Science Says It Takes This Long to Form a Habit

Here's what goes on in your brain when you make a resolution, and how long it might take for it to stick. (Hint: It's not 21 days.)

Sabrina Stierwalt, PhD
4-minute read
Episode #358
The Quick And Dirty
  • Despite popular lore, it takes an average of 66 days for a new behavior to become a habit.
  • For some it takes less far less time (as little as 18 days) and for others it takes far more time (over 250 days).
  • There are tricks to help improve your chances of success in forming a new habit, like beginning the new behavior while on vacation.

Flossing every day, running more, eating more vegetables—whatever our goals, around four in ten of us will make resolutions to improve ourselves in the new year. But how many actually keep them? 

One relatively optimistic study that followed a group making new year’s resolutions for six months found that 46 percent were still on track by the end of June. However, a quick google search turns up numerous references to the fact that 80 percent of new year’s resolutions fail by the second week of February. As far as I can tell, these mentions all trace back to a single place: a US News article that does not cite the statistic or link it to any study. But the article is written by a clinical psychologist. Let’s at least assume that, for those of us looking to make a change, the statistics aren’t in our favor.

So, how can we get our new habits to stick? What happens in our brain when we create a habit and how long does it take before a behavior becomes second nature?

Brain Anatomy of Habit Formation

A group of nuclei embedded in the midbrain, called the basal ganglia, deals with adopting new, goal-driven actions and integrating them into our consistent behaviors. The basal ganglia also deal with memory, pattern recognition, and motor control, and these nuclei are deeply connected to other parts of the brain.

Studies of brain activity suggest that a key point in habit formation occurs when the basal ganglia take over for the prefrontal cortex.

The prefrontal cortex, the frontmost part of the frontal lobe, deals with decision-making. Studies of brain activity suggest that a key point in habit formation occurs when the basal ganglia take over for the prefrontal cortex. 

How long does it take to form a habit?

Again turning to popular internet lore, the most commonly quoted number is that it takes 21 days to form a habit. This belief apparently originates from Psycho-Cybernetics, a book published in the1960s by plastic surgeon Maxwell Maltz.

Maltz noticed that his plastic surgery patients took 21 days, on average, to get used to seeing their new faces in the mirror. His amputee patients still felt their phantom limbs for roughly the same amount of time. He extrapolated that it takes at least 21 days for something to become second nature to us humans. Although Maltz was careful not to claim his observations as facts, society quickly adopted the 21-days myth.

On average, it took participants in a 2009 study 66 days to solidify their new habit.

Dr Phillippa Lally and her collaborators conducted a more rigorous study in 2009. Researchers recruited 96 people who were interested in forming a new, daily habit like, say, drinking a glass of water before bed, and monitored them over 12 weeks. Each day participants were asked to self-report on how “automatic” their new, self-chosen habit felt, including whether it felt “hard not to do” or if they could do it “without thinking.” 

The results were … let’s say highly varied. For some participants, they only needed 18 days for a behavior to become a habit. For others, their adopted behaviors still didn’t feel like second nature after 254 days, although the researchers predicted the hold-outs would get there eventually. So, on average, it took participants 66 days to solidify their new habit. 

How can you make a new habit stick?

There is no definitive study on what makes a habit stick. But we do have plenty of advice from neuroscientists and psychologists based on their experiences with their patients.

The Lally et al. study determined that the first days were most important in setting a foundation for success, but that missing one day here and there was okay. Some people were determined to be potentially “habit-resistant,” meaning they found habit formation more elusive despite putting in just as much work as the other participants. 

Some people found habit formation more elusive despite putting in just as much work.

Some psychologists claim that it helps to adopt your chosen new habit while on vacation. Without the normal external cues set by your standard everyday surroundings, the new behavior may stick more quickly. It can help to have internal motivation, like a strong desire for self-improvement, rather than external motivation, like other people telling you your new habit is a good idea. Telling your friends and family about your plan for your new habit, however, is a must. They can help hold you accountable. 

Some neuroscientists claim that it is easier to start doing something new than it is to stop doing something that's already a habit. But if you're looking to end a current bad habit, it can help to replace it with a new habit rather than leaving an empty hole where your bad habit once was. 

If you’re one of the four in ten people who will be making a New Year’s resolution this year, however you go about it, choose something reasonable that you can actually achieve. Start running 10 miles a day starting tomorrow even though you're not an avid runner? Probably not going to happen. Cook a healthy dinner at home one more night per week? You can do that.

At least one study showed that when trying for a new habit, making a resolution makes you ten times more likely to be successful. So go ahead—state your intentions and put your brain to work.

Please note that archive episodes of this podcast may include references to Ask Science. Rights of Albert Einstein are used with permission of The Hebrew University of Jerusalem. Represented exclusively by Greenlight.

About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.