Experiments have shown that almost all habitual cues fit into one of five categories:

- Location
- Time
- Emotional state
- Other people
- Immediately preceding action

So if you’re trying to figure out the cue for the “going to the cafeteria and buying a chocolate chip cookie” habit, you write down five things the moment the urge hits (these are my actual notes from when I was trying to diagnose my habit):

Where are you? (sitting at my desk)
What time is it? (3:36 P.M.)
What’s your emotional state? (bored)
Who else is around? (no one)
What action preceded the urge? (answered an email)

The next day:
Where are you? (walking back from the copier)
What time is it? (3:18 P.M.)
What’s your emotional state? (happy)
Who else is around? (Jim from Sports)
What action preceded the urge? (made a photocopy)

The third day:
Where are you? (conference room)
What time is it? (3:41 P.M.)
What’s your emotional state? (tired, excited about the project I’m working on)
Who else is around? (editors who are coming to this meeting)
What action preceded the urge? (I sat down because the meeting is about to start)

Three days in, it was pretty clear which cue was triggering my cookie habit—I felt an urge to get a snack at a certain time of day. I had already figured out, in step two, that it wasn’t hunger driving my behavior. The reward I was seeking was a temporary distraction—the kind that comes from gossiping with a friend. And the habit, I now knew, was triggered between 3:00 and 4:00.

The way we habitually think of our surroundings and ourselves create the worlds that each of us inhabit. “There are these two young fish swimming along and they happen to meet an older fish swimming the other way, who nods at them and says ‘Morning, boys. How’s the water?’ ” the writer David Foster Wallace told a class of graduating college students in 2005. “And the two young fish swim on for a bit, and then eventually one of them looks over at the other and goes ‘What the hell is water?’ ”

The water is habits, the unthinking choices and invisible decisions that surround us every day—and which, just by looking at them, become visible again.

Habits, he noted, are what allow us to “do a thing with difficulty the first time, but soon do it more and more easily, and finally, with sufficient practice, do it semi-mechanically, or with hardly any consciousness at all.” Once we choose who we want to be, people grow “to the way in which they have been exercised, just as a sheet of paper or a coat, once creased or folded, tends to fall forever afterward into the same identical folds.”

If you believe you can change—if you make it a habit—the change becomes real.

[...] to modify a habit, you must decide to change it. You must consciously accept the hard work of identifying the cues and rewards that drive the habits’ routines, and find alternatives. You must know you have control and be self-conscious enough to use it [...]

“But what was really interesting were the near misses. To pathological gamblers, near misses looked like wins. Their brains reacted almost the same way. But to a nonpathological gambler, a near miss was like a loss. People without a gambling problem were better at recognizing that a near miss means you still lose.”

[...] in landing a job, Granovetter discovered, weak-tie acquaintances were often more important than strong-tie friends because weak ties give us access to social networks where we don’t otherwise belong.

The Montgomery bus boycott became a society-wide action because the sense of obligation that held the black community together was activated soon after Parks’s friends started spreading the word. People who hardly knew Rosa Parks decided to participate because of a social peer pressure—an influence known as “the power of weak ties”—that made it difficult to avoid joining in.

When WIOQ first started playing “Hey Ya!” in early September—before the sandwiching started—26.6 percent of listeners changed the station whenever it came on. By October, after playing it alongside sticky hits, that “tune-out factor” dropped to 13.7 percent. By December, it was 5.7 percent. Other major radio stations around the nation used the same sandwiching technique, and the tune-out rate followed the same pattern.

And as listeners heard “Hey Ya!” again and again, it became familiar. Once the song had become popular, WIOQ was playing “Hey Ya!” as many as fifteen times a day. People’s listening habits had shifted to expect—crave, even—“Hey Ya!” A “Hey Ya!” habit emerged. The song went on to win a Grammy, sell more than 5.5 million albums, and earn radio stations millions of dollars.

“Sometimes stations will do research by calling listeners on the phone, and play a snippet of a song, and listeners will say, ‘I’ve heard that a million times. I’m totally tired of it,’ ” Meyer told me. “But when it comes on the radio, your subconscious says, ‘I know this song! I’ve heard it a million times! I can sing along!’ Sticky songs are what you expect to hear on the radio. Your brain secretly wants that song, because it’s so familiar to everything else you’ve already heard and liked. It just sounds right.”

