Central and Peripheral Components of Working Memory Storage

This study reexamines the issue of how much of working memory storage is central, or shared across sensory modalities and verbal and nonverbal codes, and how much is peripheral, or specific to a modality or code. In addition to the exploration of many parameters in 9 new dual-task experiments and reanalysis of some prior evidence, the innovations of the present work compared to previous studies of memory for 2 stimulus sets include (a) use of a principled set of formulas to estimate the number of items in working memory and (b) a model to dissociate central components, which are allocated to very different stimulus sets depending on the instructions, from peripheral components, which are used for only 1 kind of material. We consistently find that the central contribution is smaller than was suggested by Saults and Cowan (2007) and that the peripheral contribution is often much larger when the task does not require the binding of features within an object. Previous capacity estimates are consistent with the sum of central plus peripheral components observed here. We consider the implications of the data as constraints on theories of working memory storage and maintenance.