Speakers sometimes express information in gestures that they do not express in speech. In this research, we developed a system that could be used to assess the redundancy of gesture and speech in a narrative task. We then applied this system to examine whether children and adults produce non-redundant gesture-speech combinations at similar rates. The coding system was developed based on a sample of 30 children. A crucial feature of the system is that gesture meanings can be assessed based on form alone; thus, the meanings speakers express in gesture and speech can be assessed independently and compared. We then collected narrative data from a new sample of 17 children (ages 5-10), as well as a sample of 20 adults, and we determined the average proportion of non-redundant gesture-speech combinations produced by individuals in each group. Children produced more non-redundant gesture-speech combinations than adults, both at the clause level and at the word level. These findings suggest that gesture-speech integration is not constant over the life span, but instead appears to change with development.

All established languages, spoken or signed, make a distinction between nouns and verbs. Even a young sign language emerging within a family of deaf individuals has been found to mark the noun-verb distinction, and to use handshape type to do so. Here we ask whether handshape type is used to mark the noun-verb distinction in a gesture system invented by a deaf child who does not have access to a usable model of either spoken or signed language. The child produces homesigns that have linguistic structure, but receives from his hearing parents co-speech gestures that are structured differently from his own gestures. Thus, unlike users of established and emerging languages, the homesigner is a producer of his system but does not receive it from others. Nevertheless, we found that the child used handshape type to mark the distinction between nouns and verbs at the early stages of development. The noun-verb distinction is thus so fundamental to language that it can arise in a homesign system not shared with others. We also found that the child abandoned handshape type as a device for distinguishing nouns from verbs at just the moment when he developed a combinatorial system of handshape and motion components that marked the distinction. The way the noun-verb distinction is marked thus depends on the full array of linguistic devices available within the system.