My main research program centers on the semantics of "generic" sentences—sentences expressing generalizations such as "Birds fly". This topic includes not only how to represent their meanings in a formal system in some general way, but other questions that bear on this overall task. One offshoot concerns the syntax and semantics of determinerless noun phrases, including bare plurals and mass terms, as well as the "generic" readings of such expressions as "the tiger" or "a student". I am most interested in the idea that that determinerless NP's make direct reference to kinds. Another outgrowth of this work concerns cross-linguistic verbal and nominal morphology, since languages have different formal means of expressing genericity, which can give us vital clues to how to represent their meanings in general, and clues to the place they might occupy in AI knowledge representation (in this I collaborate with Lenhart Schubert of computer science).
Still another area of investigation concerns the proper treatment of the "Stage-level/Individual-level" distinction among natural language predicates. The study of the character of generics has also caused me to consider their functioning in discourse and hence into the areas of tense and aspect, which in turn interact strongly with genericity. The study of generics brings up philosophical issues as well, such as the problem of induction, the character of dispositions, the question of the existence of events, the nature of sortals, etc., and in this I have benefited from a longstanding collaboration with F. J. Pelletier, currently at Simon Fraser University. I also have interests stemming from work on event semantics concerning the nature of "thematic roles" associated with verb meanings. The problem with "thematic roles" is that their linguistic status is uncertain in that formal indications of roles are very weak and do not allow us to easily enumerate and individuate roles. Nevertheless, they are useful and insightful constructs. Not quite so closely related to the study of generics is an interest and contributions to the question of how to represent "free-choice" any in a formal semantics, the nature of the adjectives same and different, and a type of relative clause construction commonly called "amount relatives".
My final area of research, in psycholinguistics, is carried out entirely collaboratively. My work in psycholinguistics began in graduate school (on language acquisition), and then transformed into a long-standing collaboration with psycholinguist Michael K. Tanenhaus and many graduate students and postdoctoral fellows, centering on the character of sentence processing. Recently it has begun to change into work on semantic and pragmatic processing. One focus of the experimental work has been on lexical structure, and the question of what information is accessed in processing upon recognizing a word, whether in print or when spoken. Some of this has concerned thematic roles, but also this has gotten into other aspects of argument structure and lexical meanings. This line of work has also taken in the question of the representation of "deletion" phenomena, including Verb Phrase deletion in English, and the character of "deleted" Noun Phrases. One aspect of this work has also considered experimental techniques for examining discourse structures, and the organization of information used in forming a discourse. Beyond these main research agendas, I have over the years made occasional contributions to natural language syntax and morphology, language acquisition, and the nature of the field of linguistics.