[...] despite those lists, more than 50 percent of purchasing decisions occurred at the moment a customer saw a product on the shelf, because, despite shoppers’ best intentions, their habits were stronger than their written intentions. “Let’s see,” one shopper muttered to himself as he walked through a store. “Here are the chips. I will skip them. Wait a minute. Oh! The Lay’s potato chips are on sale!” He put a bag in his cart. Some shoppers bought the same brands, month after month, even if they admitted they didn’t like the product very much (“I’m not crazy about Folgers, but it’s what I buy, you know? What else is there?” one woman said as she stood in front of a shelf containing dozens of other coffee brands). Shoppers bought roughly the same amount of food each time they went shopping, even if they had pledged to cut back.

“Consumers sometimes act like creatures of habit, automatically repeating past behavior with little regard to current goals,” two psychologists at the University of Southern California wrote in 2009.

“You never want a serious crisis to go to waste,” Rahm Emanuel told a conference of chief executives in the wake of the 2008 global financial meltdown, soon after he was appointed as President Obama’s chief of staff. “This crisis provides the opportunity for us to do things that you could not do before.” Soon afterward, the Obama administration convinced a once-reluctant Congress to pass the president’s $787 billion stimulus plan. Congress also passed Obama’s health care reform law, reworked consumer protection laws, and approved dozens of other statutes, from expanding children’s health insurance to giving women new opportunities to sue over wage discrimination. It was one of the biggest policy overhauls since the Great Society and the New Deal, and it happened because, in the aftermath of a financial catastrophe, lawmakers saw opportunity.

“It might have been hard at another company to fire someone who had been there so long,” O’Neill told me. “It wasn’t hard for me. It was clear what our values dictated. He got fired because he didn’t report the incident, and so no one else had the opportunity to learn from it. Not sharing an opportunity to learn is a cardinal sin.”

Small wins are exactly what they sound like, and are part of how keystone habits create widespread changes. A huge body of research has shown that small wins have enormous power, an influence disproportionate to the accomplishments of the victories themselves. “Small wins are a steady application of a small advantage,” one Cornell professor wrote in 1984. “Once a small win has been accomplished, forces are set in motion that favor another small win.” Small wins fuel transformative changes by leveraging tiny advantages into patterns that convince people that bigger achievements are within reach.

When people start habitually exercising, even as infrequently as once a week, they start changing other, unrelated patterns in their lives, often unknowingly. Typically, people who exercise start eating better and becoming more productive at work. They smoke less and show more patience with colleagues and family. They use their credit cards less frequently and say they feel less stressed. It’s not completely clear why. But for many people, exercise is a keystone habit that triggers widespread change. “Exercise spills over,” said James Prochaska, a University of Rhode Island researcher. “There’s something about it that makes other good habits easier.”

After the death of Dungy’s son, the team started playing differently. A conviction emerged among players about the strength of Dungy’s strategy. In practices and scrimmages leading up to the start of the 2006 season, the Colts played tight, precise football.

“Most football teams aren’t really teams. They’re just guys who work together,” a third player from that period told me. “But we became a team. It felt amazing. Coach was the spark, but it was about more than him. After he came back, it felt like we really believed in each other, like we knew how to play together in a way we didn’t before.”

For the Colts, a belief in their team—in Dungy’s tactics and their ability to win—began to emerge out of tragedy. But just as often, a similar belief can emerge without any kind of adversity.

Belief was the ingredient that made a reworked habit loop into a permanent behavior.

“I wouldn’t have said this a year ago—that’s how fast our understanding is changing,” said Tonigan, the University of New Mexico researcher, “but belief seems critical. You don’t have to believe in God, but you do need the capacity to believe that things will get better.

“Even if you give people better habits, it doesn’t repair why they started drinking in the first place. Eventually they’ll have a bad day, and no new routine is going to make everything seem okay. What can make a difference is believing that they can cope with that stress without alcohol.”