Is there someone who have already investigated this issue with or without success? There is very few studies on this issue, especially regarding the orthographic influence on auditory STM tasks. Yet, orthographic representations are highly connected with phonological representations and may be activated during speech processing. Therefore, orthographic knowledge might help the recall of the words or non-words in certain situations (e.g., in case of phonologic similarity but orthographic dissimilarity as it has been showed in Pattamadilock et al. 2010).
Maybe some of you have tried to investigate this question in a different way ? Or more generally, have examined if reading acquisition influences the development of WM or verbal STM (that's my question of research)