One flew over the Cuckoo's nest- laughter as a symbol

Throughout the book, One Flew Over the Cuckoo’s Nest, laughter is used as a proof of sanity as well as a means of weaponry against Big Nurse. It is the ultimate form of self-expression. True laughter is rarely shown by characters. Each incident laughter is found in the ward is an important symbol and occurrence in the novel.
The first time Ken Kesey introduces the audience to laughter is coincidentally with the introduction of Randall Patrick McMurphy. All characters (patients and staff) are dumbfounded and don’t know what to do when they hear his laughter. Bromden notes that it’s “real” and the first actual laughter he has heard in years. To make sure audiences understand laughter as the important symbol it is Ken Kesey even elaborates on it’s introduction to the ward:

He laughs till he’s finished for a time, and he walks on into the day room. Even when he isn’t laughing, that laughing sound hovers around him, the way the sound hovers around a big bell j...