From graphemes to abstract letter shapes: levels of representation in written spelling.

The letter substitution errors of 2 dysgraphic subjects who, despite relatively intact oral spelling, made well-formed letter substitution errors in written spelling, were studied. Many of these errors bear a general physical similarity to the intended target. Analyses revealed that this similarity apparently was based on the features of the component strokes of letters rather than on visuospatial characteristics. A comparison of these subjects' letter substitution errors with those of 2 other individuals with brain damage, whose damage was at a different level of processing, revealed that the latter subjects' errors are not explicable in terms of stroke-feature similarity. Strong support was found for the computation of multiple representational types in the course of written spelling. This system includes a relatively abstract, effector-independent representational level that specifies the features of the component strokes of letters.