Based on bromden's flashbacks, what elements from his history do we know?

Bromden remembers something about his childhood from his flashback that he had the element of faking as deaf because he doesn't feel he will be heard if he speaks, and he hears more when he is deaf because people think he can't hear anyways. Due to this, we know from his history that this flashback was an important and meaningful moment for Bromden because it triggered changes and realization to himself why he chose to start acting deaf.