Each of the three members of the Sawyer family had a near debilitating mental illness. Leatherface was retarded (probably among other things), the Hitchhiker was probably schizophrenic (Ed Neal, the actor who played him, modeled the character on a cousin of his who suffered from schizophrenia) and Drayton...well, Drayton always struck me as having some type of split personality disorder. One minute he was apologetic and somewhat sympathetic to Sally’s plight (“No need to torture the poor girl!”) and the next he gleefully mocked her and laughed as Grandpa hit her with a hammer. In fact, you can see him transitioning from one personality to the other.