In Cialdini's amazing book "Influence: The Psychology of Persuasion" the author notes how framing the way an individual sees themselves can change their actions. For example, ask someone if they're a "good person." They'll say yes. Then you say, "well, good people give to charity. Would you like to support
So in this case do you think the Nobel Peace Prize is the equivalent of asking Obama "are you a peaceful person?" and it will influence his future policy decisions? I mean, the Nobel Peace Prize winner shouldn't be belligerent and aggressive, right?
Obviously Obama is a bright and self-aware President, and US policy is often the product of politics, not any one individual, but at the margins maybe this impacts the expectations Obama sets for himself during the course of his Presidency.
[personally i'm an Obama fan so this post has less to do w/ a commentary on his politics and more to do with behavioral science]