If you ask people how much they plan to exercise, they'll exercise more—but only if that's a personal goal, according to a new study in the Journal of Consumer Research.

"When people have set for themselves targets about how much they should engage in a behavior (say, if the behavior is how much to exercise per week), asking them to predict whether they will exercise in the next week makes them think about what they think they should do," write authors Pierre Chandon (INSEAD), Ronn J. Smith (University of Arkansas), Vicki G. Morwitz (New York University), Eric R. Spangenberg, and David E. Sprott (both Washington State University). "This reduces the chances that they will simply repeat their past behavior and hence breaks their habits."

The researchers also confirmed that we are creatures of habit: When people did not have strong personal goals for how much they should engage in a particular behavior (like watching the news), asking them to predict how much they would watch the news resulted in strengthening their existing habits.

The researchers discovered the pattern across a number of different behaviors among participants in the United States and France. "We asked a group of people to predict whether or not they would engage in a particular behavior in the next week or month and did not ask the same question to a control group," the authors explain. "To measure habits, we collected data about behavior frequency and duration both before and after the time of the behavior prediction question."

In one experiment, the authors asked college students to predict whether they would read books or watch the news in the next week. "Compared to a control group, students asked to predict their behavior were more likely to repeat what they had done in the week before," the authors explain. "However, the same question disrupted habits for exercising, a behavior for which our participants held strong personal norms." Asking about future exercising led to an estimated 94 additional minutes of exercising (+ 138 percent) for students who had only exercised for 10 minutes in the week before.

"These findings have important implications, not only for those of us who are attempting to keep our New Year's resolutions, but also for managers or policy makers attempting to reinforce valuable habits and to disrupt harmful ones," the authors conclude.