Are both sign language and gestures best defined in terms of what they should look like?

Reading in Crasborn‘s (2001) thesis always gives me plenty to think about. One thing struck me yesterday. The emphasis placed on perception in the modeling of sign language. I read the same before in a review by Sara Fortuna of ‘Ideeen zu Einer Mimik’ and other works of Johann Jakob Engel. Crasborn describes sign language (NGT) and Engel describes gestures mostly in a theatrical context. One is about signers and their conversational partners, the other about actors and their audience. Yet they both state that a gesture (or sign) is defined in terms of what it should look like.

Is a perfect sign in the eye of the beholder? (source Heather Brooks)
What a gesture should look like is the code shared between producer and observer. It is the language, or the semiotic system, employed by them. We articulate a gesture in such a way that it will hopefully carry the right message. We try to produce something that looks like the target. When we do this we take into account both how we think the observer sees it, but we may also reflect on our production ourselves.

Wait a minute. I might be writing trivial stuff here. Is not the same statement about production for perception true for almost anything? Do we all try to be the perfect wife or husband, or do we try to look like it? And when my daughter of 4 is told to clean up, I think she is trying very hard to look busy, while minimizing actual effort.

Do we act to look like we should? (source)

My mentor Ans said we all carry part of the world inside us just as much as we are part of the world. We adjust our behaviour for others. Gestures are no exception. And so, the importance of perception is nothing special for gestures.

In comparison with studies of production it is an empty statement to say perception is more important. True, without an underlying perceptual specification there can be no efficient communication. But we may get to a shared code only after many tried productions. And without production there is nothing to perceive. I may think I know exactly what a tree falling in the woods should sound like, but without an actual tree falling, can there be a debate?