D. MacLaughlin & S. McEwen (eds.), Proceedings of the Boston UniversityConference on Language Development 19, 543-552. Boston: Cascadilla Press.1995. © 1994 Ann Senghas.The Development of Nicaraguan Sign Language via theLanguage Acquisition ProcessAnn Senghas, Massachusetts Institute of Technology1. IntroductionOne of the central goals in research on language acquisition is to discoverwhat knowledge and abilities children bring to the learning situation. Neverbefore in the history of language research has there been a better opportunity toask this question as the current situation in Nicaragua, where young childrendeprived of exposure to any language are inventing a new one.Only sixteen years ago, public schools for deaf children were firstestablished in Nicaragua. Despite the fact that these schools advocated an oral,rather than signing, approach to education, they served as a magnet for a newcommunity of deaf children who had not previously had contact with oneanother. Consequently, these children created their own indigenous signlanguage. The language is not a simple code or gesture system; it has alreadyevolved into a full, natural language. It is independent from Spanish, the spokenlanguage of the region, and is unrelated to American Sign Language (ASL), thesign language used in most of North America.The present study examines how this first generation of signers is imposinggrammatical structure on their sign language as it develops. The method whichguides this work is one that is central to language acquisition research: byexamining the structure evident in the children's sign language production, andsubtracting from that the portion present in the language to which the childrenwere originally exposed, one can discover the children's contribution. 2. The development of Nicaraguan Sign LanguageKegl & Iwata (1989) described some of the earliest stages of Nicaraguansigning, comparing it to ASL and evaluating its status as a creole. So far, twodistinct forms of the sign language have emerged. The oldest members of thecommunity, who are now in their mid- to late-twenties, entered the schools in1978, each with a different, highly idiosyncratic homesign or gesture system.Upon contact they developed a now partially-crystallized pidgin called Lenguajede Signos Nicaragüense (LSN) which they continue to use today. Younger deafchildren (many as young as four years old) who entered the deaf community sincethat time were exposed to the pidgin LSN used by the older children. From thisimpoverished language input they produced something richer: the new creoleIdioma de Signos Nicaragüense (ISN). ISN is a full-fledged, primary signlanguage, resulting from the process of nativization, or abrupt creolization asBickerton (1984) defines it.An initial set of acquisition studies has revealed several specific grammaticalstructures that the younger children have developed, including an inflectionalverb morphology system and a noun classifier system. These constructions were544found primarily in the signing of the younger ISN signers, and were much lesscommon in the signing of the older LSN signers (Senghas et al., 1994;Senghas, 1994).3. Age at Entry and Year of EntryThe present study attempts to tease apart the potential sources of thesemorphological changes. In particular, it examines the degree of grammaticalcomplexity with respect to two different factors which are predicted to combineto account for the differences we have noted between older and younger signers.The first is a child’s age at the time of entry into the signing community, orAge at Entry. Children who are exposed to a language at a younger ageultimately achieve greater fluency in the language than those who are exposedonly later in life. This point is clear from common observation, and has beenshown experimentally (Newport, 1990). Because the ages at which deafNicaraguans acquired sign language range from birth to very late adolescence, onecan compare their command of certain constructions to pinpoint the ages atwhich the constructions can be mastered. The effect of Age at Entry likelyaccounts for a portion of the observed differences between LSN and ISN signers,since late-exposed signers are more apt to be in the older LSN group.A second factor which may account for differences in grammaticalcomplexity is a child’s Year of Entry into the signing community, that is,whether the child began learning the sign language at an earlier or later point intime, such as 1981 vs. 1990. If the language is indeed becoming richer overtime, signers who entered the community more recently should have beenexposed to richer signing than signers who entered the community in its earliestyears. More complex signing among children with a later Year of Entry wouldbe evidence that the complexities have appeared in recent years. 4. Current study: narrative elicitation task4.1. ProcedureThe subjects of the present study are 25 deaf Nicaraguan signers whose agesat the time of testing ranged from 7;6 to 31;11, with a mean of 21;1. Their Ageat Entry ranges from birth to 27;5, with a mean of 9;10 and their Year of Entryranges from 1978 to 1990. Each subject was presented with a 2-minute animated cartoon (Mr. KoumalBattles his Conscience, Studio Animovaného Filmu, 1973) and asked to sign thestory to a deaf peer. The narratives were videotaped, and the videotapes were thencoded with respect to what events were represented, and which morphologicaldevices were used in recounting those events. In particular, we examined certainfeatures of the verb phrase: how many arguments a verb can take, specificinflections that can be incorporated into verbs, and whether those inflections areused to mark agreement with other words in the narrative.5454.1.1. Number of arguments per verbOne measure of grammatical complexity is the number of arguments perverb. It is likely that the syntactic structure needed for a verb to support morethan one argument has only recently appeared in Nicaraguan signing. Verbs’subjects and/or objects