Mathematical problem solving and working memory in children with learning disabilities: both executive and phonological processes are important.

The purpose of this investigation was to explore the relationship between working memory (WM) and mathematical problem solving in children with learning disabilities (LD). Children with LD (age 11.5 years) were compared to chronologically age-matched (CA-M) and younger comprehension/computation achievement-matched children (age 8.9 years) on measures of verbal and visual-spatial WM, phonological processing, components of problem solving, and word-problem solving accuracy. The results showed that (1) children with LD were inferior on measures of word solution accuracy, components of problem solving, phonological processing, domain-general WM, and verbal WM when compared to children who were CA-M, (2) children with LD were comparable to younger children on all processing measures, except measures of domain-general WM, visual-spatial WM, phonemic deletion, and identifying problem goals, (3) measures of verbal and visual-spatial WM contributed significant variance to solution accuracy independent of phonological processing, and (4) the influence of WM on solution accuracy was mediated by long-term memory (LTM) processes related to the knowledge of algorithms. The results support the notion that information activated from LTM, rather than phonological processing, mediates the relationship between executive processing and solution accuracy in children with LD.

Treatment outcomes for students with learning disabilities: how important are internal and external validity?

This study analyzed the magnitude of experimental intervention outcomes as a function of violations in internal and external validity for studies that included students with learning disabilities. The results indicated that treatment outcomes were significantly affected by the following violations: teacher effects, establishing criterion levels of instructional performance, reliance on experimental measures, using different measures between pretest and posttest, using a sample heterogenous in age, and using incorrect units of analysis. Furthermore, the underreporting of information related to ethnicity, locale of the study, psychometric data, and teacher applications positively inflated the magnitude of treatment outcomes. A weighted hierarchical regression analysis revealed that composite scores of the aforementioned high-risk variables accounted for 16% of the total variance in effect size. The implications for interpreting intervention research to practice are discussed.

Are mathematics disabilities due to a domain-general or a domain-specific working memory deficit?

The relationship between verbal and visual-spatial working memory and mathematical computation skill was examined in children and adults with and without disabilities in mathematics. A hierarchical regression analysis showed that, when partialing for the influence of reading ability, age, and gender, mathematical computation was better predicted by verbal than by visual-spatial working memory. Furthermore, the results showed that the relationship between mathematics ability and working memory were not significantly moderated by age but were stable across a broad age span. We concluded that, regardless of age, deficits in mathematics are mediated by both a domain-general and a domain-specific working memory system.

A subgroup analysis of working memory in children with reading disabilities: domain-general or domain-specific deficiency?

The purpose of this study was to investigate whether changes in working memory (WM) of children with reading disabilities (RD) were related to a domain-specific or a domain-general system. Based on Daneman and Carpenter's (1980) Sentence Listening Span task, children were subgrouped into a group of high executive processing (high listening span) children without RD, a group of low executive processing (low listening span) children with RD, and a group of children with and without RD matched on executive processing (moderate listening span). Subgroups were compared on phonological, visual-spatial, and semantic WM tasks across initial (no probes or cues), gain (cues that bring performance to an asymptotic level), and maintenance conditions (asymptotic conditions without cues). The results showed that (a) children without RD high in executive processing ability outperformed all other subgroups, (b) the RD subgroup low in executive processing performed poorly relative to all other subgroups across task and memory conditions, (c) children with and without RD matched on executive processing were comparable in WM span and changes in WM for all tasks, and (d) WM performance of children with RD was a strong linear function of the high executive processing group, suggesting that the nature or the specific componential makeup of the tasks are not the main contributors to WM performance. Taken together, the results suggest that a domain-general system may partially contribute to poor WM in children with RD, and that this system may operate independently of their reading deficits.

Does strategy knowledge influence working memory in children with mathematical disabilities?

