Expressing generic concepts with and without a language model. 
Utterances expressing generic kinds ("birds fly") highlight qualities of a category that are stable and enduring, and thus provide insight into conceptual organization.  To explore the role that linguistic input plays in children's production of generic nouns, we observed American and Chinese deaf children whose hearing losses prevented them from learning speech and whose hearing parents had not exposed them to sign.  These children develop gesture systems that have language-like structure at many different levels.  The specific question we addressed in this study was whether the gesture systems, developed without input from a conventional language model, would contain generics.  We found that the deaf children used generics in the gestures they invented, and did so at about the same rate as hearing children growing up in the same cultures and learning English or Mandarin.  Moreover, the deaf children produced more generics for animals than for artifacts, a bias found previously in adult English- and Mandarin-speakers and also found in both groups of hearing children in our current study.  This bias has been hypothesized to reflect the different conceptual organizations underlying animal and artifact categories.  Our results suggest that not only is a language model not necessary for young children to produce generic utterances, but the bias to produce more generics for animals than artifacts also does not require linguistic input to develop.