Selective deficit in processing double letters.

This paper reports a patient with a selective difficulty in spelling words and pseudowords with geminate (double) consonants. In all writing tasks, deletions of a geminate consonant occurred ten times more often than deletions of a consonant in a non-geminate cluster. In addition, the probability of substituting both geminate consonants was indistinguishable from the probability of substituting one consonant in a non-geminate cluster; and, the probability of substituting only one geminate consonant was close to zero, and significantly lower than the probability of substituting one consonant in a non-geminate cluster. This pattern of performance is consistent with the hypothesis that grapheme quantity and identity are separately represented in orthographic representations. The fact that these errors occurred in the absence of a significant number of geminate transpositions is interpreted as support for the hypothesis that letter gemination is specified by a "doubling feature."