Marketers have refined ways to manipulate consumers into changing their habits. An advertisement hovers above a pedestrian in Berlin.

An advertising campaign in Ghana encouraged washing hands with soap to reduce disease.

By CHARLES DUHIGG

Social scientists have known for years that there is power in tying certain behavior to habitual cues through relentless advertising.
The marketing world has used this knowledge to influence consumers. Now the same principles are being applied to a project with a noble purpose - saving lives in the developing world.
Studies show that as much as 45 percent of what we do every day is habitual - that is, performed almost without thinking in the same location or at the same time each day, usually because of subtle cues.
“Habits are formed when the memory associates specific actions with specific places or moods,” said Wendy Wood, a professor of psychology and neuroscience at Duke University in North Carolina. “If you regularly eat chips while sitting on the couch, after a while, seeing the couch will automatically prompt you to reach for the Doritos.”
The urge to check e-mail or to grab a cookie is usually a habit with a specific trigger. Researchers found that most cues fall into four broad categories: a location or time of day, a series of actions, particular moods, or the company of certain people. The e-mail urge, for instance, probably occurs after you’ve finished reading a document or completed a familiar task. The cookie grab probably occurs when you’re walking out of the cafeteria, or feeling sluggish or unhappy.
Aware of this, a self-described “militant liberal” named Val Curtis decided a few years ago that she could help save millions of children from death and disease if they could be trained to form a new habit: wash their hands with soap.
Diseases and disorders caused by dirty hands - like diarrhea - kill a child somewhere in the world about every 15 seconds, and about half those deaths could be prevented with the regular use of soap, studies indicate.
But getting people into a soap habit, it turns out, is surprisingly hard.
So after years spent trying to persuade people in the developing world to wash their hands habitually with soap, Dr. Curtis, an anthropologist then living in Burkina Faso, contacted some of the largest multinational corporations and asked them to teach her how to manipulate consumer habits.
She knew that over the past decade, many companies had perfected the art of creating automatic behaviors - habits - among consumers. These habits have helped companies earn billions of dollars when customers eat snacks, apply lotions and wipe kitchen counters, almost without thinking, often in response to a carefully designed set of daily cues.
“There are fundamental public health problems, like hand washing with soap, that remain killers only because we can’t figure out how to change people’s habits,” Dr. Curtis said. “We wanted to learn from private industry how to create new behaviors that happen automatically.”
If you look hard enough, you’ll find that many of the products we use every day - chewing gums, skin moisturizers, disinfecting wipes, air fresheners - are results of manufactured habits.
“Our products succeed when they become part of daily or weekly patterns,” said Carol Berning, a consumer psychologist who recently retired from Procter & Gamble, the company that sold $76 billion of Tide, Crest and other products last year. “Creating positive habits is a huge part of improving our consumers’ lives, and it’s essential to making new products commercially viable.”
So to teach hand washing, Dr. Curtis persuaded Procter & Gamble, Colgate- Palmolive and Unilever to join an initiative called the Global Public-Private Partnership for Handwashing With Soap. The group’s goal was to double the hand-washing rate in Ghana, where almost every home contains a soap bar but few adults regularly lather up after using the toilet.
Ghana offered a conundrum: Almost half of its people were accustomed to washing their hands with water after using the toilet or before eating. And local markets were filled with cheap, colorful soap bars. But only about 4 percent of Ghanaians used soap as part of their post-toilet hand-washing regime, studies showed.
“We could talk about germs until we were blue in the face, and it didn’t change behaviors,” Dr. Curtis said. So she and her colleagues asked Unilever for advice in designing surveys that ultimately studied hundreds of mothers and their children.
They discovered that previous health campaigns had failed because mothers often didn’t see symptoms like diarrhea as abnormal, but viewed them as a normal aspect of childhood.
The studies also revealed an interesting paradox: Ghanaians used soap when they felt that their hands were dirty - after cooking with grease, for example. This hand-washing habit, studies showed, was prompted by feelings of disgust. And surveys also showed that parents felt deep concerns about exposing their children to anything disgusting.
So the trick, Dr. Curtis and her colleagues realized, was to create a habit wherein people felt a sense of disgust that was cued by the toilet. That disgust, in turn, could become a cue for soap.
A sense of bathroom disgust may seem natural, but in many places toilets are a symbol of cleanliness because they replaced pit latrines. So Dr. Curtis’s group had to create commercials that taught viewers to feel a habitual sense of uncleanliness surrounding toilet use.
Their solution was ads showing mothers and children walking out of bathrooms with a glowing purple pigment on their hands that contaminated everything they touched.
The commercials, which began running in 2003, didn’t really sell soap use. Rather, they sold disgust. Soap was almost an afterthought, but the message was clear: The toilet cues worries of contamination, and that disgust, in turn, cues soap.
“This was radically different from most public health campaigns,” said Beth Scott, an infectious-disease specialist who worked with Dr. Curtis on the Ghana campaign. “There was no mention of sickness. It just mentions the yuck factor. We learned how to do that from the marketing companies.”
By last year, Ghanaians surveyed by members of Dr. Curtis’s team reported a 13 percent increase in the use of soap after the toilet. Another measure showed even greater impact: reported soap use before eating went up 41 percent.
Public health campaigns elsewhere are being revamped to employ habitformation characteristics . One American antismoking campaign is explicitly focused on habits, with commercials intended to teach smokers how to identify what cues tell them to reach for a cigarette.
“For a long time, the public health community was distrustful of industry, because many felt these companies were trying to sell products that made people’s lives less healthy, by encouraging them to smoke, or to eat unhealthy foods, or by selling expensive products people didn’t really need,” Dr. Curtis said. “But those tactics also allow us to save lives. If we want to really help the world, we need every tool we can get.”