Is Working Memory Storage Intrinsically Domain-Specific?

It has recently been claimed that working memory (WM) storage is intrinsically domain-specific because the concurrent maintenance of an auditory and a visuospatial memory set did not involve any dual-task cost (Fougnie, Zughni, Godwin, & Marois, 2015). Using the same paradigm, we asked participants to concurrently maintain verbal auditory memory sets of 2, 4, or 6 letters along with visuospatial memory sets of 1, 3, or 5 dots in spatial locations. Whereas using the probe-recognition procedure used by Fougnie, Zughni, Godwin, and Marois (2015) replicated the absence of dual-task cost, a recall procedure revealed systematic interference between auditory-verbal and visuospatial WM. Increasing verbal WM load had a detrimental effect on the recall of visuospatial information, and vice versa, whether or not the task was performed under concurrent articulation. These between-domain interference effects proved to be non-negligible in magnitude when compared with within-domain effects in both the verbal (letters and digits) and visuospatial (spatial locations and movements) domains. The implication of these findings for our understanding of the structure and functioning of WM as well as the potential impact of the methods used to assess WM storage (i.e., recognition vs. recall) are discussed.