When the go brain gets the advantage, as through a surge in dopamine, it can have us acting on an impulse before the stop brain even wakes up to the situation. At the same time, the stop brain is vulnerable to innumerable influences that can keep it from stirring, irrespective of how powerful the go brain is. The stop brain needs information, for instance, in order to sense that there might be trouble, and so anything that keeps us from collecting that information will put the stop brain to sleep.
