THE INTERACTION OF LEXICAL AND SUBLEXICAL PROCESSES IN READING, WRITING AND REPETITION

It has recently been proposed that in the course of repetition, readin g aloud and writing to dictation, lexical representations are activate d and selected for output by the joint operation of the semantic syste m and of sublexical conversion mechanisms-the Summation Hypothesis [HI LLIS and CARAMAZZA, Brain Lang. 40, 106-144, 1991]. The hypothesis pre dicts that semantic errors in oral reading and in writing to dictation should only occur when both the semantic system and the sublexical co mponent involved in that task (orthography to phonology and phonology to orthography conversion, respectively) are damaged. The performance of Italian patient E.C.A. indicates damage to the semantic system, and to sublexical phonology to phonology and phonology to orthography con version mechanisms, but with substantial sparing of sublexical orthogr aphy to phonology conversion processes. In agreement with expectations derived from the Summation Hypothesis, E.C.A. produced semantic error s in repetition and in writing to dictation, but not in reading aloud. The paucity of semantic errors in speakers of languages with relative ly transparent orthographies is discussed in the context of the Summat ion Hypothesis.