Pergamon J. Neurdinguisrics. Vol. 8. No. I. pp. 19-Z. 1994 Copyright 01994 Elsevier Science Ltd Printed in Great Britain. All rights reserved 091 l-6044/94 $7.00+0.00 HOW TWO APHASIC SPEAKERS CONSTRUCT SUBJECT-VERB AGREEMENT GABRIELLA VIGLICICCO,* BRIAN BUTTERWORTH,? $ CARLO SEMENZA~ and SABRINA FOSSELLA~ *Department of Psychology, University of Trieste, Italy; tDepattment of Psychology, University College London, U.K.; and #Department of General Psychology, University of Padova, Italy Abstract-The processes by which two aphasics constructed subject-verb agreement in speech were examined using two experiments in which subjects had to complete a sentence preamble (Bock and Miller, Cognifive Psychology 23, 35-43, 1991). Both patients had good comprehension and performed at similar level, though significantly worse than normal, in the first experiment. In the second experiment, one aphasic, classified as agrammatic, showed normal sensitivity to semantic and morphological variables in the preamble. The second patient, classified as conduction aphasic, showed sensitivity to neither variable. The theoretical implications of a selective inability to make use of semantic and morphological information are discussed. INTRODUCTION PRODUCING SVA involves the speaker accessing a complex set of information, namely the morphology of the verb conjugations. Access is itself under the control of a complex set of processes that involve the selection of a discourse element to be the subject of the sentence, selection of a suitable noun to be the head of subject NP, identification of diacritical parameters of N, e.g. number and gender, that may be relevant to SVA, selection of the head of VP, and transfer of diacritical parameters of the subject to the process of selecting the appropriate morphological form of the V. Despite this, producing SVA is usually error free. Even patients who make many para- grammatic errors, make less than 3.5 errors per 100 opportunities to do so [l] . However, the presence of an “attractor” N in the subject NP can induce spontaneous speech (or writing) errors of the sort shown in (1) (1) a. The readiness of our conventional forces ARE at an all time low b. Learning skills in people entering college IS less than it should be (from BOCK and MILLER [2]) Such errors are quite common in free speech and some linguists have even given them special names-attraction errors [ 31, proximity concord [ 41. In a series of sentence completion experiments Bock and her colleagues have demonstrated that when the Head and Attractor Ns differ in grammatical number, the rate of SVA errors increases [2,5,6] . In a typical experiment, subjects were presented with a preamble in which *Author to whom correspondence should be addressed at: Department of Psychology, University College London, Gower Street, London WClE 6BT, U.K. 19