Uh-oh. Here comes temptation -- for a dieter, it's a sweet treat; an alcoholic, a beer; a married man, an attractive, available woman. How to defeat the impulse to gratify desire and stick to your long-term goals of slimness, sobriety, or fidelity?

Here's some advice: Don't stop and think. Thinking may not help.

That is one surprising conclusion of a new study by Loran Nordgren and Eileen Chou at Northwestern University's Kellogg School of Management, published in Psychological Science, a journal of the Association for Psychological Science.

Nordgren and Chou wanted to make sense of two contradictory bodies of literature. "One shows that the presence of temptation contorts cognition in ways that promotes impulsive behavior," says Nordgren. Another shows that "temptation engages protective [thought] processes that promote self-control. You show a dieter a piece of cake, and an early thought is 'I'm dieting' -- and 'no thanks.'"

Both stories leave out a crucial factor, he says: the interaction between temptation and "visceral state" -- hunger, thirst, sexual desire, satiation or craving -- which "dictates whether the same cognitive processes will be oriented toward impulsive behavior or self-control."

The researchers looked at different cognitive mechanisms, including attention and "motivated valuation" -- how much we care about something depending on other rewards -- to see how temptation affected them. In one experiment, 49 male students in committed relationships watched either an erotic film, putting them in an aroused ("hot" visceral) state; or a filmed fashion show, creating a "cool" state. The experimenters then showed them images of attractive women and observed how long they gazed at them. A week later, the procedure was the same, but the men were told the women were incoming students -- thus, available. This time, the aroused men gazed longer. More temptation promoted less fidelity. The cool-state men did the opposite.

In a second study, some of 53 smokers were instructed to smoke directly before the experiment, while the rest abstained for three hours. Then both the satiated and craving groups rated the pleasure of smoking, showing how much they valued cigarettes. Phase two, same conditions, same question -- and a choice: Delay smoking for 40 minutes and earn 3 Euros or smoke immediately and earn nothing. Predictably, the sated smokers more readily delay gratification. But they also rated the pleasure of smoking lower than the first time, whereas the cravers rated it higher. The "cool" group gave themselves reasons to wait; the "hot," to indulge.

What does all this tell us? "If we think of the reason versus passion struggle, we tend to think that cognition serves long-term interests and passion serves immediate gratification -- the angel on one shoulder and the devil on the other," Nordgren explains. "We also think that if you are horny or hungry, your thoughts -- the angel -- are in the right place, but you give into temptation -- the devil.

"This is not accurate, actually. Yes, need or desire abets impulsivity, but it also corrupts the cognitive processes that would help you interrupt that behavior," Nordgren concludes. "When you're craving and being tempted, your rationalization succumbing and so, in a hot state, you have the devil on both shoulders."