As Bromden's fog clears over the course of the novel, he begins to have flashbacks to his childhood and the events that led to his difficulties with mental health. One example of this motif occurs in Part Three, when he thinks about when he first started letting others believe he was deaf:
Lying there in bed, I tried to think back when I first noticed it. I think it was once when we were still living in the village on the Columbia. It was summer....
... and I’m about ten years old and I’m out in front of the shack sprinkling salt on salmon for the racks behind the house, when I see a car turn off the highway and come lumbering across the ruts through the sage, towing a load of red dust behind it as solid as a string of boxcars.
The ellipses at the end of one paragraph and the beginning of the next help denote for the reader that the narration is skipping backward in time and to a different place. However, Bromden continues to use present tense verbs. In his mind, he really is back on the Columbia River at 10 years old, watching a car stir up the dust in the sage. Bromden goes on to describe the conversation the people in the car had right in front of him. They discussed their plan to dam up the river, the source of the salmon Bromden was salting at the time. They ultimately decided not to inform Bromden's father of their plan at that time, even though they knew it would entirely disrupt his life: they did not want to give him the chance to disrupt their dam project. In the flashback, Bromden hears the entire conversation and says nothing. He understands himself to be part of the background for these adults; they don't think of him as another person who understands them and might respond. In fact, they hardly notice him at all.
By filling in Bromden's past through flashbacks, Kesey highlights the impact of memory and trauma on his narrator's life in the present. He also highlights Bromden's complex humanity. Bromden is not only an adult man living on a psychiatric ward. He is also a 10-year-old boy listening to blasé conversations about the destruction of his home. He is also a soldier in World War II. He is also a boy somewhat older witnessing his father's grief and anger drive him deep into alcoholism. The flashbacks help make Bromden's "craziness" make complete sense, so that the reader begins to see him not as someone to be cordoned off from society, but rather as someone society has forced into exile.
In Part Four, when Bromden is subjected to electroshock therapy, his narration is overtaken by flashbacks that he experiences as a stream of consciousness:
The machine hunches on me.
AIR RAID.
Hit at a lope, running already down the slope. Can’t get back, can’t go ahead, look down the barrel an’ you dead dead dead.
We come up outa the bullreeds run beside the railroad track. I lay an ear to the track, and it burns my cheek.
“Nothin’ either way,” I say, “a hundred miles....”
“Hump,” Papa says.
“Didn’t we used to listen for buffalo by stickin’ a knife in the ground, catch the handle in our teeth, hear a herd way off?”
The machine "hunching" on Bromden is the machine that is going to shock him. Either as soon as the shock comes or in anticipation of it, Bromden flashes on a traumatic experience he had in World War II. During the war, he and other soldiers were trained to run as fast as they could without looking back when they heard the siren that indicated an air raid, or bombing. Suddenly, in his head, Bromden is not pinned down receiving shock treatment but is instead running away from bombs. The way the coming shock reminds him of the air raids underscores how terrifying EST is for Bromden and the other patients. It feels like being bombed. At the same time, the memory of running from an air raid serves as a kind of escapist fantasy: at least when the bombs came down he had the freedom to run. Now, he can't go anywhere except into his own mind to get away from the shock.
The flashback is not entirely coherent, however. Bromden's mind glides smoothly from the air raid to a hunting trip with his father. It is not clear exactly when the scene changes. Perhaps it is when "[w]e come up outa the bullreeds," but "we" could refer to either Bromden and his father or Bromden and his fellow soldiers. Only when "Papa" speaks is it clear to the reader that Bromden has switched to a different scene than he started with. This kind of indistinct, dreamlike transition between scenes is characteristic of stream-of-consciousness writing. Kesey uses it to demonstrate how Bromden's fear plunges him into free association. Essentially, Bromden's life is flashing before his eyes in a way that does not make narrative sense but that makes perfect emotional sense.