When we converse, information is often conveyed in multiple ways. For those using spoken language, we have, besides the vocal tract, nonverbal articulators as well, including eye gaze (Hanna & Brennan 2007), gesture (Kendon 2004), facial expression (Busso & Narayanan 2007), lip pointing (Sherzer 1983), and puffed cheeks (Sherzer 1993). Likewise, for those using a sign language, we have, besides the hands, nonmanual articulators as well, including facial expressions, eye gaze, mouth, and body posture (Baker & Padden 1978). In this short report we investigate how much information can be simultaneously expressed in sign language (by counting ‘propositions’) and conclude that there are limitations. We then consider the nature of these limitations, and finish by briefly comparing the situation in spoken language to the situation in sign languages.
Donna Jo Napoli and R. Sutton-Spence.
"Limitations On Simultaneity In Sign Language".