Discriminant Features and Temporal Structure of Nonmanuals in American Sign Language
In A we show a neutral face. A neutral face is defined as one without expression where all facial muscles are relaxed (except for the eyelids which are open). B We consider two configural positions for the eyebrows (up and down). C Blinks are marked by closing the eyelids. D The mouth can be open or closed. E We also annotate mouth shape where appropriate (flat, round and other). F When there is teeth showing, we consider three distinct positions – closed (top and bottom teeth touching), open (not touching), touching lips (where the top teeth are over the lower lip or the bottom teeth touch the upper lip). G–I We also consider the three possible rotations of the head – turns, tilts and forward/backward movements.