Development of Visual-verbal Integration in Working Memory during Childhood and its Relation to Language and Reading

Research has demonstrated working memory improves during childhood and supports vocabulary, grammar, and reading development (Adams & Gathercole, 1995, 1996; Bowey, 1996; Gathercole & Baddeley, 1989, 1990). Prior to the addition of the episodic buffer in Baddeley’s model of working memory (2000a), auditory and visual aspects of working memory were often treated separately without evaluating contributions from the ability to integrate the two forms of information. The present study was designed to investigate the development of visual-verbal integration in working memory and its role in language and reading development. Tests of receptive vocabulary, receptive grammar, and decoding ability were administered to 46 children between 6 and 10 years of age. Working memory was assessed with a paired associates task where stimuli varied based on modality and contributions from long-term memory were limited by using nonwords and unfamiliar images. Data from the same tests of language and working memory were also available for 58 children between 3 and 5 years of age (Robinson & Smith, 2005) and included in exploratory analyses. Developmental findings were consistent with previous studies in indicating the unimodal aspects of working memory improve steadily across the entire age range examined. Growth curve analyses of cross-modal working memory, which taxed the episodic buffer, showed curvilinear growth where spans increased rapidly between 3 and 7 years of age then appeared to slow dramatically. Analyses of residuals support the notion of integrative growth above and beyond changes in unimodal working memory. Although cross-modal working memory did not make significant contributions to decoding ability, it accounted for 11% of unique variance in receptive grammar scores in school-aged children