Individual differences in the fan effect and working memory capacity

In opposition to conceptualizing working memory (WM) in terms of a general capacity, we present four experiments that favor the view that individual differences in WM depend on attentional control. High- and low-WM participants, as assessed by the operation span task, learned unrelated sentences for which the subject and predicate of the sentences shared concepts (fan). Sentences were learned in sets organized by subjects (Experiments 1A and 1B) or predicates (Experiments 2A and 2B). WM predicted accuracy and reaction times on a subsequent speeded verification task, but not learning. In Experiments 1A and 2A, low-WM participants had a steeper, positively sloped fan effect for reaction times to studied items than high-WM participants. In Experiments 1B and 2B, fan was eliminated across but not within memory sets, which eliminated individual differences but not slope to the fan effect. These effects suggest the crux of WM is attentional control, and competition across sets causes individual differences. (C) 2004 Elsevier Inc. All rights reserved.