This study investigated the differential contribution of auditory-verbal and visuospatial working memory (WM) on decoding skills in second- and fifth-grade children identified with poor decoding. Thirty-two second-grade students and 22 fifth-grade students completed measures that assessed simple and complex auditory-verbal and visuospatial memory, phonological awareness, orthographic knowledge, listening comprehension and verbal and nonverbal intelligence. Bivariate correlations revealed that complex auditory-verbal WM was moderately and significantly correlated to word attack at second grade. The simple auditory-verbal WM measure was moderately and significantly correlated to word identification in fifth grade. The complex visuospatial WM measures were not correlated to word identification or word attack for second-grade students. However, for fifth-grade participants, there was a negative correlation between a complex visuospatial WM measure and word attack and a positive correlation between orthographic knowledge and word identification. Different types of WM measures predicted word identification and word attack ability in second and fifth graders. We wondered whether the processes involved in visuospatial memory (the visuospatial sketchpad) or auditory-verbal memory (the phonological loop), acting alone, would predict decoding skills. They did not. Similarly, the cognitive control abilities related to executive functions (measured by our complex memory tasks), acting alone, did not predict decoding at either grade. The optimal prediction models for each grade involved various combinations of storage, cognitive control, and retrieval processes. Second graders appeared to rely more on the processes involved in auditory-verbal WM when identifying words, while fifth-grade students relied on the visuospatial domains to identify words. For second-grade students, both complex visuospatial and auditory-verbal WM predicted word attack ability, but by fifth grade, only the visual domains predicted word attack. This study has implications for training instruction in reading. It was not the individual contributions of auditory-verbal or visuospatial WM that best predicted reading ability in second and fifth grade decoders, but rather, a combination of factors. Training WM in isolation of other skills does not increase reading ability. In fact, for young students, too much WM storage can interfere with learning to decode
