Stimulus similarity decrements in children’s working memory span. The Quarterly

Two experiments investigated the impact of the relationship between processing and storage stimuli on the working memory span task performance of children aged 7 and 9 years of age. In Experiment 1, two types of span task were administered (sentence span and operation span), and participants were required to recall either the products of the processing task (sentence-final word, arithmetic total) or a word or digit unrelated to the processing task. Experiment 2 contrasted sentence span and operation span combined with storage of either words or digits, in tasks in which the item to be remembered was not a direct product of the processing task in either condition. In both experiments, memory span was significantly greater when the items to be recalled belonged to a different stimulus category from the material that was processed, so that in sentence span tasks, number recall was superior to word recall, and in operation span tasks, word recall was superior to number recall. Explanations of these findings in terms of similarity-based interference and response competition in working memory are discussed. Working memory is widely believed to be responsible for the ability to store and manipulate information for brief periods of time. Its capacity is commonly measured by complex span tasks, in which participants are required to combine processing activities with the short-term retention of information. One such task is reading span, which involves processing a series of sentences for meaning while retaining the sentence-final words for subsequent recall (Daneman & Carpenter, 1980). Variations of the reading span task, such as counting span (Case, Kurland, & Goldberg, 1982), operation span (Turner & Engle, 1989), and spatial span (Shah & Miyake, 1996) are also widely used. Performance on such tasks is strongly related to higher level cognitive activities such as reasoning and reading comprehension (e.g., Engle, Cantor, & Carullo, 1992; Kyllonen & Christal, 1990) and also academic achievement (e.g., Gathercole