Human natural languages (ie: languages that children can learn without needing to be explicitly taught) are roughly divided into two kinds: oral and gestural. For the most part, hearing people rely on oral language, and deaf people rely on gestural language (unless they were forced to do otherwise as children). There are great similarities in the grammatical underpinnings of oral and gestural natural languages. In fact the two modalities are complementary, particularly during early years of language development, as has been shown by many researchers, including Susan Goldin-Meadow and David McNeill. Structurally the similarities are greater than the differences.
It is interesting to ponder whether it might be possible to combine the best of each. Suppose you and I had a face to face conversation that made use of a well structured combination of oral speech and hand gestures, to create a form of person-to-person verbal communication richer and more detailed in meaning than is achievable through oral communication alone.
Just describing such a scenario raises so many questions. For example, does the scenario even make sense? Would the brain be able to make effective use of an entire complementary channel of communication, above and beyond the sort of language processing that most people employ now? What sorts of things would this extra channel be used for? Even if we knew that, would such a skill be learnable by most people?
I am starting to think about how one might design simple experiments to take steps in this direction. Perhaps people could be asked to describe certain scenarios that are not readily described with verbal speech alone, but that become much easier to described when enhanced by a complementary grammar of hand gestures.
Does anyone know whether questions or experiments like this have been explored before?