Sign has become a scientific hot button.Only in the past 20 years have specialists in language study realized that signed languages are unique－a speech of the hand.They offer a new way to explore how the brain generates(产生)and understands language，and throw new light on an old scientific debate：whether language，complete with grammar，is something that we are born with，or whether it is a learned behavior.The current interest in sign language has roots in the pioneering work of one teacher at Gallaudet University in Washington，D.C.，world's only liberal arts university for deaf people.