Mary Grace's Human Development book is a psychology textbook often used in college psychology classes. O'Connor's use of it in the story is ironic because Mary Grace, who apparently suffers from some emotional instability to say the least, is the only one who reacts to the hypocrisy and prejudice demonstrated by Mrs. Turpin. This girl's emotional problems allow her to act out in a way her calm, reserved mother, who hears the same remarks Mary Grace does, never would.
Mary Grace must be an intelligent student, for she attends a prestigious women's college. She harbors a great deal of anger for reasons that are only suggested by her mother's references to her daughter's lack of appreciation for what she has. A psychology text could perhaps have instructed her in ways to deal with anger, but clearly she has no control because she attacks Mrs. Turpin violently.
It's ironic that she assaults Ruby who, although puzzled by the girl's strange looks and odd faces at her, is completely unprepared. Psychologically, Mrs. Turpin then must wrestle with the question of whether she really is "a warthog from Hell." Mary Grace is the conduit O'Connor uses to afford Mrs. Turpin her "moment of grace."
Mary Grace is an excellent use of a female Christ figure in literature. Although her name alludes to the Catholic prayer "hail Mary, full of grace" yet her sedate mother is more conforming to the picture of Mary in Catholic thought. Mary Grace has foreknowlege of Mrs. Turpin. "She was looking at her as if she had known and disliked her all of her life--all of Mrs. Turpin's life. Mary Grace is blemished by acne. The story says that she was "blue with acne." In this story the color blue is the symbol of sin. Claude has it and the little boy has it but Ruby doesn't have it until Mary Grace hits her with the book. Isaiah 53:4 says about Christ “there was no beauty that we should desire Him. In theological terms, Ruby was struck down and convicted as a sinner by the book of the law which convicts men of sin before it offers grace. The book is entitled Human Development although Mrs. Turpin is underdeveloped. Mary Grace growls at Ruby every time she has a judgmental thought. The doctor administered the syringe that has the effect of putting Mary Grace to a type of death like Christ. Then the doctor tells us in funeral like terms, "I'll call and make the arrangements," language we use only for funerals. There are many other parallels to explore in the story but the Christ imagery is very strong.