Working Memory Span Tasks: A Methodological Review and User's Guide

Article excerpt

Working memory (WM) span tasks-and in particular, counting span, operation span, and reading span tasks-are widely used measures of WM capacity. Despite their popularity, however, there has never been a comprehensive analysis of the merits of WM span tasks as measurement tools. Here, we review the genesis of these tasks and discuss how and why they came to be so influential. In so doing, we address the reliability and validity of the tasks, and we consider more technical aspects of the tasks, such as optimal administration and scoring procedures. Finally, we discuss statistical and methodological techniques that have commonly been used in conjunction with WM span tasks, such as latent variable analysis and extreme-groups designs.

Other than standardized instruments, such as intelligence test batteries, working memory (WM) span tasks, such as the counting span, operation span, and reading span tasks, are among the most widely used measurement tools in cognitive psychology. These tasks have come to prominence not only for their methodological merit, but also because theoretical advances in the study of human behavior since the cognitive revolution have placed WM as a central construct in psychology. Methodologically, WM span tasks have proven to be both reliable and valid measures of WM capacity (WMC), which we will document below. However, the larger factor in accounting for their increased use is simply that WM has become a widely useful, scientifically fruitful construct. It plays an important role in contemporary global models of cognition (e.g., J. R. Anderson & Lebiere, 1998; Cowan, 1995), and it is purportedly involved in a wide range of complex cognitive behaviors, such as comprehension, reasoning, and problem solving (Engle, 2002). Also, WMC is an important individual-differences variable and accounts for a significant portion of variance in general intellectual ability (Conway, Cowan, Bunting, Therriault, & Minkoff, 2002; Conway, Kane, & Engle, 2003; Engle, Tuholski, Laughlin, & Conway, 1999; Kane et al., 2004; Kyllonen, 1996; Kyllonen & Christal, 1990; SuB, Oberauer, Wittmann, WilhElm, & Schulze, 2002). Furthermore, neuroimaging and neuropsychological studies have revealed that WM function is particularly dependent on cells in the prefrontal cortex of the brain, which has traditionally held a prominent status in the biological approach to studying complex goal-directed human behavior (Kane & Engle, 2002).

A diverse set of researchers is now using WM as a construct in research programs, as well as measures of WMC in the arsenal of research tools. Within psychology, discussions of WM are now common in almost all branches of the discipline, including cognitive, clinical, social, developmental, and educational psychology. For example, clinical research has demonstrated that WM is related to depression (Arnett et al., 1999) and to the ability to deal with life event stress (Klein & Boals, 2001 ) and is affected by alcohol consumption (Finn, 2002). Social psychologists have revealed that students under stereotype threat suffer reduced WMC and that WMC mediates the effect of stereotype threat on standardized tests (Schmader & Johns, 2003). Also, WMC is taxed and, subsequently, depleted as a result of interracial interaction for highly prejudiced individuals (Richeson et al., 2003; Richeson & Shelton, 2003). In neuropsychology, deficits in WMC may be a marker of early onset of Alzheimer's disease (Rosen, Bergeson, Putnam, Harwell, & Sunderland, 2002). Developmental research suggests that the development of WMC in children is central to the development of cognitive abilities in general (Munakata, Morton, & O'Reilly, in press) and that declines in WMC as a result of aging are central to general cognitive-aging effects (Hasher & Zacks, 1988). In short, recent research across the discipline implicates WM as a central psychological construct (for reviews, see Feldman-Barrett, Tugade, & Engle, 2004; Unsworth, Heitz, & Engle, 2005). …