Faced with a risk of communicable diseases, humans tend to be very responsive, altering their behavior and taking preventative measures. There are well understood risk factors for things like Lyme disease and hantavirus, and many people have managed to change their habits to minimize risk. Faced with the risk of a noncommunicable disease, like cancer or heart disease, we don't tend to do nearly as well, even when the risks are equally well understood.

Why are we so lousy at simple things like eating well and avoiding cigarettes? A perspective in this week's Science (part of a series on noncommunicable diseases) suggests we've been going at the problem all wrong. In general, we've been asking people to step back and think about things like eating well. But the authors of this piece point out that a lot of our problems take place precisely when we're not bothering to think. And the only way around that issue may be a bit of social engineering.

Many approaches to public health are based on what has been called the deficit model, which assumes that people just don't know enough about the risks associated with problematic behavior. If we just get them enough information, and maybe provide a bit of encouragement, then they'll stop smoking. Or hit the salad bar. Or do whatever is necessary to reduce their health risks.

It doesn't work that way. "To date, interventions aimed at changing such behaviors have largely encouraged people to reflect on their behaviors," the authors write. "These approaches are often ineffectual, which is in keeping with the observation that much human behavior is automatic, cued by environmental stimuli, resulting in actions that are largely unaccompanied by conscious reflection."

The problem, as the authors outline it, is that careful consideration takes time and energy, and most people don't have a lot of either to spare. And when we're not consciously thinking about our actions, we tend to give in to bad habits or various forms of self-gratification.

But it's precisely because we're not bothering to think about things that we are left wide open to subtle manipulation. The authors cite a variety of studies that have shown very subtle changes can get people to make healthier choices. Having more stairs and making them more obvious will mean more people take them. Placing the healthier choices at salad bars closer to the edges gets more people to select them. And so on.

New York City has actually provided a prime example of how this can play out in the real world. Education programs about the health risks of smoking have existed for decades. But, over the span of a few years, the city banned smoking in public places and raised the tax on cigarettes dramatically (it also made it much easier to enroll in cessation programs). By raising the barrier to bad habits and turning the choice of buying a pack of cigarettes into something that people were consciously aware of, the city managed to dramatically reduce smoking rates.

Now, it's attempting to do the same with sugared drinks by putting a limit on the size of sweetened beverage servings. Since people will tend to buy one of whatever's available, the policy will almost certainly cut down on the amount of sugar consumed in the city, which is likely to have an effect on obesity and all the health problems associated with it.

Compared to some methods advocated in this perspective, modifying soda sizes is a relatively hands-off approach. For example, to get people more exercise, the authors suggest we might "consider making the elevator a less appealing option by increasing the effort required to use it. For example, slowing down the speed at which elevator doors close, thus increasing the journey time, increases stair use." In other words, making the experience annoying may be the best way to get people to change their habits.

But there's already a backlash against the (relatively minor) social engineering involved in the soda policy. Some of this is push-back from commercial interests like soda distributors; the authors recognize that these sorts of behavioral efforts pose a threat to "economies that are built on excessive consumption."

Not all of this is economic self-interest, however. These rules can obviously be viewed as providing a benefit to the city's residents, both in terms of health and in terms of reducing the social burden of medical costs. But people can reasonably disagree over how aggressively the government should pursue those benefits at the expense of making everyday life a bit more annoying for some of its residents.

Science, 2012. DOI: 10.1126/science.1226918 (About DOIs).