Tuesday, May 20, 2008

IQ Research Bytes # 3: Working memory in recent Intelligence issues

I give up. I can't keep up with the sheer mass of working-memory research articles I acquire, with the full intention of reading and make blog comment posts. There is simply tooooooo much being published. My prior post today (Working memory research is hot) provides links to all IQ's Corner working memory posts and a fresh working memory reference bibliography.

Below are working-memory articles (reference and abstracts only) that were either in the latest issue of Intelligence or are "in press" in the journal. If someone wants to take the time to read one or more of these articles and produce a guest Virtual Scholars blog post, I'd be willing to provide the volunteers with access to the articles off-line. Contact me via email if you are interested in helping keep readers abreast of recent research in this area.

Vock, M & Holling, H (2008). The measurement of visuo–spatial and verbal–numerical workingmemory: Development of IRT-based scales. Intelligence, 36, 161–182
  • The objective of this study is to explore the potential for developing IRT-based working memory scales for assessing specific working memory components in children (8–13 years). These working memory scales should measure cognitive abilities reliably in the upper range of ability distribution as well as in the normal range, and provide a much-needed, reliable, and valid test for assessing high intellectual abilities in children. Six computer-assisted working memory tasks were administered to 172 children from regular schools and to 202 children from special schools and other institutions for the gifted. A factor analysis revealed a two-factor structure and the existence of a verbal–numerical and a visuo–spatial working memory scale. Classical item analysis and IRT analysis yielded good psychometric properties for both scales and revealed that the scales are appropriate for measuring high cognitive abilities. Both scales showed substantial and differential power for the explanation of variance in school achievement.
Lynn, R. & Iwring, P. (2008). Sex differences in mental arithmetic, digit span, and g defined as working memory capacity. Intelligence, 36, 226–235

  • Meta-analyses are presented of sex differences in (1) the (mental) arithmetic subtest of the Wechsler intelligence tests for children and adolescents (the WISC and WPPSI tests), showing that boys obtained a mean advantage of .11d; (2) the (mental) arithmetic subtest of the Wechsler intelligence tests for adults (the WAIS tests) showing a mean male advantage of .47d; (3) the digit span subtest of the Wechsler intelligence tests for children and adolescents (the WISC and WPPSI tests), showing that girls obtained a mean advantage of .134d; (4) the digit span subtest of the Wechsler intelligence tests for adults (the WAIS tests) show in a male advantage of .116d among adults. These results show that the sex differences on mental arithmetic are not consistent with the sex differences on digit span. It is proposed that the reason for this is that mental arithmetic is a measure of working memory capacity while digit span is a measure of immediate memory capacity. If this is accepted, the results indicate that there is virtually no sex difference in immediate memory capacity (measured by digit span) but a small male advantage among children and a substantial male advantage among adults in working memory capacity (measured by mental arithmetic). The results are further interpreted in terms of Kyllonen's theory that working memory capacity is g. If this is accepted, it follows that males have an advantage in g and that the higher average means obtained by men in IQ tests like the WAIS and the Progressive Matrices is attributable to their advantage in g.
Colom, R. et al. (2008, in press). Working memory and intelligence are highly related constructs, but why?
  • Working memory and the general factor of intelligence (g) are highly related constructs. However, we still don't know why. Some models support the central role of simple short-term storage, whereas others appeal to executive functions like the control of attention. Nevertheless, the available empirical evidence does not suffice to get an answer, presumably because relevant measures are frequently considered in isolation. To overcome this problem, here we consider concurrently simple short-term storage, mental speed, updating, and the control of attention along with working memory and intelligence measures, across three separate studies. Several diverse measures are administered to a total of 661 participants. The findings are consistent with the view that simple short term storage largely accounts for the relationship between working memory and intelligence. Mental speed, updating, and the control of attention are not consistently related to working memory, and they are not genuinely associated with intelligence once the short-term storage component is removed.
Oberauer, K. et al. (2008, in press). Which working memory functions predict intelligence? Intelligence.
  • Investigates the relationship between three factors of working memory (storage and processing, relational integration, and supervision) and four factors of intelligence (reasoning, speed, memory, and creativity) using structural equation models. Relational integration predicted reasoning ability at least as well as the storage-and-processing construct. Supervision, measured as specific switch costs, was not related to intelligence, but general switch costs were moderately correlated to the reasoning factor. The results question the view of working memory as a device for storage and processing, and the executive-attention account of working memory. They are better explained by theories describing working memory as a system for building relational representations through temporary bindings between component representations.
Tillman, C. (2008, in press). Working memory components and intelligence in children. Intelligence.

  • This study investigated, in children aged 6–13 years, how different components of the working memory (WM) system (short-term storage and executive processes), within both verbal and visuospatial domains, relate to fluid intelligence. We also examined the degree of domain-specificity of the WM components as well as the differentiation of storage and executive components. The short term memory (STM) and WM tasks used allowed us to statistically separate the executive from the storage processes, enabling examination of separate processes in relation to intelligence. Our results demonstrated that all four WM components (verbal- and visuospatial short-term storage and verbal- and visuospatial executive processes) provided significant, independent contributions to intelligence, indicating that, in children, both storage and executive processes of the WM system are relevant to intelligence. Especially intriguing are our findings showing that verbal and visuospatial executive processes independently predicted intelligence, suggesting that, in children, the executive processes may rely on separate resources for the verbal and visuospatial domains.

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