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.

Individual differences in working-memory (WM) capacity predicted performance on the Stroop task in 5 experiments, indicating the importance of executive control and goal maintenance to selective attention. When the Stroop task encouraged goal neglect by including large numbers of congruent trials (RED presented in red), low WM individuals committed more errors than did high WM individuals on the rare incongruent trials (BLUE in red) that required maintaining access to the "ignore-the-word" goal for accurate responding. In contrast, in tasks with no or few congruent trials, or in high-congruency tasks that followed low-congruency tasks, WM predicted response-time interference. WM was related to latency, not accuracy, in contexts that reinforced the task goal and so minimized the difficulty of actively maintaining it. The data and a literature review suggest that Stroop interference is jointly determined by 2 mechanisms, goal maintenance and competition resolution, and that the dominance of each depends on WM capacity, as well as the task set induced by current and previous contexts. Baddeley and Hitch (1974;Baddeley, 1986Baddeley, , 1993 proposed a "working memory" (WM) model that emphasized the dynamic interaction of memory maintenance and attention control in the service of complex cognition. In fact, individual-difference measures of WM capacity have turned out to be impressive predictors of a variety of cognitive abilities, including language comprehension, learning, and fluid reasoning (e.g., Daneman & Carpenter, 1980;Kyllonen & Christal, 1990;Shute, 1991;Süß, Oberauer, Wittman, Wilhelm, & Schulze, 2002). The present investigation explored the idea that the attentional, "executive" component of the WM system is specifically responsible for the covariation between measures of WM and higher order cognition (e.g., Engle, 2001Engle, , 2002Engle, Kane, & Tuholski, 1999).Our view is that simple memory ability, alone, cannot account for the strong association between WM span and complex cognition. Supporting evidence comes from structural-equationmodeling studies that tested participants in "span" tasks of WM and short-term memory (STM), as well as nonverbal tests of general fluid intelligence (Conway, Cowan, Bunting, Therriault, & Minkoff, 2002;Engle, Tuholski, Laughlin, & Conway, 1999). The WM span tasks required participants to maintain information online while they intermittently processed unrelated information. For example, the Operation Span (OSPAN) task (Turner & Engle, 1989) interleaved short series of words to be recalled with simple equations to be solved. The STM span tasks also required immediate recall of word lists, but unlike the WM tasks, they did not require any additional processing of unrelated information. WM and STM span tasks were strongly correlated with each other at the latent-construct level, reflecting that both involved the retention of unrelated words. However, only the WM construct correlated with a fluid-intelligence construct. The STM construct did not share unique variance with inte...

A latent-variable study examined whether verbal and visuospatial working memory (WM) capacity measures reflect a primarily domain-general construct by testing 236 participants in 3 span tests each of verbal WM, visuospatial WM, verbal short-term memory (STM), and visuospatial STM, as well as in tests of verbal and spatial reasoning and general fluid intelligence (Gf). Confirmatory factor analyses and structural equation models indicated that the WM tasks largely reflected a domain-general factor, whereas STM tasks, based on the same stimuli as the WM tasks, were much more domain specific. The WM construct was a strong predictor of Gf and a weaker predictor of domain-specific reasoning, and the reverse was true for the STM construct. The findings support a domain-general view of WM capacity, in which executive-attention processes drive the broad predictive utility of WM span measures, and domain-specific storage and rehearsal processes relate more strongly to domain-specific aspects of complex cognition.

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In 2 experiments the authors examined whether individual differences in working-memory (WM) capacity are related to attentional control. Experiment I tested high-and low-WM-span (high-span and low-span) participants in a prosaccade task, in which a visual cue appeared in the same location as a subsequent to-beidentified target letter, and in an antisaccade task, in which a target appeared opposite the cued location. Span groups identified targets equally well in the prosaccade task, reflecting equivalence in automatic orienting. However, low-span participants were slower and less accurate than high-span participants in the antisaccade task, reflecting differences in attentional control. Experiment 2 measured eye movements across a long antisaccade session. Low-span participants made slower and more erroneous saccades than did high-span participants. In both experiments, low-span participants performed poorly when task switching from antisaccade to prosaccade blocks. The findings support a controlled-attention view of WM capacity. Article:In 1980, Daneman and Carpenter provided the first demonstration of strong correlations among measures of immediate memory and complex cognition. Their working-memory (WM) span tasks, reading span and listening span, required participants to maintain a short list of words in memory while simultaneously reading or hearing sentences that contained the target words. Thus, the critical task-a memory-span test-was embedded within a secondary comprehension task. Daneman and Carpenter found that performance on these span tasks correlated with a global reading comprehension measure (the verbal Scholastic Aptitude Test [SAT]) with rs ranging from .49 to .59 and with more local comprehension measures (answering factual and pronoun-reference questions about prose passages) with rs ranging from .42 to .90. These impressive correlations stood in stark contrast to previous failures to correlate language comprehension with traditional short-term memory measures, such as digit span and word span, which placed minimal processing demands on the participant (for reviews see Crowder, 1982;Perfetti & Lesgold, 1977). Attempts to understand the relation between working-memory capacity and higher-order cognition have occupied researchers for the past 20 years and they are the focus of the present investigation. Carpenter (1980, 1983) hypothesized that individual differences in reading efficiency mediated both individual differences in their span task and the correlations between span and comprehension. They assumed that WM capacity was a limited resource that could be allocated to processing functions, storage functions, or both (see Baddeley & Hitch, 1974), and that participants who more efficiently processed the sentences of the span task had more capacity remaining to store the sentence-ending target words. By this view, WM capacity, or the amount of information that can be stored during processing, is tied to the specific processing demands of the concurrent task. Good readers have more storage cap...