SEMANTIC INFLUENCES ON THEMATIC ROLE ASSIGNMENT - EVIDENCE FROM NORMALS AND APHASICS

We report two studies that examine the role of semantic influences in the assignment of thematic roles. Semantic factors were manipulated by contrasting sentences in which one noun argument was a plausible fill er of only one thematic role (e.g., the painting in The artist dislike d the painting) with sentences in which both noun arguments were plaus ible fillers of both thematic roles (e.g., The robin ate the insect). Subjects were required to make plausibility judgments to sentences pre sented auditorily. Experiment 1 examined RTs of normal subjects on the plausibility judg ment task. In Experiment 2, the same sentences were presented to aphasic patients identified as ''asyntactic'' comprehend ers. In Experiment 1, RTs were speeded by semantic constraints on them atic assignment, particularly when the role-constrained NP occurred ea rly in the sentence (as in The painting was disliked by the artist). T he aphasic performance patterns in Experiment 2 paralleled those of no rmal subjects, but in greatly exaggerated fashion. The patients exhibi ted high error rates on sentences where semantic constraints conflicte d with the syntactically based assignments, even on sentences with can onical (S-V-O) word order (e.g., #The deer shot the hunter). (C) 1998 Academic Press.