I assume it gets reward for getting points in the pacman game (eating dots and ghosts) and presumably loses them if it dies or loses the game. There might also be a time factor involved so it doesn't waste time.

I'm really not entirely sure how it's decision making process works and I'm really curious to know. Because simulating every possibility would be ridiculous, but trying to predict the distant future based on some small action that happens in the present is also really difficult.

>So while this is intelligence, this is not sentience.

No one is claiming it is, and "sentience" is a really dubious concept itself.