My main field of study is syntax. My work aims to further our understanding of the limits of syntactic variation by comparing languages that differ minimally from one another.

My research aims to make new empirical generalizations and use them to test and refine the current theory. It bears in particular on the following notions and domains:

Micro-syntactic variation

I started out working on micro-syntactic differences among varieties of Romance, focusing on sentential negation. More recently I have extended my domain of investigation to minimal differences in the morpho-syntactic properties of varieties of English spoken in North America. I began pursuing this interest about ten years ago,  focusing on Appalachian English in collaboration with Judy Bernstein, Marcel den Dikken and Christina Tortora. In 2011, I founded the Yale Grammatical Diversity Project, a research group that aims to document and study grammatical diversity in North American English more broadly.  We ask questions such as the following: Which aspects of the grammar of English exhibit syntactic variation? In which geographical areas is such syntactic variation attested (in the cases in which it is defined geographically)? What does such variation tell us about the grammatical architecture of English, and of human language more generally? 

The notion of clause type

I have worked extensively on the notion of clause type, mostly in collaboration with Paul Portner (Georgetown). Our joint work began as an attempt to give precise theoretical content to notions that are commonly used by linguists, and yet still escape a precise characterization – for example, what makes a clause a declarative, interrogative, exclamative, or imperative. We published a number of papers on the syntax and semantics of exclamatives. It was funded by a two-year NSF grant ("Clause Types: Form and Force in Grammatical Theory", BCS-0234278) and led to a number of presentations and publications. Working with the small research group that the grant allowed us to create has been one of the most rewarding experiences of my academic life.

Sentential negation

In my earlier work, I have investigated in depth the syntactic representation of sentential negation. I have examined Romance varieties, carrying out a detailed comparison of varieties that include not only the more widely spoken and well studied languages (like Italian and French), but also several varieties that are spoken in small communities and have not yet been extensively investigated (the so- called "dialects" of Northern Italy and Southern France). By comparing minimally different varieties, it is possible to construct sentences that are the same in all respects, except for the expression of sentential negation. This has allowed me to conduct an in-depth investigation of the structural position of the markers of sentential negation, and to examine the effect that their position has on other aspects of grammar. This work has led to several publications, including my 1997 book with Oxford University Press, Negation and Clausal Structure: A Comparative Study of Romance Languages.