Verb Agreement as a Linguistic Innovation in Signed Languages

This chapter focuses on the set of verbs that describe an event involving at least two participants. It proposes that these verbs undergo a linguistic innovation, which adds the ability to interact with gesture to result in a new linguistic form. This particular linguistic innovation involves verb agreement, an encoding of the relationship between the verb and its arguments via the arguments' morphosyntactic features. This proposal is supported on the basis of the internal structure and the development of the verbs in documented sign languages. First, the verbs share three properties in common: they select for two animate arguments, they express the morphological features of person and number, and they undergo a phonological change in orientation and/or direction of movement. These properties place these verbs in complementary distribution with spatial and plain verbs. Second, the extent of cross-linguistic variation with respect to word order and with respect to the use of auxiliaries reveals grammatical constraints on possible behaviors for verbs participating in agreement. Third, developmental studies of argument structure and person show that these properties must be learned correctly, suggesting they belong to a linguistic system. These arguments taken together make the case that these verbs participate in a grammatical process. Historical studies show that this grammatical process has emerged through interaction with deictic gesture which remains ongoing. Thus verb agreement as part of a linguistic innovation is distinct from other cases of grammaticization which can be rooted in gesture but are completely disassociated from it in the end. To date, the paper covers the most comprehensive and critical review and analysis on grammatical properties in verb agreement, development of verb agreement and interaction between verb agreement and gestures in the literature on sign linguistics.