This study investigated the relationship between working memory (WM), declarative strategy knowledge, and math achievement in children with and without mathematical disabilities (MD). Experiment 1 examined the relationship between strategy knowledge, verbal WM, and visual-spatial WM in children with MD as a function of initial, gain, and maintenance conditions. The results showed that after partialing the influence of reading, stable strategy choices rather than specific strategy knowledge was related to verbal and visual-spatial WM span in high demand (maintenance) conditions. Experiment 2 compared children with MD to a group of chronological age-matched children and a group of math ability-matched children on the same conditions as Experiment 1. Age-matched children's verbal and visual-spatial WM performance was superior to that of children with MD, whereas WM performance was statistically comparable between children with MD and younger children matched on math ability. The selection of expert strategies was related to high WM span scores in the initial conditions. After controlling for reading achievement in a regression analysis, verbal and visual-spatial WM, stable verbal strategy choices, and expert strategy choices related to visual-spatial processing all contributed independent variance to math achievement. Overall, these results suggest that WM and math achievement are related to strategy knowledge.

A case of Peters' anomaly in a springer spaniel.

An 8-week-old springer spaniel presented with a large central corneal opacity of the left globe, which was accompanied by cords of tissue spanning from the iris collarette to the posterior cornea. A posterior cortical cataract was noted in the right eye. At the owner's request the puppy was humanely destroyed, and a necropsy was performed. Upon sectioning the left globe in the vertical plane, a circle of pigmented strands of tissue was observed spanning the anterior chamber from the iris to the posterior aspect of the cornea. The right globe appeared normal when inspected grossly. Histologically, a membrane of pigmented tissue covered the posterior aspect of the broad central corneal leukoma of the left globe. This membrane and the cords traversing the anterior chamber were composed of vascular uveal tissue. Descemet's membrane and the corneal endothelium were reduced or absent in the zone of corneal opacity. Other than the changes associated with cataract, the right globe was histologically normal. The clinical and histological findings in the left globe were identical with those described for Peters>> anomaly in human beings.

Are working memory deficits in readers with learning disabilities hard to change?

This study investigated whether changes in the working memory (WM) performance of readers with learning disabilities (LD) is related to a general or domain-specific system. The study compared readers with LD, chronologically age-matched (CA-M), and reading level-matched (RL-M) children's WM performance for phonological, visual-spatial, and semantic information under initial (no probes or cues), gain (cues that bring performance to an asymptotic level), and maintenance (asymptotic conditions without cues) conditions. The main findings indicated that (a) CA-M children were superior in performance to readers with LD across initial, gain, and maintenance conditions, (b) readers with LD showed less change (as reflected in effect size scores, slopes for the quadratic curve) on both visual-spatial and verbal (phonological and semantic) WM tasks across gain and maintenance conditions than the CA-matched children, and (c) the performance of readers with LD was superior to the RL-M children's performance on initial conditions, but inferior on gain and maintenance conditions. Taken together, the results suggest that a general system moderated the changes in retrieval of phonological, visual-spatial, and semantic information in readers with LD.

A meta-analysis of single-subject-design intervention research for students with LD.

This article summarizes single-subject-design intervention studies that include students with learning disabilities. Effect sizes of 85 studies were analyzed across instructional domains (e.g., reading, mathematics); sample characteristics (e.g., age, intelligence); intervention parameters (e.g., number of instructional sessions, instructional components); and methodological procedures (e.g., internal validity, treatment integrity, sample representation). The major findings were as follows: (a) All domain areas except handwriting yielded effect sizes at or above Cohen's .80 threshold for a substantial finding; (b) instructional components related to drill-repetition-practice-review, segmentation, small interactive groups, and the implementation of cues to use strategies contributed significant variance (15%) to estimates of effect size; (c) strategy instruction (SI) models better predicted effect size estimates than direct instruction (DI) models when the results were qualified by the reported intellectual and reading levels of the participants; (d) high-IQ discrepancy groups yielded lower effect sizes compared to low-IQ discrepancy groups in the domain of reading, whereas the reverse effect occurred when treatment outcomes were not reading measures; and (e) the low-IQ discrepancy groups yielded higher effect sizes for a Combined DI and SI Model when compared to competing models. The results are supportive of the pervasive influence of cognitive strategy and direct instruction models across treatment domains and of the notion that variations in sample definition moderate treatment outcomes.

A comparison of two reading interventions for children with reading disabilities.

