The relationship of domain-general serial order memory and reading ability in school children with and without dyslexia.

Recent evidence suggests that reading development when learning alphabetic languages is related to the underlying cognitive ability to maintain the serial order of information in short-term memory (STM). However, it remains unclear at which time point in reading development serial order STM is most important. Here, we established a crucial link between the reading development of primary school children and their serial order STM performance for both verbal and nonverbal materials. In a large cohort study of 113 Italian-speaking elementary school children in Grades 1-4, we investigated this relationship by implementing a novel double-probe design. In Experiment 1, we found that serial order STM performance was related to children's reading abilities, especially in Grades 2 and 3, corresponding to the training phase of grapheme-phoneme decoding skills. In Experiment 2, we assessed children with developmental dyslexia (DD) and found that their serial order STM performance was significantly lower than that of chronological age-matched controls (CA). It also differed from that of reading age-matched controls when accounting for individual reading performance. Furthermore, the CA group displayed an implicit serial order facilitation for item memory, whereas this implicit recruitment of serial order abilities was completely absent in children with DD. Our results suggest that the domain-general cognitive ability to maintain the serial order of information interacts with the development of reading competency, especially during a middle training phase of word reading, and this particular relationship is markedly impaired in children with DD.