Psychologist Paul Bloom has written a wonderfully eclectic article for The Atlantic magazine about the psychology of pleasure and why it suggests that we have multiple situation-specific selves.
The piece is a little disjointed in places but it is packed full of information and if nothing else you get a good sense of the enthusiasm for this developing field.
One area of pleasure research not mentioned in Bloom’s piece is the fascinating work of Michel Cabanac, who has a theory that pleasure is the decision-making currency of the brain.
New Scientist had an excellent article on Cabanac’s work which you can read online, and makes an excellent complement to The Atlantic piece.
However, Bloom is more concerned with how we resist the temptation of pleasure using ‘self-binding’ – in other words, doing things that will reduce the chances of us succumbing to temptation later on. Like getting someone to hide your cigarettes if you’re trying to give up.
For adult humans, though, the problem is that the self you are trying to bind has resources of its own. Fighting your Bad Self is serious business; whole sections of bookstores are devoted to it. We bribe and threaten and cajole, just as if we were dealing with an addicted friend. Vague commitments like “I promise to drink only on special occasions” often fail, because the Bad Self can weasel out of them, rationalizing that it’s always a special occasion. Bright-line rules like “I will never play video games again” are also vulnerable, because the Bad Self can argue that these are unreasonable—and, worse, once you slip, it can argue that the plan is unworkable.
For every argument made by the dieting self—“This diet is really working” or “I really need to lose weight”—the cake eater can respond with another—“This will never work” or “I’m too vain” or “You only live once.” Your long-term self reads voraciously about the benefits of regular exercise and healthy eating; the cake eater prefers articles showing that obesity isn’t really such a problem. It’s not that the flesh is weak; sometimes the flesh is pretty damn smart.
Link to Atlantic article ‘First Person Plural’.
Link to NewSci piece ‘The Pleasure Seekers’.
Mind Hacks 
Bloom’s central point, that we have multiple selves, is something that I find hard to believe. I didn’t feel that the examples he cited helped much in supporting the idea.
Everything he talks about can be easily accounted for by differences in someone’s urge or motivational state. I think The Atlantic needs to lay of “neuroscience” articles for a while, as this and the last one (the fMRI article) both fall short of quality science writing.