In a series of articles over the next six weeks, I’ll be discussing how to better understand and change behaviour at scale. In the first of these articles, I explore a key question — How do we successfully build a new habit?
One of my favourite studies published over the past year utilised machine learning to investigate how long it takes to form a habit. The main finding of this study may be surprising to some — there is no magic length of time it takes to form a habit. Beneath this headline are important implications which can help researchers and practitioners develop and implement programmes which are more likely to be effective over the long-term.
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There is no magic number
This study was conducted by six social scientists — based in California Institute of Technology, University of Chicago, and Wharton. One of the study’s authors, Katherine Milkman says
“There’s this widely spread rumour that it takes 21 days to form a habit. You may have also heard it takes 90 days to form a habit. There are popular books that tout these numbers that don’t have a sound basis in research. What we find is there is no such magic number”.
The researchers developed a machine learning algorithm to analyse millions of data points tracking two behaviours: gym attendance and hand sanitising. The study’s methodology, which analysed real-life data rather than relying on self-reported measures, provides a more accurate picture of habit formation.
The study tracked more than 30,000 gym goers, and more than 5,000 healthcare workers from 30 hospitals. The researchers analysed over 12 million gym sessions and more than 40 million hospital hand washing procedures over the course of a year.
The researchers said they could be confident that it took ‘weeks’ to develop a habit, although given how habit formation varies from person to person, they couldn’t provide a more specific timeframe. As a result, the researchers suggest we are better off focussing on three things, as opposed to time:
How complex is the behaviour?
How often is it being repeated?
What is the nature of the reward for the behaviour?
The study highlighted another important finding — gym goers who had already formed a habit were less responsive to incentives and rewards. Whereas people who had not yet formed a habit were more likely to increase their attendance if offered a new incentive (such as a financial reward). This tells us that when designing new solutions for people to start a new habit incentives or rewards can help. Although we should ease off these external prompts and incentives as habits are formed and people become more intrinsically motivated.
Where did the 21-day habit myth come from?
The ‘21-day rule’ is a common belief that it takes 21 days to form a new habit. However, this is a simplified and somewhat misleading notion. The actual time it takes to form a habit can vary widely from person to person and from habit to habit. The idea of the ‘21-day rule’ for habit formation is often attributed to Dr. Maxwell Maltz, a plastic surgeon and author. In 1960, Dr. Maltz published a book called “Psycho-Cybernetics” in which he discussed his observations regarding behaviour change in his patients. Dr Maltz wrote:
“It usually requires a minimum of about 21 days to effect any perceptible change in a mental image. Following plastic surgery it takes about 21 days for the average patient to get used to his new face. When an arm or leg is amputated the “phantom limb” persists for about 21 days. People must live in a new house for about three weeks before it begins to “seem like home”. These, and many other commonly observed phenomena tend to show that it requires a minimum of about 21 days for an old mental image to dissolve and a new one to jell.” (pp xiii-xiv)
Since then, various theories and studies have been published which aim to attach a new ‘magic number’ to the formation of habits. In 2021, psychologists suggested that it took a median of 59 days to form a habit.
However, new research with ground-breaking techniques is shattering the idea that a new habit can be formed with a magic number of days. The time taken to form a new habit can vary between under a month, to over half a year, depending on the individual and the behaviour. A hospital director could embed regular hand washing among healthcare workers in as little as 2–3 weeks. Whereas a workplace wellbeing scheme aimed at encouraging employees to exercise regularly, is likely to take several months.
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Focus on the purpose, not the number
The latest research tells us that it’s unwise to attempt to assign a number to the formation of a new habit. Embedding a new habit is likely to depend on the person and the behaviour. For a habit to stick, a person must continue a new behaviour consistently. And to achieve this, it’s better to attach a new behaviour with people or a purpose the person cares about.
Experts say that the best way to form a new habit is to attach it to an existing one. For example, if you enjoy getting a coffee with friends and want to walk more, combine the two. Habit stacking is about looking at your daily patterns (i.e., brushing your teeth, checking emails, or making your morning coffee) and weaving in new habits to accompany your daily routine.
There are 3 key actions we can take to help new habits stick. Along with stacking new habits with existing ones, we should:
Start small and build slowly — Making a substantial change to the way we live our lives requires a high level of motivation. Starting small can help us build momentum. For example, a short walk can build towards an active lifestyle.
Make it easy — By removing any friction or barriers which can get in the way of our new behaviour, we are much more likely to stick to it. For example, by preparing healthy meals or getting our gym kit out in advance. On the other hand, adding friction can help us get rid of bad habits. For instance, putting your phone away in a separate room as you start your day can help boost productivity.
Reward new behaviours — Positive reinforcement helps to reframe how we perceive a new behaviour, and this helps it stick. For example, listening to your favourite music or podcast whilst taking part in a new behaviour can help build the motivation to continue.
The takeaway
The truth is, there is no magic number when it comes to forming a new habit. The speed of habit formation differs according to the behaviour in question and a variety of other factors — such as individual characteristics and the reward for the new behaviour. The best way to build a new habit is to start small, make it convenient and reward new behaviours. We are more likely to build a long-term habit if the new behaviour aligns with the people and purposes we care about.
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Sources:
Buyalskaya, A., Ho, H., Milkman, K. L., Li, X., Duckworth, A. L., & Camerer, C. (2023). What can machine learning teach us about habit formation? Evidence from exercise and hygiene. Proceedings of the National Academy of Sciences, 120(17), e2216115120.
Busting the 21 days habit formation myth. Available at: ttps://blogs.ucl.ac.uk/bsh/2012/06/29/busting-the-21-days-habit-formation-myth/#:~:text=21%20days%20is%20a%20myth,you%20are%20trying%20to%20do
Keller, J., Kwasnicka, D., Klaiber, P., Sichert, L., Lally, P., & Fleig, L. (2021). Habit formation following routine‐based versus time‐based cue planning: A randomized controlled trial. British Journal of Health Psychology, 26(3), 807–824.
New Scientific Evidence Points To Wide Discrepancies In The Time You Need To Build Habits. Available at: https://www.forbes.com/sites/hecparis/2023/06/08/new-scientific-evidence-points-to-wide-discrepancies-in-the-time-you-need-to-build-habits/
How to Build Healthy Habits. Available at: https://www.nytimes.com/2020/02/18/well/mind/how-to-build-healthy-habits.html#:~:text=The%20best%20way%20to%20form,stack%20on%20a%20new%20habit.
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