The 2011 book by David DiSalvo, WHAT MAKES YOUR BRAIN HAPPY AND WHY YOU SHOULD DO THE OPPOSITE, was recommended to me by a friend. I read it, and am glad I did. For me, this book explained a lot.
DiSalvo's basic premise is this: The human brain evolved to conserve its resources in everyday life, so as to save them for the life-threatening situations where they are really needed. Thus, your brain will usually take the "easy way out" because any other way creates mental discomfort. This discomfort can be detected with functional MRI, where during some kinds of decision-making, the parts of the brain light up that cause anxiety (such as the amygdalae), and the parts that produce reward-feeling rev down (ventral striatum).
What kind of decisions? Those that go against the norms of one's peer group, or seem likely to cause friction with people one cares about, or will entail risk to something you value: security, belonging, comfort, reputation. The result is that we try to minimize this discomfort by looking only at evidence that confirms what we already believe and discounting evidence that doesn't. Your brain wants consistency and certainty. It even wants to "coast" if it can: Some studies show that for between 30 to 50 percent of our waking time, most of us are mentally "elsewhere," operating on automatic pilot. This is why, for instance, you find yourself driving to your job when it's Saturday and you meant to go to the dry cleaner's.
Alas, in order to be just, or creative, or even fully aware of the world, consistency and certainty often must be sacrificed. This may be why artists are so often prone to depression. The world looks more chaotic to their driven, not-at-ease brains.
There is a lot more about neural activity in this fascinating book. Highly recommended.