The organization of verb meaning in Lengua de Señas Nicaragüense (LSN): Sequential or simultaneous structures?

One structural dimension that varies across languages is the simultaneous or sequential expression of meaning. Complex predicates can layer meanings together simultaneously in a single-verb predicate (SVP) or distribute them sequentially in a multiple-verb predicate (MVP). We ask whether typological variability in this dimension might be a consequence of systematic patterns of diachronic change. We examine the distribution of markers of agency and number within the verb phrase (the predicate) in the earliest stages of a young, emerging sign language in Nicaragua, Lengua de Señas Nicaragüense (LSN), beginning with homesign systems like those from which LSN originated, and progressing through two decades of transmission to new learners. We find that: (i) LSN2 signers are more likely to produce MVPs than homesigners or LSN1 signers; (ii) in the MVPs they do produce, homesigners and LSN1 signers are more likely to produce predicates that mark both agency and number simultaneously on at least one of the verbs; LSN2 signers are just as likely to produce sequences with verbs that mark agency and number in sequentially separate verbs. We discuss how language acquisition, modality, and structure, as well as specific social factors associated with each of the groups, play a role in driving these changes, and how, over time, these patterns of change might yield the diversity of forms observed across spoken and signed languages today.