Missing working memory deficit in dyslexia: children writing from memory

Missing working memory deficit in dyslexia: children writing from memory Erlijn van Genuchten a,b (e.w.vangenuchten@students.uu.nl) Peter C-H. Cheng b (p.c.h.cheng@sussex.ac.uk) Paul P. M. Leseman a (p.p.m.leseman@uu.nl) Marielle H. Messer a (m.h.messer@uu.nl) a Langeveld Institute, Utrecht University Utrecht, 3584 CS, NL b Department of Informatics, University of Sussex Brighton, BN1 9QJ, UK Abstract This research focused on the fluency of writing processes of children with dyslexia, in order to examine the relationship between WM and writing. An experiment was used in which children with dyslexia, and chronological age-matched and reading age-matched children without dyslexia wrote 24 sentences. Sentences with existing words and non-words were used. The results show that there are no differences between children with dyslexia and their chronological age-matched peers during writing. This similarity is surprising and indicates that WM problems in children with dyslexia may have no impact on their writing. The results imply that when different components of WM interact with each other, a model in which visuospatial and verbal WM are separated is more appropriate than a model with a pooled WM. Keywords: Temporal signal analysis, writing, working memory, dyslexia, sentences. Introduction The process of writing involves a large number of processes in different cognitive components. Therefore, understanding of how writers produce sentences includes an explanation of how activities are orchestrated in the cognitive system. Here, an important characteristic is the limited capacity of working memory (WM) to simultaneously maintain and process information (Olive, 2004). Children with dyslexia suffer from inefficient automatic information-handling processes (Turner, 1997), and have impaired WM (Berninger et al., 2006), and are therefore struggling with writing (Berninger, Abbott, Thomson, & Raskind, 2001). Another explanation for writing problems in children with dyslexia, is that these children have difficulties with phonological representations that stems (partly) from a phonological core deficit. Specifically, these children have difficulties with constructing, maintaining, and retrieving phonological representations (De Bree, 2007). This research focused on the fluency of writing processes of children with dyslexia, in order to examine the relationship between WM and writing. Working memory According to Baddeley (2000), WM consists of several components which work together to enable the active processing and preservation of information in memory (Gazzaniga, 2002). During writing, cognitive processes operate on different levels. For example, on a high level, visual WM stores the orthographic information of already written words, as an aid to catching spelling, or other errors (Kellogg, Olive, & Piolat, 2007). Also, WM is used to represent the physical layout of the text (Kellogg, Olive, & Piolat, 2007). On a lower level of representation, for example, spelling involves a number of functionally distinct processing components. According to a spelling framework described by Tainturier and Rapp (2001), the ability to generate a spelling for words relies on the phonology to orthography conversion system. In this system, words are segmented into smaller units (e.g., phonemes, syllables). These smaller units are then converted into orthographic units which are assembled into a correctly sequenced abstract letter string. These abstract strings do not have a specific format. This means that a specific modality and format of output should be chosen, which is handwriting in this research. Children with dyslexia are constrained by their WM limitations during writing, because they lack fluent text- generation processes (e.g., blending individual sounds to make a word) and writing-relevant knowledge (e.g., knowledge about which letter is associated to which sound). Therefore, these children may not have sufficient WM capacity to deal with the multiple demands imposed by the writing processes (McCuthen, 2000), causing the writing process to be slower and more laborious (Siegel, 2003). The writing process is even slower and more laborious in the case of sentences containing non-words, because the word identification process is more cumbersome. This is caused by the inability of children with dyslexia to rely on their mental lexicon during identification of a word (Siegel, 2003). Because of these increased processing demands, less capacity is left for storing words that should be written. Phonological core deficit Another problem reported in children with dyslexia is the phonological core deficit. According to this hypothesis, children with dyslexia code phonology in the brain less efficiently than children without dyslexia. This problem causes symptoms, such as difficulties with verbal short-term