A recent review article by T. F. Heatherton and D. D. Wagner draws many studies together in support of a simple view of temptation and resisting temptation. The latter is also known as self-regulation. That’s what you exhibit when you do not do something that conflicts with your long term goals, even though it is something you would quite enjoy doing.
The view, referred to as a “balance model”, comes complete with an illustration of a beam balanced on a fulcrum. The beam may tip in the direction of giving into temptation for two kinds of reasons. One is that the temptation, or the pleasure anticipated from it, becomes more forcefully represented. That might happen because of signs of the temptation’s presence or easy availability, like the smell of tobacco smoke, or the sight of a high calorie food.
The other route to tipping the balance toward temptation is weakening of the opposition to giving in to temptation. That might happen because of fatigue, drug indulgence (most familiarly, alcohol), disease, or interference from passing a strong electromagnet near the head (TMS: transcranial magnetic stimulation).
The article cites evidence that opposition to giving into temptation importantly involves the prefrontal cortex (PFC). In contrast, different temptations are reflected in increased activation of neurons in different brain regions. Fortunately, the PFC has connections to these different regions, and rise in activity in PFC neurons tends to lower activity in neurons in these other regions.
The struggle to resist temptation, then, is reflected in the competition between activity in the PFC and activity in regions it’s connected to that are turned on by reminders of rewards that you would enjoy, but that would conflict with your longer term goals.
As noted, this balance model rests on many studies, so it has a lot going for it. There is, however, a minor oddity in the description that goes with this model. The article’s authors contrast brain regions representing the value of a tempting stimulus with “prefrontal regions associated with self-control” (pp. 134-135). They refer to the idea that “resisting temptations reflects competition between impulses and self-control” (p. 136).
It would be more natural to think of the opposition as a tension between regions that represent the attractions of immediately available temptations, and a region that represents long term goals. It is, after all, the achievement of long term goals that is the reason for resisting temptations, and it should be increased activation of representation of long term goals that competes with representation of immediate pleasures.
If we think of the PFC as representing long term goals, we can properly locate “self control” as a feature of the person whose brain houses both the PFC and the other regions that represent temptations. Self control is what you (the whole of you) exhibit when you avoid treating yourself to an immediately available pleasure, where indulging in it would conflict with a long term goal (sobriety; weight loss; avoidance of STDs, saving money for the future, and so on). The PFC is only a part of you. Activation of its neurons can certainly inhibit activation of neurons in other regions, but it is not a self, and it’s not the right kind of thing to exert “self control”.
If we think of the PFC as representing long term goals, its ability to inhibit activity in a variety of other regions also seems quite natural. After all, to hold a long term goal is to be directed on a result in the face of whatever obstacles may present themselves. We are not omniscient. We do not know in advance what the obstacles to a long term goal will be. So, the more temptation-promoting brain regions our representations of long term goals are able to inhibit, the more useful they will be to us.
[The model discussed here is found in Heatherton, T. F and Wagner, D. D. (2011) “Cognitive neuroscience of self-regulation failure”, Trends in Cognitive Science 15(3):132-139.]