This study compared the effectiveness of two reading interventions in a public school setting. Forty-five second-grade children with reading disabilities were randomly assigned to a 6-week phonological awareness, word analogy, or math-training program. The two reading interventions differed from each other in (a) the unit of word analysis (phoneme versus onset-rime), (b) the approach to intervention (contextualized versus decontextualized), and (c) the primary domain of reading instruction (oral versus written language). Results indicate that children in both reading programs achieved significant gains in beginning reading skills, learning the specific skills taught in their respective programs, and applying what they had learned to uninstructed material on several transfer-of-learning measures, in comparison to children in the control group. For children in both reading intervention groups, the most significant mediator of growth in oral reading fluency was a child's initial level of word identification skill. Implications of these findings are that systematic, high quality reading intervention can occur in a small group, public school setting and that there are several different paths to the remediation of children with reading disabilities.

What develops in working memory? A life span perspective.

This study investigated whether working-memory (WM) span differences across age are attributable to specific or general processing functions. The study compared 9 age groups (6, 8, 10, 13, 16, 24, 35, 45, 57 years) on verbal and visuospatial WM performance under initial (no probes or cues), gain (cues that bring performance to an asymptotic level), and maintenance conditions (asymptotic conditions without cues). (a) Age-related performance differences in WM were found across all conditions and were not isolated to specific processes, (b) significant performance differences remained among age groups on gain and maintenance conditions, and (c) the gain (accessing new information) and maintenance conditions (maintenance of old information) for verbal and visuospatial WM tasks contributed independent variance to age-related performance. The results support a general capacity explanation of age-related differences. These differences in capacity reflect demands placed on both the accessing of new information and the maintenance of old information.

Reading comprehension and working memory in learning-disabled readers: Is the phonological loop more important than the executive system?

This investigation explores the contribution of two working memory systems (the articulatory loop and the central executive) to the performance differences between learning-disabled (LD) and skilled readers. Performances of LD, chronological age (CA) matched, and reading level-matched children were compared on measures of phonological processing accuracy and speed (articulatory system), long-term memory (LTM) accuracy and speed, and executive processing. The results indicated that (a) LD readers were inferior on measures of articulatory, LTM, and executive processing; (b) LD readers were superior to RL readers on measures of executive processing, but were comparable to RL readers on measures of the articulatory and LTM system; (c) executive processing differences remained significant between LD and CA-matched children when measures of reading comprehension, articulatory processes, and LTM processes were partialed from the analysis; and (d) executive processing contributed significant variance to reading comprehension when measures of the articulatory and LTM systems were entered into a hierarchical regression model. In summary, LD readers experience constraints in the articulatory and LTM system, but constraints mediate only some of the influence of executive processing on reading comprehension. Further, LD readers suffer executive processing problems nonspecific to their reading comprehension problems.

Reading research for students with LD: a meta-analysis of intervention outcomes.

The present article provides a meta-analysis of instructional research with samples of children and adolescents with learning disabilities in the domains of word recognition and reading comprehension. The results of the synthesis showed that a prototypical intervention study has an effect size (ES) of .59 for word recognition and .72 for reading comprehension. Four important findings emerged from the synthesis: (a) Effect sizes for measures of comprehension were higher when studies included derivatives of both cognitive and direct instruction, whereas effect sizes were higher for word recognition when studies included direct instruction; (b) effect sizes related to reading comprehension were more susceptible to methodological variation than studies of word recognition; (c) the magnitude of ES for word recognition studies was significantly related to samples defined by cutoff scores (IQ > 85 and reading < 25th percentile), whereas the magnitude of ES for reading comprehension studies was sensitive to discrepancies between IQ and reading when compared to competing definitional criteria; and (d) instructional components related to word segmentation did not enter significantly into a weighted least square hierarchical regression analysis for predicting ES estimates of word recognition beyond an instructional core model, whereas small-group interactive instruction and strategy cuing contributed significant variance beyond a core model to ES estimates of reading comprehension. Implications related to definition and instructional components that optimize the magnitude of outcomes are discussed.

