 good Chinese text comprehenders. We examined text comprehension and written composition relationship. Verbal working memory (verbal span working memory and operation span working memory) and different levels of linguistic tasks-morphological sensitivity (morphological compounding and morphological chain), sentence processing (syntax construction and syntax integrity), and text comprehension (narrative and expository texts)-were used to predict separately narrative, expository, and argumentation written compositions in these students. Grade for grade, the good text comprehenders outperformed the poor text comprehenders in all tasks, except for morphological chain. Hierarchical multiple regression analyses showed differential contribution of the tasks to different genres of writing. In particular, text comprehension made unique contribution to argumentation writing in the poor text comprehenders. Future studies should ask students to read and write parallel passages in the same genre for better comparison and incorporate both instructional and motivational variables.

Strengths and weaknesses in executive functioning in children with intellectual disability

Children with intellectual disability (ID) were given a comprehensive range of executive functioning measures, which systematically varied in terms of verbal and non-verbal demands. Their performance was compared to the performance of groups matched on mental age (MA) and chronological age (CA), respectively. Twenty-two children were included in each group. Children with ID performed on par with the MA group on switching, verbal executive-loaded working memory and most fluency tasks, but below the MA group on inhibition, planning, and non-verbal executive-loaded working memory. Children with ID performed below CA comparisons on all the executive tasks. We suggest that children with ID have a specific profile of executive functioning, with MA appropriate abilities to generate new exemplars (fluency) and to switch attention between tasks, but difficulties with respect to inhibiting pre-potent responses, planning, and non-verbal executive-loaded working memory The development of different types of executive functioning skills may, to different degrees, be related to mental age and experience.

Relationships Between Working Memory and Academic Skills: Are There Differences Between Children With Intellectual Disabilities and Typically Developing Children?

In typically developing children, working memory is linked to academic skills. However, little is known about the role working memory plays for learning in children with intellectual disabilities (ID). Therefore, the aims of this study were to examine whether different working memory functions are related to reading, spelling, and calculating in children with ID of nonspecific etiology and whether these relationships are different from the ones found in typically developing children. Forty-seven children with mild-to-borderline ID and 47 children matched for mental age were tested. Although in typically developing children, only phonological short-term memory tasks were predictive for literacy, for children with ID, visuospatial working memory tasks also accounted for variance. In typically developing children, calculation skills were predicted by phonological working memory tasks, whereas visuospatial working memory resources were crucial for children with ID. Several possible explanations are discussed for discrepancies in prediction patterns.

Ein modalitätsspezifisches Wortgedächtnis ist ausreichend: Wortgedächtnismodalität bei Leseanfängern und Neuronalen Netzen 1Dieser Beitrag wurde unter der geschäftsführenden Herausgeberschaft von Jens Möller angenommen

Zusammenfassung. Wortstruktureffekte besagen, dass bekannte Buchstabenfolgen von vertrauten Worten einfacher zu erinnern und leichter zu lesen sind, als weniger bekannte oder neue Buchstabenfolgen von seltener auftretenden Worten. Es ist daher einleuchtend, dass eine quantitative Zunahme an neuer Wortstruktur den Leseschwierigkeitsgrad vorhersagt. Z. B. sind Zahlworte leichter zu lesen als Reimworte mit neuem Wortanfang, und Reimworte sind wiederum leichter zu lesen als Nicht-Worte mit neuer Buchstabenfolge. Deutsche Leseanfänger zeigten jedoch nicht diesen häufig zu beobachtenden Wortstruktureffekt beim Lesen ( Lange-Küttner, 2005 ). Hängt dies möglicherweise damit zusammen, dass sie eine Prävalenz des auditorischen Gedächtnisses beim Lesen haben ( Gathercole & Baddeley, 1993 )? Es wurde daher bei englischsprachigen und deutschen Kindern der Zusammenhang des Lesens mit dem Wortstruktureffekt im auditiven vs. visuellen Wortgedächtnis analysiert. Während der Wortstruktureffekt im visuellen Gedächtnis bei allen Kindern vorhanden war, zeigte er sich im auditiven Gedächtnis nur bei den früh eingeschulten britischen Kindern. Lesen war mit dem visuellen Wortgedächtnis bei den englischsprachigen Kindern korreliert, jedoch mit dem auditiven Wortgedächtnis bei den deutschen Kindern. Auch neuronale Netze brauchten nur ein Arbeitsgedächtnis. Mögliche Auswirkungen der Selektivität des Arbeitsgedächtnisses auf das Lesen, sowie Folgen von unimodaler und bimodaler Wortrepräsentation bei Kindern und in neuronalen Netzen werden erörtert.

