Delays of retention, processing efficiency, and attentional resources in working memory span development

Working memory span tasks require participants to maintain items in short-term memory while performing some concurrent processing (e.g., reading, counting, or problem solving). The present series of experiments contrasted two models of the development of working memory spans in children. Is this development mainly due to faster completion of the processing component in older children, as Towse and Hitch (1995) suggested, or is it due to resource-related phenomena such as increased processing efficiency and a greater amount of available cognitive resources? Using new computer-paced working memory span tasks that allow a careful control of processing duration, we demonstrate that the cognitive load of the processing component is more important than its total duration in determining working memory spans in children. Moreover, we provide evidence that even when both the duration and the difficulty of the intervening task are equated across age, working memory spans still exhibit a developmental increase that could be underpinned by a greater amount of cognitive resources in older children. (C) 2004 Elsevier Inc. All rights reserved.