TLC :: The Human Face is a good article discussing facial beauty and proportions.
“Dr. Marquardt theorizes that we discern whether a face is obviously human by unconsciously comparing it to an ideal face that lurks in the unreachable recesses of the psyche. Since we have no direct access to this ideal “most human” face, we can’t say precisely what it is; however, Dr. Marquardt claims he has captured the ideal face in his beauty mask. He says, “The mask radiates, it advertises and screams: ‘human, human, human.’ “