A cognitive-neuropsychological analysis of allograph errors from a patient with acquired dysgraphia

Abstract

This paper reports an investigation of the impaired writing of an acquired dysgraphic patient J.E.C. who made several case, substitution, omission, and addition errors when writing lower-case letters cursively, but whose upper-case writing was intact. The main finding was that damage to the lower-case letter production system results in errors that can be predicted from the spatial similarity of the lower-case form of the error to the lower-case form of the target. This was found with both within-case and cross-case letter substitutions. An additional observation was consistent cross-case errors occurred only with targets forming a single cluster of spatially similar lower-case letters (b, d, p, and q). It is concluded access to lower-case letters is constrained by spatial similarity of a target to other letters in allograph store, and this effect may explain letter errors made by dysgraphic patients.