The word “choosing” is not the most accurate. We have chosen to block in the same way someone “chooses” a harmful romantic partner to cope with something else unbearable. The academic research is pretty clear on this pattern : after enough episodes of perceiving that your repetitions are too bizarre to let others hear, your brain subconsciously searches for a solution. For many of us, that’s “just try harder to force the word out, avoid looking at your listener., and avoid the word/situation all together” This results in an involuntary valsalva maneuver, restricting flow of breath.