I believe, the severity of stuttering I would say, is mainly contributed to: (1) stuttering **anticipation**, reliance on secondaries / avoidance behaviors, and understandings / beliefs that trigger blocks (which result from past experiences of one’s speaking leading to negative consequences, including punishment, rejection, misunderstandings and other negative listener responses). Research shows that close to the stuttering onset, children who stutter (CWS) do not **anticipate** their moments of stuttering. (probably because they have not yet had enough experience of when it occurs). Then their **anticipation** increases until it finally reaches the point where, as adults, they accurately **anticipate 90%** of upcoming stuttering. The trouble is that this sort of anticipation is probably a sort of self-fulfilling prophesy). Correct me if I'm wrong. In my understanding, babies with neurogenic stuttering (whose cause is stroke or brain damage) - they start stuttering on their first words. In contrast, this is not the case in babies with developmental stuttering, where stuttering emerges after a period of extensive learning. Children don’t stutter on their first words because they haven’t yet developed the language to make speech complex. Typically, stuttering begins around the time that children are putting a few words together in the phase of error-repairs (which is the word-combination phase in which they assign importance to certain words). Regarding developmental stuttering: A subset of stutterers with genetic or neurological underpinnings (e.g., hypersensitivity to sensory feedback, abnormally slow or impaired speech planning or speech motor control abilities, or abnormalities in dopamine metabolism) - are relatively slow at speech planning in general and make somewhat more speech planning errors than non-stutterers. Their speech motor control abilities are somewhat below average, but not sufficiently so for them (or their listener) to be consciously aware that they are impaired. Conclusion: So, I hypothesize that genetics and neurology may predispose to stuttering but their contribution is much less important than that of our understandings and beliefs: stuttering is primarily a cognitive disorder. Risk factors that are associated with recovered and persistent stuttering, are not necessarily causally related to recovery and persistence. Additionally, functional neurological differences are likely significantly influenced by moments of stuttering at the state level, in contrast to the general traits of developmental stuttering. In other words, I think that the primary blocks are mainly contributed to operant conditioning, which is the poor fine-tuning of the (inhibitory) protection mechanism responsible for the ordinary moment to moment regulation of whether or not we speak our thoughts out loud. So, even though our conscious intellect may tell us that it would be good to say that word or phrase out loud, if we raise this protection mechanism too high (e.g., due to perceived errors in the upcoming speech plan - like anxiety, stress or anticipation, or identity-conflict), then this mechanism decreases post-synaptic dopamine resulting in the speech plan getting cancelled, and then the nerve impulses that are required to execute the speech plan is not generated - resulting in primary blocks. If young children further poorly fine-tune this protection mechanism, this could then turn into a self-sustaining vicious circle: People who stutter tend to evaluate blocks negatively, our negative evaluations of our blocks then lead to further inhibition of speech motor execution (i.e., further blocks) in the future, even when the underlying predisposing factors are no longer present. Therefore, I think we should understand that (1) being unaware of an underlying mild speech-production impairment, or (2) distorted perceptions of how perfect speech needs to be, or (3) perceiving it as a problem that listeners (like parents) are incapable of understanding us or unwilling to try, no matter how perfectly we speak - that this can result in this protection mechanism to rise too high and prevent the stutterer getting the words out. So, if we continue perceiving listener's reactions as a problem, the stutter disorder increases because the excessive rise may happen again because previous rises in the protection mechanism have not resulted in an adequate increase in the quality of our speech.