Morpheme structure constraints on two-handed signs in American Sign Language

In ASL, two-handed signs fall into three major sets. In one set the hands have different shapes and either only the dominant hand moves or the hands move as a unit. Battison’s Dominance Condition was intended to account for the fact that the non-dominant hand typically assumes an unmarked shape when it is stationary. However, we show that the non-dominant hand does this even when the hands move as a unit. In the second set the hands have the same shape and only the dominant hand moves. These signs are unrestricted for handshape. In the third set the hands have the same shape and both move. Battison’s Symmetry Condition was intended to account for restrictions on the parameters of these signs. We argue that four basic types of symmetry transformations occur, with various complications: reflection, rotation, translation, and glide reflection, all of which call for conditions specific to them, and lead to an overriding condition on movement in symmetry transformation signs. The conditions uncovered here might be morpheme structure constraints or, instead, simply follow from physiological limitations of hands in motion.