Do tasks make a difference? Accounting for heterogeneity of performance of children with reading difficulties on tasks of executive function: findings from a meta-analysis

Research studies have implicated executive functions in reading difficulties (RD). But while some studies have found children with RD to be impaired on tasks of executive function other studies report unimpaired performance. A meta-analysis was carried out to determine whether these discrepant findings can be accounted for by differences in the tasks of executive function that are utilized. A total of 48 studies comparing the performance on tasks of executive function of children with RD with their typically developing peers were included in the meta-analysis, yielding 180 effect sizes. An overall effect size of 0.57 (SE .03) was obtained, indicating that children with RD have impairments on tasks of executive function. However, effect sizes varied considerably suggesting that the impairment is not uniform. Moderator analysis revealed that task modality and IQ-achievement discrepancy definitions of RD influenced the magnitude of effect; however, the age and gender of participants and the nature of the RD did not have an influence. While the children's RD were associated with executive function impairments, variation in effect size is a product of the assessment task employed, underlying task demands, and definitional criteria.

Working memory and educational achievement in children with intellectual disabilities

BACKGROUND

There is little previous research examining whether measures of working memory are related to educational achievement in children with intellectual disabilities (ID).

METHODS

A battery of working memory and achievement measures was administered to 11- to 12-year-old children with ID; younger typically developing children of comparable mental age were also assessed.

RESULTS

The working memory measures that assessed phonological short-term memory (PSTM) accounted for the most variance in reading and spelling in children with ID, whereas the working memory measures that assessed central executive-loaded working memory (CELWM) accounted for the most variance in number skills. These relationships were broadly similar among typically developing children.

CONCLUSIONS

Compensatory strategies for weak PSTM may help to improve reading and spelling skills in children with ID, whereas reducing CELWM loads may be more helpful in aiding their number skills.

Memory profiles in children with mild intellectual disabilities: strengths and weaknesses

Strengths and weaknesses in short-term memory (STM) and working memory (WM) were identified in children with mild intellectual disabilities (MID) by comparing their performance to typically developing children matched on chronological age (CA children) and to younger typically developing children with similar mental capacities (MA children). Children with MID performed less well on all measures compared to the CA children. Relative to the MA children, especially verbal WM was weak. Subsequent analyses yielded distinct MID subgroups each with specific memory strengths and weaknesses. These findings hold implications for the demands imposed on children with MID in education and daily life.

Working memory, short-term memory, and reading disabilities: a selective meta-analysis of the literature

The purpose of the present study was to synthesize research that compares children with and without reading disabilities (RD) on measures of short-term memory (STM) and working memory (WM). Across a broad age, reading, and IQ range, 578 effect sizes (ESs) were computed, yielding a mean ES across studies of -.89 (SD = 1.03). A total of 257 ESs were in the moderate range for STM measures (M = -.61, 95% confidence range of -.65 to -.58), and 320 ESs were in the moderate range for WM measures (M = -.67, 95% confidence range of -.68 to -.64). The results indicated that children with RD were distinctively disadvantaged compared with average readers on (a) STM measures requiring the recall of phonemes and digit sequences and (b) WM measures requiring the simultaneous processing and storage of digits within sentence sequences and final words from unrelated sentences. No significant moderating effects emerged for age, IQ, or reading level on memory ESs. The findings indicated that domain-specific STM and WM differences between ability groups persisted across age, suggesting that a verbal deficit model that fails to efficiently draw resources from both a phonological and executive system underlies RD.

Component skills of text comprehension in less competent Chinese comprehenders

The present study examined the role of verbal working memory (memory span and tongue-twister), two-character Chinese pseudoword reading (two tasks), rapid automatized naming (RAN) (letters and numbers), and phonological segmentation (deletion of rimes and onsets) in inferential text comprehension in Chinese in 31 less competent comprehenders compared with 37 reading comprehension control students and 23 chronological age controls. It was hypothesized that the target students would perform poorly on these cognitive and linguistic tasks as compared with their controls. Furthermore, verbal working memory and pseudoword reading would explain a considerable amount of individual variation in Chinese text comprehension. RAN would have a nonsignificant role in text comprehension. Structural equation analyses and hierarchical multiple regression analyses generally upheld these hypotheses. Our findings support current literature of the role of verbal working memory in reading comprehension found in English. The results, however, suggest differential role of the constructs and the tasks in reading comprehension and provide some answers for comprehension impairment in Chinese students.

Individual differences in working memory

Working memory can be defined as the ability to hold in mind information in the face of potentially interfering distraction in order to guide behavior. The experimental manipulation of working memory tasks has shed considerable light on the probable structure of the human working memory system, and, to a lesser extent, the specific processes captured by working memory paradigms. However, individual differences research has also had a crucial role to play in the development of theories of working memory. In particular, correlational approaches have been particularly informative in three areas of working memory research, each of which is reviewed here. These are, first, the importance of working memory measures as correlates of high-level cognitive skills such as reading, mathematics, reasoning, and fluid intelligence; second, the extent to which human working memory relies on domain-general or domain-specific component subsystems, and third, the precise reasons why working memory measures do relate to other important indices of human cognitive functioning. The findings from each of these areas suggest that working memory depends on a combination of domain-specific representational systems and domain-general processing and control systems, and that working memory measures capture individuals' ability to combine maintenance and processing demands in a manner that limits information loss from forgetting or distraction.