Complementizer agreement is clitic doubling

Complementizer agreement in minority and nonstandard West Germanic languages is well-known and frequently studied, but there is little agreement on its analysis. In this paper, I add to this debate by presenting novel and underdiscussed data from Frisian and Limburgian on intervention effects: what happens to complementizer agreement when the complementizer and the subject are separated by an intervening element. In Frisian, intervention leads to ungrammaticality, and in Limburgian, it leads to the realization of complementizer agreement between the intervener and the subject. These effects cannot be accounted for by existing Agree and PF analyses of complementizer agreement. Instead, I argue that the complementizer agreement morpheme is a clitic. Adopting the approach to clitic doubling of van Craenenbroeck and van Koppen (2008), I develop an analysis of complementizer agreement as clitic doubling. The intervention effects in Frisian and Limburgian follow from an interplay of the structural size of the clitic and restrictions on movement. Specifically, the ungrammaticality of intervention in Frisian is the result of competition between the clitic and the intervener for the same structural position, and the subject-internal realization of complementizer agreement in Limburgian is the result of movement of the clitic below the intervener.