Working memory, but not IQ, predicts subsequent learning in children with learning difficulties

Research Institution: University of Durham, United Kingdom

Research title: Working memory, but not IQ, predicts subsequent learning in children with learning difficulties

Researcher: Tracy Packiam Alloway

Published: European Journal of Psychological Assessment, 2009 Volume 25

This study examined whether working memory and IQ both predicted reading and math achievement in 37 school age children identified as having learning difficulties. At baseline, children completed tests of IQ and WM along with a standardized achievement measure in reading and math. Two years later, the reading and math tests were repeated. Results indicated that after controlling for prior reading achievement, WM at baseline – but not IQ – was a significant predictor of reading ability. Comparable results were obtained for math. These findings highlight the importance of WM in the academic progress made by children with learning difficulties as well as the importance of targeting WM deficits as a target of intervention.

Working memory (WM) refers to the capacity to store and manipulate information for brief periods of time. Students with WM impairments often struggle in the classroom because “losing crucial information from working memory will cause them to forget many things: instructions they are attempting to follow, the details of what they are doing, where they have got to on a complicated task, and so on.” In fact, multiple studies have documented that WM deficits constrain children’s academic achievement and that many children with significant learning difficulties show impaired WM.

Another important determinant of academic achievement is IQ, and a strong correlation exists between children’s IQ and their academic success. Some researchers have suggested that IQ accounts for the apparent link between WM and academic achievement, and that WM makes no independent contribution to children’s academic success after its association with IQ is taken into account. The goal of this study was to test this hypothesis and learn whether WM is a significant predictor of academic achievement even when achievement differences related to IQ are controlled for.

Participants were 37 children between the ages of 7 and 11 at the start of the study; all had been identified as having significant learning difficulties. Working memory capacity was measured at baseline using the Automated Working Memory Assessment, a standardized and computerized measure of WM. For the purpose of this study, children’s verbal WM score, and not their visuo-spatial WM score, was computed. Verbal and performance IQ scores were measured using the WISC-III, a widely used IQ test. Academic achievement in reading and math were measured using the Wechsler Objective Reading Dimensions test and the Wechsler Objective Numerical Dimensions test, standardized measures of achievement in each area. Children were retested with these achievement measures two years later.

This design enable the author to test whether achievement at the 2 year follow-up was predicted by the earlier assessments of verbal WM, verbal and performance IQ, and achievement level in reading and math.

Results
Reading achievement at follow up was predicted by children’s initial reading level and their baseline verbal WM score. This means that after controlling for prior reading ability and IQ, children with better working memory became better readers. However, neither verbal nor performance IQ was a significant predictor of reading level at follow-up. Similarly, math achievement at follow-up was predicted by children’s math and verbal WM score at baseline. Once again, neither verbal nor performance IQ was a significant predictor.

Summary and Implications
Results from this study indicate that achievement in math and reading is predicted not only by earlier math and reading level, but also by verbal WM. These results provide strong evidence that WM contributes to the development of children’s reading and math abilities over time, apparently to a greater extent than their intellectual level.

While these findings highlight the importance of WM in academic achievement, they should not be interpreted to mean that intelligence does not matter for children’s academic performance, as this is certainly not the case. Instead, it may be that the influence of IQ on achievement was already captured in children’s achievement score at baseline, and that IQ did not contribute to subsequent achievement beyond this initial influence. In contrast, WM was both related to academic achievement at baseline, and also predicted achievement scores two years later.

This underscores the importance of identifying WM deficits in children and providing interventions – both through working memory training to enhance capacity, and teaching strategies tailored to children with poor working memory to ameliorate the academic difficulties these children are otherwise likely to experience.