In Chapter 6, McMurphy tells Chief Bromden that a black orderly is coming, and Chief immediately gets into bed. Later, McMurphy tells Chief that he saw him jump when he told Chief this information, so McMurphy knows that Chief is not deaf.

However, McMurphy and Chief do not speak until chapter 24. Chief feels like he wants to tell McMurphy that he would like to go on the fishing trip that McMurphy is organizing. However, Chief can't speak to McMurphy because Chief has long acted deaf and unable to speak. One night, McMurphy tries to get Chief to laugh by asking him if his gum loses its flavor when it's been stuck to the bedpost. Then, McMurphy gives Chief a stick of gum, and Chief tells him thank you. Chief's voice is rusty from not having used it for so long. Chief then gets into a long conversation with McMurphy. McMurphy senses from the beginning of their acquaintance that Chief is not deaf or mute, and he eventually draws Chief out of his shell.

McMurphy discovers that Chief Bromden is not deaf when he is assigned a bed next to the Bromden. One night when McMurphy climbs into bed, he warns Bromden that one of the orderlies is coming to douse the lights. Bromden is startled when McMurphy says this.

After the snickering orderly ties the sheets on Bromden, he departs, and Bromden hears McMurphy next to him breathing deeply as the covers on him rise and fall. Soon, however, McMurphy begins a "soft, throaty sound" that develops into a low chuckle. Turning toward Bromden, he whispers happily,

"Why, you sure did give a jump when I told you that coon was coming, Chief. I thought somebody told me you was deef."

Despite learning Bromden's secret, McMurphy does not reveal the truth to anyone; he only talks to Bromden when no one else is around. For, Bromden pretends to be deaf because the orderlies will speak their "hate secrets" aloud before him. He also witnesses the hatred that Nurse Ratched has for these men in some of her responses to them, as well as her actions. Of course, McMurphy realizes that Bromden's opportunities to see and hear the real interaction that transpires with the orderlies and with Nurse Ratched may someday prove useful to him.