Whether stuttering began at age 4 or 7 or 9 or 13. I think a genetic predisposition may already have been present at a neurological level Then. If certain cues or stimuli then lead the subconscious mind to develop learned helplessness around speech-plan execution, the process could become self-reinforcing and gradually disrupt how the nervous system responds to the inner judge’s evaluative process at the moment of speech production/execution. This is simply my own interpretation of the stutter cycle or loop. Your thoughts?