Forging a morphological system out of two dimensions: Agentivity and number.

Languages have diverse strategies for marking agentivity and number. These strategies are negotiated to create combinatorial systems. We consider the emergence of these strategies by studying features of movement in a young sign language in Nicaragua (NSL). We compare two age cohorts of Nicaraguan signers (NSL1 and NSL2), adult homesigners in Nicaragua (deaf individuals creating a gestural system without linguistic input), signers of American and Italian Sign Languages (ASL and LIS), and hearing individuals asked to gesture silently. We find that all groups use movement axis and repetition to encode agentivity and number, suggesting that these properties are grounded in action experiences common to all participants. We find another feature - unpunctuated repetition - in the sign systems (ASL, LIS, NSL, Homesign) but not in silent gesture. Homesigners and NSL1 signers use the unpunctuated form, but limit its use to No-Agent contexts; NSL2 signers use the form across No-Agent and Agent contexts. A single individual can thus construct a marker for number without benefit of a linguistic community (homesign), but generalizing this form across agentive conditions requires an additional step. This step does not appear to be achieved when a linguistic community is first formed (NSL1), but requires transmission across generations of learners (NSL2).

Watching language grow in the manual modality: nominals, predicates, and handshapes.

All languages, both spoken and signed, make a formal distinction between two types of terms in a proposition--terms that identify what is to be talked about (nominals) and terms that say something about this topic (predicates). Here we explore conditions that could lead to this property by charting its development in a newly emerging language--Nicaraguan Sign Language (NSL). We examine how handshape is used in nominals vs. predicates in three Nicaraguan groups: (1) homesigners who are not part of the Deaf community and use their own gestures, called homesigns, to communicate; (2) NSL cohort 1 signers who fashioned the first stage of NSL; (3) NSL cohort 2 signers who learned NSL from cohort 1. We compare these three groups to a fourth: (4) native signers of American Sign Language (ASL), an established sign language. We focus on handshape in predicates that are part of a productive classifier system in ASL; handshape in these predicates varies systematically across agent vs. no-agent contexts, unlike handshape in the nominals we study, which does not vary across these contexts. We found that all four groups, including homesigners, used handshape differently in nominals vs. predicates--they displayed variability in handshape form across agent vs. no-agent contexts in predicates, but not in nominals. Variability thus differed in predicates and nominals: (1) In predicates, the variability across grammatical contexts (agent vs. no-agent) was systematic in all four groups, suggesting that handshape functioned as a productive morphological marker on predicate signs, even in homesign. This grammatical use of handshape can thus appear in the earliest stages of an emerging language. (2) In nominals, there was no variability across grammatical contexts (agent vs. no-agent), but there was variability within- and across-individuals in the handshape used in the nominal for a particular object. This variability was striking in homesigners (an individual homesigner did not necessarily use the same handshape in every nominal he produced for a particular object), but decreased in the first cohort of NSL and remained relatively constant in the second cohort. Stability in the lexical use of handshape in nominals thus does not seem to emerge unless there is pressure from a peer linguistic community. Taken together, our findings argue that a community of users is essential to arrive at a stable nominal lexicon, but not to establish a productive morphological marker in predicates. Examining the steps a manual communication system takes as it moves toward becoming a fully-fledged language offers a unique window onto factors that have made human language what it is.

Children creating language: how Nicaraguan sign language acquired a spatial grammar.

It has long been postulated that language is not purely learned, but arises from an interaction between environmental exposure and innate abilities. The innate component becomes more evident in rare situations in which the environment is markedly impoverished. The present study investigated the language production of a generation of deaf Nicaraguans who had not been exposed to a developed language. We examined the changing use of early linguistic structures (specifically, spatial modulations) in a sign language that has emerged since the Nicaraguan group first came together: In tinder two decades, sequential cohorts of learners systematized the grammar of this new sign language. We examined whether the systematicity being added to the language stems from children or adults: our results indicate that such changes originate in children aged 10 and younger Thus, sequential cohorts of interacting young children collectively: possess the capacity not only to learn, but also to create, language.

A cross-linguistic examination of the noun-category bias: its existence and specificity in French- and Spanish-speaking preschool-aged children.

Previous research has revealed that English-speaking preschoolers expect that a novel count noun (but not a novel adjective), applied to an individual object, may be extended to other members of the same basic or superordinate level category. However, because the existing literature is based almost exclusively on English-speakers, it is unclear whether this specific expectation is evident in children acquiring languages other than English. The experiments reported here constitute the first cross-linguistic, developmental test of the noun-category linkage. We examined monolingual French- and Spanish-speaking preschool-aged children's superordinate level categorization in a match-to-sample task. Target objects were introduced with (a) novel words presented as count nouns (e.g., "This is a fopin"), (b) novel words presented as adjectives (e.g., "This is a fopish one"), or (c) no novel words. Like English-speakers, French- and Spanish-speakers extended count nouns consistently to other category members. This is consistent with our prediction that the mapping between count nouns and object categories may be a universal phenomenon. However, children's extension of novel adjectives varied across languages. Like English-speakers, French-speakers did not extend novel adjectives to other members of the same category. In contrast, Spanish-speakers did extend novel adjectives, like count nouns, in this fashion. This is consistent with our prediction that the mappings between adjectives and their associated applications vary across languages. The results provide much-needed cross-linguistic support for the noun-category linkage and illustrate the importance of the interplay between constraints within the child and input from the language environment.