In “The Picture of Dorian Gray,” Dorian learns that after he spurned the girl who loved him, she died—presumably by her own hand. He insists that he had resolved to marry her after all, but his resolution came too late. Resolutions, as Oscar Wilde knew, are problematic. Dorian’s patron, Lord Henry, when he hears Dorian’s excuses, declares, “Good resolutions are useless attempts to interfere with scientific laws. Their origin is pure vanity. Their result is absolutely nil.”
Photograph by Harold M. Lambert / Lambert / Getty

Not quite, but close. When the psychologist John Norcross researched New Year’s resolutions, in the nineteen-eighties, he found that more than fifty per cent of Americans made some sort of resolution. After six months, only forty per cent had stuck with it. When Norcross followed up two years later, the number had dropped to nineteen per cent. Even among the successes, more than half had experienced lapses—fourteen, on average. Still, we keep telling ourselves that we can lose weight, save money, and go to the gym.

It turns out that timing is important in determining whether or not we succeed. In May, 2012, Katherine Milkman, a behavioral economist at the University of Pennsylvania, was invited to the PiLab Summit, an annual gathering of social-science researchers convened by Google to discuss ways of making the company more productive. Milkman found herself in a discussion about “nudges”—small environmental interventions that could shift people’s behavior. “In the course of the conversation, someone posed a question, ” Milkman recalled. “When would nudges be the most effective?” Milkman’s research hadn’t focussed on that particular aspect of nudges, but, she said, “I had a strong instinct that they’d be more effective at turning points—moments that feel like a new beginning.”

When Milkman returned to Philadelphia, she teamed up with two colleagues, Jason Riis and Hengchen Dai, to see if the idea of temporal turning points held any merit. In a series of studies, forthcoming from the journal Management Science, Milkman, Riis, and Dai found that fresh starts do push us to change our behavior. The beginning of a week, a month, or a year forms what the psychologist Richard Thaler calls a “notational boundary.” With that, researchers suspect, comes a sense of optimism, the promise of “a new me,” as Milkman put it. To test that theory, her team looked at daily Google searches for the term “diet” over a period of nine years. They found that searches followed a predictable cycle: they peaked at the start of any given week, month, or year, then gradually tapered off. The largest increase—eighty-two per cent above the baseline—occurred immediately after New Year’s.

Milkman and her colleagues then looked at behavior by tracking the gym attendance of nearly twelve thousand undergraduates over a year and a half by measuring the participants’ average number of visits. Gym attendance peaked in January, they found, and decreased in the following months. Smaller spikes occurred at the beginning of each week, each month, and each term.

Finally, the researchers looked at commitments on a Web site called stickK, which allows you to set a goal and contractually determine the consequences for failing to attain it, ranging from community sanctions to monetary payments. (If you don’t lose those ten pounds, you’ve agreed to donate fifty dollars to a political party that you loathe.) After tracking forty-three thousand people over two and a half years, the team found that the greatest number of contracts—a hundred and forty-five per cent above the average rate—were signed at the start of the new year. Throughout the year, each week and each month had a mini-cycle of its own, with the beginning of the week corresponding to a sixty-three-per-cent increase. “Every week brings a new opportunity,” Riis says. “And people take advantage of that, whether or not they know it.”

This sensibility even influences the stock market. In a phenomenon known as the January Effect, the market always performs better than average at this time of year. Recent evidence suggests part of the explanation lies in simple optimism: in January, we take a rosier view of the future, and tend to bid up uncertain stocks. (They subsequently fall back to their real value.)

Optimism, then, isn’t always constructive. If we’re too positive, we condemn ourselves to fail. Many backsliders relapse because they have overestimated their own abilities, underestimated the time and effort involved in staying the course, or have an exaggerated view of the effect that the change would have on their lives. “We underestimate these fluctuations in self-control and motivation,” Riis said. “In the moment of exuberance, it’s easy to forget how much we won’t feel like exercising.” The psychologists Janet Polivy and Peter Herman call this the false-hope syndrome: unrealistic expectations about our ability to change, followed closely by the dashing of our initially high aspirations.

Naturally, if you set more realistic goals, you are more likely to succeed. In a study that looked at the role of expectations in exercise, the psychologist Fiona Jones and her colleagues found that people with more modest expectations were far likelier to complete a twelve-week-long exercise course. And once we’ve set goals, we’re most likely to reach them by creating a firm plan. The theory of implementation intentions, a term coined by the psychologist Peter Gollwitzer, maintains that we have a better chance of sticking to a goal if we think about contingencies in advance and devise a direct, automatic response to each of them. (If feel too tired to go to the gym, I’ll have some coffee or eat an apple before heading out.) “It’s harder to break a specific commitment then a nonspecific one,” Milkman said.

Anecdotal evidence suggests that one’s commitment to a determined spouse can also be helpful. “I haven’t had a cigarette in probably six years,” President Obama said in September. “That’s because I’m scared of my wife.”

But it’s never easy. Milkman’s colleague Hengchen Dai tried to apply her team’s insights to help her quit biting her nails: “Once it worked for three months, which is a long time for me,” she said. Her cuticles were in good shape. “But then I bit them once, and I couldn’t stop.” In those moments of relapse, Dai said, she reflects on the premise of fresh starts. “If we help people realize how many opportunities there are, they can put their imperfections behind them.” As for her nails? “Maybe I’ll try again on New Year’s.”

Maria Konnikova is the author of “Mastermind: How to Think Like Sherlock Holmes.”