Courtesy of Da Capo Lifelong Books
How long does it take to form a new habit? Say you want to go to the gym regularly, eat more fruit, learn a new language, make new friends, practice a musical instrument, or achieve anything that requires regular application of effort over time. How long should it take before it becomes a part of your routine rather than something you have to force yourself to do?
I looked for an answer the same way most people do nowadays: I asked Google. This search suggested the answer was clear-cut. Most top results made reference to a magic figure of 21 days. These websites maintained that “research” (and the scare-quotes are fully justified) had found that if you repeated a behavior every day for 21 days, then you would have established a brand-new habit. There wasn’t much discussion of what type of behavior it was or the circumstances you had to repeat it in, just this figure of 21 days. Exercise, smoking, writing a diary, or turning cartwheels; you name it, 21 days is the answer. In addition, many authors recommend that it’s crucial to maintain a chain of 21 days without breaking it. But where does this number come from? Since I’m a psychologist with research training, I’m used to seeing references that would support a bold statement like this. There were none.
My search turned to the library. There, I discovered a variety of stories going around about the source of the number. Easily, my favorite concerns a plastic surgeon, Maxwell Maltz, M.D. Dr Maltz published a book in 1960 called Psycho-Cybernetics in which he noted that amputees took, on average, 21 days to adjust to the loss of a limb and he argued that people take 21 days to adjust to any major life changes.1 He also wrote that he saw the same pattern in those whose faces he had operated on. He found that it took about 21 days for their self-esteem either to rise to meet their newly created beauty or stay at its old level.
The figure of 21 days has exercised an enormous power over self-help authors ever since. Bookshops are filled with titles like Millionaire Habits in 21 Days, 21 Days to a Thrifty Lifestyle, 21 Days to Eating Better, and finally, the most optimistic of all: 21-Day Challenge: Change Almost Anything in 21 Days (at least it acknowledges that it might be a challenge!). Occasionally, the 21- day period is deemed a little too optimistic and we are given an extra week to transform ourselves. These more generous titles include The 28-Day Vitality Plan and Diet Rehab: 28 Days to Finally Stop Craving the Foods that Make You Fat.
Whether 21 or 28 days, it’s clear that what we eat, how we spend money, or indeed, anything else we do, has little in common with losing a leg or having plastic surgery. To take Dr Maltz’s observations of his patients and generalize them to almost all human behavior is optimistic at best. It’s even more optimistic when you consider the variety amongst habits. Driving to work, avoiding the cracks in the pavement, thinking about sports, walking the dog, eating a salad, booking a flight to China; they could all be habits and yet they involve such different areas of our lives. But, to be fair, Maltz didn’t invent the 21-day time frame; there are all sorts of origin stories explaining its whereabouts, most of them standing on science-free ground.
Thanks to recent research, though, we now have some idea of how long common habits really take to form. In a study carried out at University College London, 96 participants were asked to choose an everyday behavior that they wanted to turn into a habit.2 They all chose something they didn’t already do that could be repeated every day; many were health-related: people chose things like “eating a piece of fruit with lunch” and “running for 15 minutes after dinner.” Each of the 84 days of the study, they logged into a website and reported whether or not they’d carried out the behavior, as well as how automatic the behavior had felt. As we’ll soon see, acting without thinking, or “automaticity,” is a central component of a habit.
So, here’s the big question: How long did it take to form a habit? The simple answer is that, on average, across the participants who provided enough data, it took 66 days until a habit was formed. And, contrary to what’s commonly believed, missing a day or two didn’t much affect habit formation. The complicated answer is more interesting, though (otherwise, this would be a short book). As you might imagine, there was considerable variation in how long habits took to form depending on what people tried to do. People who resolved to drink a glass of water after breakfast were up to maximum automaticity after about 20 days, while those trying to eat a piece of fruit with lunch took at least twice as long to turn it into a habit. The exercise habit proved most tricky with “50 sit-ups after morning coffee,” still not a habit after 84 days for one participant. “Walking for 10 minutes after breakfast,” though, was turned into a habit after 50 days for another participant.
The graph shows that this study found a curved relationship between repeating a habit and automaticity. This means that the earlier repetitions produced the greatest gains towards establishing a habit. As time went on these gains were smaller. It’s like trying to run up a hill that starts out steep and gradually levels off. At the start you’re making great progress upwards, but the closer you get to the peak, the smaller the gains in altitude with each step. For a minority of participants, though, the new habits did not come naturally. Indeed, overall, the researchers were surprised by how slowly habits seemed to form. Although the study only covered 84 days, by extrapolating the curves, it turned out that some of the habits could have taken around 254 days to form—the better part of a year!
What this research suggests is that 21 days to form a habit is probably right, as long as all you want to do is drink a glass of water after breakfast. Anything harder is likely to take longer to become a really strong habit, and, in the case of some activities, much longer. Dr Maltz and his cheerleaders weren’t even close, and all those books promising habit change in only a few weeks are grossly optimistic. Of course, this study opens up a whole new set of questions. The participants were only trying to adopt new habits; what about our existing habits? How much better might they have done using tried and tested psychological techniques? And this study doesn’t really tell us what a habit feels like, how we experience it, or where it tends to happen.