The role of working memory in planning and generating written sentences

Abstract

Planning a sentence with concrete concepts whose referents can be mentally imaged has been shown in past work to require the limited resources of visual working memory. By contrast, grammatically encoding such concepts as lexical items in a syntactic structure requires verbal working memory. We report an experiment designed to demonstrate a double dissociation of these two stores of working memory by manipulating the difficulty of (1) planning by comparing related concepts to unrelated concepts and (2) grammatical encoding of an English sentence in active voice versus the more complex structure of the passive voice. College students (N = 46) composed sentences that were to include two noun prompts (related versus unrelated) while concurrently performing either a visual or a verbal distracting task. Instructions to produce either active or passive sentences were manipulated between groups. The results surprisingly indicated that the supposedly easier planning with related concepts made a large demand on verbal working memory, rather than unrelated concepts demanding more visual working memory. The temporal dynamics of the sentence production process appear to best account for the unexpected findings.