Mothers Do Not Drive Structure in Adult Homesign Systems: Evidence from Comprehension

Mothers Do Not Drive Structure in Adult Homesign Systems: Evidence from Comprehension Emily M. Carrigan (emily.carrigan@uconn.edu) Department of Psychology, 406 Babbidge Road Storrs, CT 06269-1020 USA Marie Coppola (marie.coppola@uconn.edu) Department of Psychology, 406 Babbidge Road Storrs, CT 06269-1020 USA Department of Linguistics, 337 Mansfield Road Storrs, CT 06269-1145 USA Abstract Some profoundly deaf individuals without conventional linguistic input develop gestures, called “homesign,” to communicate. We examined homesign systems (HSs) used by four deaf Nicaraguan adults (ages 15-27), and evaluated whether homesigners’ mothers are potential sources for these systems. Study One measured mothers’ comprehension of descriptions of events (e.g., “A man taps a woman”) produced in homesign and spoken Spanish. Mothers comprehended spoken Spanish descriptions (produced by a hearing child) better than homesign descriptions, suggesting a greater degree of sharedness for spoken Spanish. Study Two compared the homesign comprehension of each homesigner’s mother to that of a native user of American Sign Language (ASL). ASL Signers performed better than mothers, confirming that homesign productions contain comprehensible information, to which mothers are not fully sensitive. Taken together, these results suggest that mothers are not the source of their deaf child’s HS, and add to evidence that HSs are more like language than like gesture. Keywords: Language acquisition; homesign; deafness; language creation; gesture; sign language; Nicaragua Introduction 2003). The gestures and gesture combinations produced by the mothers of child homesigners lack the morphological and syntactic structure observed in the children’s productions (e.g., Goldin-Meadow & Mylander 1984, 1990; Goldin- Meadow et al. 1994, Goldin-Meadow 2003). While mothers’ gestures may serve as an initial foundation for their deaf child’s homesign system, children surpass whatever “input” they might receive from their mother. These mothers tended not to engage in gestural communication with the child homesigners, and such child homesigns are used for a relatively short time, until the children reach school age. It is possible that, given increased gestural communication and a lengthier period of use, mothers might play a greater role in the development of homesign systems. This research examines homesign systems developed with communication partners who engage homesigners using gesture, unlike the young deaf children studied by Goldin- Meadow and her colleagues. In Nicaragua, we can locate rare cases in which deaf individuals develop and use homesign systems as their primary means of communication for their entire lives. These individuals are not part of the Deaf community that uses the recently emerged Nicaraguan Sign Language (NSL) (Senghas, 1995; Senghas & Coppola, 2001). The homesigners do not learn conventional sign language, and they have not acquired the Spanish spoken around them. These mature homesign systems display many linguistic features, for instance, the grammatical relation of Subject (Coppola & Newport, 2005), proto-pronouns (Coppola & Senghas, 2010), use of space, and devices for establishing reference (Coppola & So, 2005). Given the accumulated interactions over time between a homesigner and his or her family members, and the more abstract, language-like devices that homesigners produce, it is possible that these family members may have contributed more to the development of the homesign system than the mothers of the homesigners Goldin-Meadow & colleagues observed. One step in determining the source of the linguistic features we observe in mature homesign is evaluating family members’ potential contributions. The language sciences have long grappled with the question of what drives language acquisition. At the heart of this debate is the question: What are the contributions of language input versus the contributions of the learner? It can be difficult to disentangle these two factors in typical language acquisition situations, as such situations do not offer the opportunity to experimentally manipulate the presence of linguistic input. Studying spontaneously occurring cases of degraded linguistic input can help discern human predispositions for language learning. Previous research has shown that children can surpass their linguistic input (e.g., Singleton & Newport, 2004, Senghas & Coppola, 2001). In addition, some deaf children born into hearing families have no access to signed or spoken linguistic input. While their parents primarily speak, and do not use gesture with them, these children nevertheless use a system of manual gestures, called “homesign,” to communicate. Homesign has many, but not Study One all, of the features of fully developed languages (e.g., a stable lexicon, basic syntax and morphology, Goldin-Meadow, We begin by evaluating homesigners’ mothers as potential sources, because they each have significant gestural