Serial position effects in graphemic buffer impairment : An insight into components of orthographic working memory

This study investigated the nature of graphemic buffer functioning and impairment, through analysis of the spelling impairment shown by GEC, a man with acquired dysgraphia and clear characteristics of graphemic buffer impairment. We discuss GEC’s error patterns in relation to different processes of orthographic working memory. This is the first study to show the contribution of these processes in one individual through performance on different spelling tasks. GEC’s spelling errors in writing to dictation showed a linear serial position effect, including deletions of final letters. These “fragment errors” can be explained as the result of information rapidly decaying from the buffer (reduced temporal stability). However, in tasks that reduced working memory demands, GEC showed a different error distribution that may indicate impairment to a different buffer process (reduced representational distinctiveness). We argue that different error patterns can be a reflection of subcomponents of orthographic working memory that can be impaired separately.

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Funding: During the preparation of this paper, Trudy Krajenbrink was funded by an International Macquarie University Research Excellence Scholarship (IMQRES 2011045), Lyndsey Nickels by an Australian Research Council Future Fellowship (FT120100102), and Saskia Kohnen by a Macquarie University Research Fellowship (MQRF).