Towards a unified process model for graphemic buffer disorder and deep dysgraphia.

Models based on the competitive queuing (CQ) approach can explain many of the effects on dysgraphic patients' spelling attributed to disruption of the "graphemic output buffer". Situating such a model in the wider spelling system, however, raises the question of what happens when input to the buffer (e.g., from a semantic system) is degraded while the buffer remains intact. We present a preliminary exploration of predictions following from the CQ approach. We show that the CQ account of the graphemic buffer predicts and explains the finding that deep dysgraphic patients generally show features of graphemic buffer disorder, as disrupted input from a damaged semantic system has an inevitable effect upon the functioning of the buffer. The approach also explains the most salient differences between the two syndromes, which are seen as consequences of the difference between an intact sequence generation system operating on degraded input versus a damaged sequencing system operating on intact input.