The communicative importance of agent-backgrounding: Evidence from homesign and Nicaraguan Sign Language

Validating Silent Gesture Lab Studies in a Naturally Emerging Sign Language: How Order is Used to Describe Intensional Versus Extensional Events in Nicaraguan Sign Language

Languages are neither designed in classrooms nor drawn from dictionaries-they are products of human minds and human interactions. However, it is challenging to understand how structure grows in these circumstances because generations of use and transmission shape and reshape the structure of the languages themselves. Laboratory studies on language emergence investigate the origins of language structure by requiring participants, prevented from using their own natural language(s), to create a novel communication system and then transmit it to others. Because the participants in these lab studies are already speakers of a language, it is easy to question the relevance of lab-based findings to the creation of natural language systems. Here, we take the findings from a lab-based language emergence paradigm and test whether the same pattern is also found in a new natural language: Nicaraguan Sign Language. We find evidence that signers of Nicaraguan Sign Language may show the same biases seen in lab-based language emergence studies: (1) they appear to condition word order based on the semantic dimension of intensionality and extensionality, and (2) they adjust this conditioning to satisfy language-internal order constraints. Our study adds to the small, but growing literature testing the relevance of lab-based studies to natural language birth, and provides convincing evidence that the biases seen in the lab play a role in shaping a brand new language.

Visual Form and Event Semantics Predict Transitivity in Silent Gestures: Evidence for Compositionality

Silent gesture is not considered to be linguistic, on par with spoken and sign languages. It is claimed that silent gestures, unlike language, represent events holistically, without compositional structure. However, recent research has demonstrated that gesturers use consistent strategies when representing objects and events, and that there are behavioral and clinically relevant limits on what form a gesture may take to effect a particular meaning. This systematicity challenges a holistic interpretation of silent gesture, which predicts that there should be no stable form-meaning correspondence across event representations. Here, we demonstrate to the contrary that untrained gesturers systematically manipulate the form of their gestures when representing events with and without a theme (e.g., Someone popped the balloon vs. Someone walked), that is, transitive and intransitive events. We elicited silent gestures and annotated them for manual features active in coding transitivity distinctions in sign languages. We trained linear support vector machines to make item-by-item transitivity predictions based on these features. Prediction accuracy was good across the entire dataset, thus demonstrating that systematicity in silent gesture can be explained with recourse to subunits. We argue that handshape features are constructs co-opted from cognitive systems subserving manual action production and comprehension for communicative purposes, which may integrate into the linguistic system of emerging sign languages. We further suggest that nonsigners tend to map event participants to each hand, a strategy found across genetically and geographically distinct sign languages, suggesting the strategy's cognitive foundation.

Universal Constraints on Linguistic Event Categories: A Cross-Cultural Study of Child Homesign

Languages carve up conceptual space in varying ways-for example, English uses the verb cut both for cutting with a knife and for cutting with scissors, but other languages use distinct verbs for these events. We asked whether, despite this variability, there are universal constraints on how languages categorize events involving tools (e.g., knife-cutting). We analyzed descriptions of tool events from two groups: (a) 43 hearing adult speakers of English, Spanish, and Chinese and (b) 10 deaf child homesigners ages 3 to 11 (each of whom has created a gestural language without input from a conventional language model) in five different countries (Guatemala, Nicaragua, United States, Taiwan, Turkey). We found alignment across these two groups-events that elicited tool-prominent language among the spoken-language users also elicited tool-prominent language among the homesigners. These results suggest ways of conceptualizing tool events that are so prominent as to constitute a universal constraint on how events are categorized in language.

Structural biases that children bring to language learning: A cross-cultural look at gestural input to homesign

Linguistic input has an immediate effect on child language, making it difficult to discern whatever biases children may bring to language-learning. To discover these biases, we turn to deaf children who cannot acquire spoken language and are not exposed to sign language. These children nevertheless produce gestures, called homesigns, which have structural properties found in natural language. We ask whether these properties can be traced to gestures produced by hearing speakers in Nicaragua, a gesture-rich culture, and in the USA, a culture where speakers rarely gesture without speech. We studied 7 homesigning children and hearing family members in Nicaragua, and 4 in the USA. As expected, family members produced more gestures without speech, and longer gesture strings, in Nicaragua than in the USA. However, in both cultures, homesigners displayed more structural complexity than family members, and there was no correlation between individual homesigners and family members with respect to structural complexity. The findings replicate previous work showing that the gestures hearing speakers produce do not offer a model for the structural aspects of homesign, thus suggesting that children bring biases to construct, or learn, these properties to language-learning. The study also goes beyond the current literature in three ways. First, it extends homesign findings to Nicaragua, where homesigners received a richer gestural model than USA homesigners. Moreover, the relatively large numbers of gestures in Nicaragua made it possible to take advantage of more sophisticated statistical techniques than were used in the original homesign studies. Second, the study extends the discovery of complex noun phrases to Nicaraguan homesign. The almost complete absence of complex noun phrases in the hearing family members of both cultures provides the most convincing evidence to date that homesigners, and not their hearing family members, are the ones who introduce structural properties into homesign. Finally, by extending the homesign phenomenon to Nicaragua, the study offers insight into the gestural precursors of an emerging sign language. The findings shed light on the types of structures that an individual can introduce into communication before that communication is shared within a community of users, and thus sheds light on the roots of linguistic structure.