The role of the anesthesia care coordinator in preadmission testing.

Surgery delays and cancellations are costly to hospitals and emotionally distressful to patients. At Sarasota (Fla) Memorial Hospital, staff members developed a critical pathway-the preanesthesia collaborative care track, called "the Track," to address problems associated with preparing patients for surgery. The track is designed to facilitate preoperative patient assessments and nursing interventions that achieve desirable patient outcomes and to enhance the delivery of quality health care to surgical patients. The RN anesthesia care coordinator of the Track assists in early patient-problem identification and ensures that appropriate clinical data are available for perioperative nurses, anesthesiologists, and surgeons to avoid last-minute delays and cancellations of scheduled surgical procedures.

Individual differences in children's working memory and writing skill.

The purpose of this research is to address (a) whether individual differences in working memory (WM) and writing are related to a general or process-specific system, (b) whether WM tasks operate independently of phonological short-term memory (STM) on measures of writing and reading, and (c) whether working memory predicts variance in writing beyond that predicted by reading alone. The present study correlated several WM and phonological STM measures with writing and reading measures. The study showed among the memory measures that a four-factor model reflecting phonological STM, verbal WM span, executive processing, and visual-spatial WM span best fit the multivariate data set. Working memory was correlated significantly with a number of writing measures, particularly those related to text generation. WM measures contributed unique variance to writing that was independent of reading skill, and STM measures best predicted transcription processes and reading recognition, whereas WM measures best predicted text generation and reading comprehension. Both verbal and visual-spatial working memory measures predicted reading comprehension, whereas only WM measures that reflect executive processing significantly predicted writing. In general, the results suggest that individual differences in children's writing reflect a specific capacity system, whereas reading comprehension draws upon a multiple capacity system.

Learning disabled and average readers' working memory and comprehension: does metacognition play a role?

The present study investigates (a) whether learning disabled readers' working memory deficits that underlie poor reading comprehension are related to a general system, and (b) whether metacognition contributes to comprehension beyond what is predicted by working memory and word knowledge. To this end, performance between learning and disabled (N = 60) and average readers (N = 60) was compared on the reading comprehension, reading rate, and vocabulary subtests of the Nelson Skills Reading Test, Sentence Span test composed of high and low imagery words, and a Metacognitive Questionnaire. As expected, differences between groups in working memory, vocabulary, and reading measures emerged, whereas ability groups were statistically comparable on the Metacognitive Questionnaire. A within-group analysis indicated that the correlation patterns between working memory, vocabulary, metacognition, and reading comprehension were not the same between ability groups. For predicting reading comprehension, the metacognitive questionnaire best predicted learning disabled readers' performance, whereas the working memory span measure that included low-imagery words best predicted average achieving readers' comprehension. Overall, the results suggest that the relationship between learning disabled readers' generalised working memory deficits and poor reading comprehension may be mediated by metacognition.

Learning-disabled readers' working memory as a function of processing demands.

The purpose of this study was to investigate whether limitations in the enhancement of learning-disabled readers' working memory performance are attributable to process or storage functions. For Experiment 1, performance of reading-disabled, chronological age-matched, and reading level-matched children was compared on verbal and visual-spatial working memory measures under initial (no probes or cues), gain (cues that bring performance to an asymptotic level), and maintenance conditions (asymptotic conditions without cues). The results indicated that (a) learning-disabled readers' working memory performance was comparable on visual-spatial measures, but inferior to CA-matched children on verbal working memory measures; (b) learning-disabled readers' performance was superior to reading-matched counterparts across working memory conditions; and (c) performance differences remained between learning-disabled and CA-matched children or gain and maintenance conditions, even when initial and processing efficiency (probe) scores were partialed out in the analyses. Experiment 2 included the same conditions as Experiment 1, except that verbal short-term memory scores were also partialed out in the analysis. The results indicated that learning-disabled readers are inferior on both verbal and visual-spatial working memory measures when compared to CA-matched children on high demand conditions (maintenance). Two findings that emerged across experiments were (a) intercorrelations among diverse WM measures increased on demanding conditions and (b) verbal WM was not directly related to reading skill. In sum, the results support the notion that learning-disabled readers' poor working memory performance on demanding conditions reflect constraints in a central executive storage system.

