He's not able to because he wants you to think he knows a lot so that you look into his work and buy his books. There is a reason he only promotes one persons "research". I've debunked him before, yet here he is doubling down. He's using one area of neuroscience related to dopamine and thinking there is an association to stuttering. It's a different mechanism entirely, associated with different brain regions than what stuttering is associated with. This is the dunning-kruger effect at play.