TEN years ago, in settling the largest civil lawsuit in American history, Big Tobacco agreed to pay the 50 states $246 billion, which they've used in part to finance efforts to prevent smoking. The percentage of American adults who smoke has fallen since then to just over 20 percent from nearly 30 percent, but smoking is still the No. 1 preventable cause of death in the United States, and smoking-related health care costs more than $167 billion a year. To reduce this cost, the incoming Obama administration should abandon one antismoking strategy that isn't working. A key component of the Food and Drug Administration's approach to smoking prevention is to warn about health dangers: Smoking causes fatal lung cancer; smoking causes emphysema; smoking while pregnant causes birth defects. Compared with warnings issued by other nations, these statements are low-key. From Canada to Thailand, Australia to Brazil, warnings on cigarette packs include vivid images of lung tumors, limbs turned gangrenous by peripheral vascular disease and open sores and deteriorating teeth caused by mouth and throat cancers. In October, Britain became the first European country to require similar gruesome images on packaging. But such warnings don't work. Worldwide, people continue to inhale 5.7 trillion cigarettes annually — a figure that doesn't even take into account duty-free or black-market cigarettes. According to World Bank projections, the number of smokers is expected to reach 1.6 billion by 2025, from the current 1.3 billion. A brain-imaging experiment I conducted in 2006 explains why antismoking scare tactics have been so futile. I examined people's brain activity as they reacted to cigarette warning labels by using functional magnetic resonance imaging, a scanning technique that can show how much oxygen and glucose a particular area of the brain uses while it works, allowing us to observe which specific regions are active at any given time. We tested 32 people (from Britain, China, Germany, Japan and the United States), some of whom were social smokers and some of whom were two-pack-a-day addicts. Most of these subjects reported that cigarette warning labels reduced their craving for a cigarette, but their brains told us a different story. Each subject lay in the scanner for about an hour while we projected on a small screen a series of cigarette package labels from various countries — including statements like “smoking kills” and “smoking causes fatal lung cancers.” We found that the warnings prompted no blood flow to the amygdala, the part of the brain that registers alarm, or to the part of the cortex that would be involved in any effort to register disapproval. To the contrary, the warning labels backfired: they stimulated the nucleus accumbens, sometimes called the “craving spot,” which lights up on f.M.R.I. whenever a person craves something, whether it's alcohol, drugs, tobacco or gambling. Further investigation is needed, but our study has already revealed an unintended consequence of antismoking health warnings. They appear to work mainly as a marketing tool to keep smokers smoking. Barack Obama has said he's been using nicotine gum to fight his own cigarette habit. His new administration can help other smokers quit, too, by eliminating the government scare tactics that only increase people's craving. – New York Times Martin Lindstrom is the author of “Buyology: Truth and Lies About Why We Buy.” __