Individual and age-related differences in children's working memory.

The purpose of this study was to investigate the degree to which age-related and individual differences in children's working memory (WM) are due to a general or task-specific capacity system. Experiment 1 correlated children's (N = 146; age range 5-19 years) verbal and visual-spatial working memory performance with various intelligence and achievement measures. The results supporting a general system were that (1) visual-spatial and verbal WM measures were significantly intercorrelated with and without age partialed out and (2) both verbal and visual-spatial WM measures were significantly correlated with diverse achievement and intelligence measures. Experiment 2 compared three age groups (N = 192; 7-, 10-, and 13-year-olds) on working-memory performance tasks under initial, enhanced (cued), and maintenance conditions. The results supporting a general capacity system were that (1) age-related performance differences in WM were found on all conditions and not isolated to specific processes, (2) the maintenance measures (high-load condition) predicted the variance better in age-related performance than process measures, and (3) although individual differences in WM performance reflected two independent operations, these operations produced similar correlations to achievement within age groups. Overall, the results support a general capacity explanation of age-related and individual differences in children's WM performance.

The relationship between intelligence and vigilance in children at risk.

The purpose of this study was to compare two competing models as an explanation of the relationship between intelligence and sustained attention in educationally at-risk kindergarten children. One model assumes that lower-IQ subjects allocate greater amounts of attentional resource of information-processing tasks than higher-IQ subjects, whereas the other model assumes that a "less-than" optimal level of arousal is associated with decrements in task performance across time. Twenty-nine teacher-nominated at-risk and 29 normal achieving kindergarten students were administered the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R) and vigilance taks. Signal detection measures of stimulus detectability (d'), decision criterion (beta), correct detections, and false alarms were used to assess children's sustained attention across three time periods (2, 4, and 6 min). The important results were (a) high-risk children were inferior on d' measures when compared to normal achieving children, (b) vigilance measures did not vary over time in either group, and (c) intelligence and vigilance shared a common factor in high-risk, but not low-risk, children. The results suggest that children educationally at risk suffer deficits related to attentional capacity for processing information.

Short-term memory and working memory: do both contribute to our understanding of academic achievement in children and adults with learning disabilities?

Seventy-five children and adults with learning disabilities (age range = 5.0 to 42.10 yrs.) and 86 normally achieving children and adults (age range = 5.11 to 58.0 yrs.) were compared on short-term memory (STM) and working memory (WM) tasks to assess the relationship between STM and WM, and to test whether these measures independently relate to achievement. For both ability groups, the factor analyses indicated that STM and WM loaded on different factors, and the regressions and partial correlations showed that these different factors accounted for separate variance in reading comprehension and mathematics. Both STM and WM are important in understanding reading comprehension and mathematics performance in children and adults with learning disabilities; however, WM is more important for children and adults without learning disabilities. In contrast to WM, STM contributed minimal variance to word recognition in both ability groups. Overall, it was concluded that STM and WM do reflect different processes, both of which seem to separate the two ability groups. However, models of memory that view STM and WM as interchangeable, or STM in isolation, do not provide an adequate framework for capturing academic performance in children and adults with learning disabilities.

Working memory in learning disability subgroups.

The purpose of this study was to investigate (a) the degree to which working memory differences between learning-disabled and nondisabled children reflect a specific or generalized deficit, and (b) whether limitations in the enhancement of learning-disabled student's working memory performance are attributable to process or storage functions. To this end, performances of reading-disabled, math-disabled, chronological age (CA)-matched, and achievement-matched children were compared on verbal and visual-spatial working memory measures under initial, gain, and maintenance conditions. The results indicated that: (a) learning-disabled subtypes were not differentiated by their performance on verbal and visual-spatial working memory measures; and (b) learning-disabled children's working memory performance was inferior to CA-matched and superior to achievement-matched counterparts across initial, gain, and maintenance conditions. The results suggest that learning-disabled children suffer generalized working memory deficits, possibly due to storage constraints in the executive system.