What is the scientific goal of Artificial Intelligence?

1) To have a better understanding of the human brain, and prove this by immitating it in robots.
2) To create machines that will seem like humans, but will have a better and more predictable behaviour.
3) To create machines that are capable of doing work that no human can.
4) To understand intelligence by building computer programs that exhibit intelligent behaviour.

What do you think? For me 2nd option sound best.