For years (and years and years), physicians treated stomach ulcers by telling their patients to avoid spicy foods and stressful situations. The result? People with ulcers were transformed into people with bland diets, boring lives, and ulcers.

It was later discovered that the conventional wisdom about the cause of ulcers was simply hogwash. Australian researchers Barry Marshall and Robin Warren turned the gastrointestinal world upside down when they proved that most ulcers were caused by a bacterial infection. Once the scientists got to the real source of the problem, a far more effective intervention was obvious: the use of antibiotics to eradicate the Heliobacter pylori bug.

We assume that the cause of poor behavior is a lack of information, inadequate incentives, or sloppy decision-making.

In the case of ulcers, a treatment revolution occurred after someone corrected a false assumption about the cause of the problem. We’re undergoing a similar revolution when it comes to behavioral change, and here’s why.

When we see other people acting in ways that don’t make a lot of sense, our knee-jerk reaction is to try to change their minds–to convince them to do something differently. Implicitly or explicitly, we assume that the cause of poor behavior is a lack of information, inadequate incentives, or sloppy decision-making. Understandably, we work on persuading them to do the right thing.

It rarely works. We argue until we’re blue in the face, but our colleagues or loved ones stick to their bad habits. They interrupt people in meetings or don’t finish their work on time. Or they eat and drink too much, avoid exercise and save too little money, and sleep and rest far too inconsistently. (And so do we.)

Take the case of saving for retirement: It’s obviously good for us, but without some help few of us save as much as we need. In 2001, the researcher David Laibson and his colleagues reported on a company that was offering educational seminars on its 401(k) program and found that some of the employees attending weren’t participating in the savings program at all; others were enrolled but weren’t saving as much as they could.

On the face of it, these educational sessions were highly persuasive. After attending the meetings, 100% of the employees who weren’t participating in the program said they planned to join–but fewer than one in seven of them actually followed through. (Laibson found a similar pattern of good intentions staying dormant among the 401(k) participants who, after attending the seminar, planned to adjust their contributions–very few of whom actually did so.)