What limits working memory capacity? Evidence for modality-specific sources to the simultaneous storage of visual and auditory arrays.

Fougnie D, Marois R
J Exp Psychol Learn Mem Cogn. 2011 37 (6): 1329-41

PMID: 21859231 · PMCID: PMC4156106 · DOI:10.1037/a0024834

There is considerable debate on whether working memory (WM) storage is mediated by distinct subsystems for auditory and visual stimuli (Baddeley, 1986) or whether it is constrained by a single, central capacity-limited system (Cowan, 2006). Recent studies have addressed this issue by measuring the dual-task cost during the concurrent storage of auditory and visual arrays (e.g., Cocchini, Logie, Della Sala, MacPherson, & Baddeley, 2002; Fougnie & Marois, 2006; Saults & Cowan, 2007). However, studies have yielded widely different dual-task costs, which have been taken to support both modality-specific and central capacity-limit accounts of WM storage. Here, we demonstrate that the controversies regarding such costs mostly stem from how these costs are measured. Measures that compare combined dual-task capacity with the higher single-task capacity support a single, central WM store when there is a large disparity between the single-task capacities (Experiment 1) but not when the single-task capacities are well equated (Experiment 2). In contrast, measures of the dual-task cost that normalize for differences in single-task capacity reveal evidence for modality-specific stores, regardless of single-task performance. Moreover, these normalized measures indicate that dual-task cost is much smaller if the tasks do not involve maintaining bound feature representations in WM (Experiment 3). Taken together, these experiments not only resolve a discrepancy in the field and clarify how to assess the dual-task cost but also indicate that WM capacity can be constrained both by modality-specific and modality-independent sources of information processing.

MeSH Terms (17)

Acoustic Stimulation Adolescent Adult Analysis of Variance Attention Auditory Perception Color Perception Discrimination (Psychology) Female Humans Male Memory, Short-Term Neuropsychological Tests Photic Stimulation Psychophysics Reaction Time Young Adult

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