[FITZ]

There is no language structure, there is only understanding.

Facial expressions are one non-language form of communication. So are other hand-gestures.

[fifteendogs]

True, but these extraneous gyrations are used only to improve the level of understanding of the language being used to communicate. I have never experienced deafness so I am unable to understand how much is communicated in sign language. I have experienced silent communication without the benefit of visual enhancements and was able to completely understand what was being communicated.