LEXICAL CONSTRAINTS AND PREPOSITIONAL PHRASE ATTACHMENT

Six experiments investigated how lexical constraints influence syntact ic analysis during an ambiguous region of an isolated sentence. We foc used on prepositional phrase (PP) attachment ambiguities in dative sen tences such as ''John gave a letter to his son...'' to test some predi ctions of constraint-based lexicalist models. Processing difficulty wa s measured using word-by-word sensibility judgments (Experiments 1-3 a nd 5) and word-by-word reading times (Experiments 4 and 6). We found t hat both the timing and the type of lexical constraint information gov erned how it was used. A syntactic commitment was made early in the am biguous region when one structure was supported by multiple constraint s at the point of ambiguity. Thus, garden path effects were found for both ''John gave a letter to his son to a friend'' and ''Paul gave the script to the play to a girl.'' (the locally ambiguous PP is italiciz ed). The amount of processing difficulty experienced during the second PP was greatly reduced when the preposition in the first prepositiona l phrase was inconsistent with the verb's constraints on ''recipient'' PP's (e.g.,''John gave a letter for/about his son to a friend''). In contrast, manipulating probabilistic constraints of the preposition ha d little effect on either judgments or reading times. These results su pport a constraint-based view of parsing in which those constraints th at are encoded in competing lexical forms influence the strength with which syntactic alternatives are made available, while noncompeting co nstraints play a secondary role in ambiguity resolution. (C) 1998 Acad emic Press.