They definitely do. But never underestimate pre-scenting. You get them into feed mode and you have a lot of years of evolution acting behind that very small reptilian brain (which is very primal to begin with).
I have some snakes I know I can reach in when they are in feed mode and others I would not even consider it.
But those 3 points are why when people think that everytime a hand goes into an enclosure a snake will mistake them for food if they feed in the enclosure, that is why it is a myth.