title: Shape and spatial working memory capacities are mostly independent.
abstract: Whether visual working memory (WM) consists of a common storage resource or of multiple subsystems has been a controversial issue. Logie (1995) suggested that it can be divided into visual (for color, shape, objects, etc.) and spatial WM (for location). However, a recent study reported evidence against this hypothesis. Using a dual task paradigm, Wood (2011) showed interference between shape and spatial WM capacities, suggesting that they share a common resource limitation. We re-examined this finding controlling possible confounding factors, including the way to present spatial location cues, task order, and type of WM load to be manipulated. The same pattern of results was successfully reproduced, but only in a highly powered experiment (N = 90), and therefore the size of interference was estimated to be quite small (d = 0.24). Thus, these data offer a way to reconcile seemingly contradicting previous findings. On the one hand, some part of the storage system is genuinely shared by shape and spatial WM systems, confirming the report of Wood (2011). On the other hand, the amount of the overlap is only minimal, and therefore the two systems should be regarded as mostly independent from each other, supporting the classical visuo-spatial separation hypothesis.
authors.affiliation: Department of Cognitive and Behavioral Sciences, Graduate School of Arts and Science, The University of Tokyo Tokyo, Japan ; Japan Society for the Promotion of Science Tokyo, Japan.
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Sanada
authors.affiliation: Japan Society for the Promotion of Science Tokyo, Japan ; Department of Psychology, Chukyo University Nagoya, Japan.
authors.forename: Koki
authors.initials: K
authors.lastname: Ikeda
authors.affiliation: Department of Cognitive and Behavioral Sciences, Graduate School of Arts and Science, The University of Tokyo Tokyo, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Hasegawa
keywords: dual task; spatial working memory; visual working memory; visuo-spatial sketchpad; working memory capacity