On the interplay between maintenance systems in verbal working memory

• Two systems (a specific and a general) maintain verbal items in working memory. • The Maxispan instructions control their joint use for a single series of items. • Maxispan instructions improve immediate recall and memory spans. • When the specific system is overloaded, the general system takes over. • Hence, this overload reduces the capacity of the general system. Most models of working memory (WM) include two systems for maintaining verbal information: one specific using verbal rehearsal and the other, general-purpose, relying on attention. These systems have been studied independently, but little is known about their interplay. The present study aimed at examining their interaction, especially when the verbal specific system is overloaded. Our hypothesis was that, in such a case, the attention-based system takes over, hence depleting attentional resources for maintenance. Though previously mentioned, this hypothesis has never been formally tested. We took advantage of a new methodology based on the Maxispan instructions, which controls the involvement of each system in immediate serial recall tasks. In the Maxispan instructions, participants cumulatively rehearse orally a defined number of the earlier items until recall, while also memorizing the subsequent items. Their performance was compared to that obtained in the regular instructions condition (i.e., no specific instructions). The articulatory demand of the verbal specific system was also manipulated by presenting either monosyllabic or trisyllabic words or pseudowords. Across five experiments, results supported our hypotheses. Maxispan (vs. regular) instructions led to improved recall performance for both rehearsed and non-rehearsed items. Importantly, rehearsing more syllables in the Maxispan instructions impaired maintenance of the later non-rehearsed items, bringing their recall close to the level of the regular instructions condition. These findings shed light on the interplay between the two systems of verbal maintenance, constraining WM models. Moreover, some peculiarities in words recall questioned the role of semantics in WM.