The tone of the novel is despairing and flat at first, but it quickly turns more optimistic once McMurphy arrives and shakes up life in the hospital. One example of Bromden's newfound yet cautious optimism occurs in Part Three, after the fishing trip:
I noticed vaguely that I was getting so’s I could see some good in the life around me. McMurphy was teaching me. I was feeling better than I’d remembered feeling since I was a kid, when everything was good and the land was still singing kids’ poetry to me.
When the novel started, Bromden emphasized that he had been on the ward for 10 years. He described his mundane routine, his dissociative bouts of fog, and his deep suspicion that anyone would ever treat him with dignity. Now, he is noticing "some good in the life around me." The way he remembers his childhood happiness reveals that he is no longer thinking about the mental hospital as the entire, static story of his life. Instead, it is a chapter in a life that has other chapters as well. The idea that McMurphy is "teaching" Bromden suggests that Bromden feels himself learning. Learning is inherently connected with development and the idea that we can become different versions of ourselves in the future. For Bromden, who has been stuck in the hospital longer than any other patient, the sense that he might be able to change and grow constitutes enormous character development.
Bromden's tone tends to be both more optimistic and more lucid when he sees, experiences, or imagines his life outside of the mental hospital. Although the novel ends on the tragic note of McMurphy's lobotomy and death, the tone remains optimistic. This is largely because McMurphy succeeds at helping Bromden and many other patients take charge of their own fates. The illicit nighttime party is joyous because everyone is planning their exit from the hospital that has kept them from living their lives. Even after McMurphy loses his own fight, Bromden's tone remains cautiously optimistic. At last, he is not afraid to interact with the other patients, to take a stand, and to leave the hospital on his own.