The doctor's behavior in this scene is interesting in that it closely resembles the work of a psychoanalyst, but precedes the "father of psychoanalysis," Freud, by centuries. Like a Freudian psychoanalyst, the doctor observes Lady Macbeth's dreams and uses her words to infer the cause of her distress. Like a psychoanalyst, too, the doctor decides to "set down what comes from her" as he listens (V.i 34-35). After witnessing her distress, the doctor declares it the result of an "infected mind" (V.i 76); this too sounds like the diagnosis of a modern-day psychiatrist.
Lady Macbeth's language in this scene betrays her troubled mind in many ways. Her speech in previous acts has been eloquent and smooth, for example:
All our service,
In every point twice done and then done double,
Were poor and single business to contend
Against those honors deep and broad wherewith
Your Majesty loads our house. For those of old,
And the late dignities heaped upon them,
We rest your hermits (I.vi 18-24).
In this speech, Lady Macbeth makes use of metaphor (Duncan's honor is "deep and broad"), metonymy (he honors "our house," meaning the Macbeths themselves), and hyperbole ("in every point twice done and then done double"). Her syntax is complex, and the rhythm of her speech is smooth and flowing, in the iambic pentameter used by members of the nobility in Shakespeare's plays. What a contrast it is, therefore, when she speaks in her sleep in act five:
Out, damned spot, out, I say! One. Two. Why then, Œtis time to do't. Hell is murky. Fie, my lord, fie, a soldier and afeard? What need we fear who knows it, when none can call our power to account? Yet who would have thought the old man to have had so much blood in him? . . . . The Thane of Fife had a wife. Where is she now? What, will these hands ne'er be clean? No more o' that, my lord, no more o' that. You mar all with this starting (V.i 36-47).
In this speech, Lady Macbeth's language is choppy, jumping from idea to idea as her state of mind changes. Her sentences are short and unpolished, reflecting a mind too disturbed to speak eloquently. Although she spoke in iambic pentameter before, now she speaks in prose she has lost that noble distance with which she spoke before.
Lady Macbeth's dissolution is swift. This sleepwalking scene is the last time we see her, and a few scenes later, Macbeth receives news that she has died. As Macbeth's power has grown, Lady Macbeth's has decreased. She begins as a remorseless, influential voice capable sweet-talking Duncan and of leading Macbeth to do her bidding. In the third act Macbeth leaves her out of his plans to kill Banquo, refusing to tell her what he intends to do. Now in act five she has dwindled to a mumbling sleepwalker, capable of only the rambling speech of the insane. Whereas event the relatively unimportant Lady Macduff has a stirring death scene, Lady Macbeth dies offstage, and when her death is reported to Macbeth his cold response is shocking in its lack of interest. Here again Macbeth stands in relief to Macduff, whose emotional reaction to his wife's death almost "unmans" him.
