Developmental increase in working memory span: Resource sharing or temporal decay?

Working memory span tasks require participants to maintain items in short-term memory while performing some concurrent processing (e.g., reading, counting, and problem solving). It has been suggested that the difficulty of these tasks results either from the necessity of sharing a limited resource pool between processing and storage (Case's cognitive space hypothesis) or from the Fact that the memory traces suffer from a temporal decay while the concurrent task is being performed (Towse and Hitch`s memory decay hypothesis). We tested these two hypotheses by comparing children's performance in tasks in which the processing component always had the same duration but varied in cognitive cost (counting or problem solving vs repeatedly saying "baba"). The results indicate that both time and limitation of resources constrain performance in working memory tasks. We discuss their implications regarding current models of working memory. (C) 2001 Academic Press.