- 66 days needed on average: The average time to reach maximum automaticity was 66 days.
- It varies per person, though: The time it took to build maximum automaticity varied greatly between participants from 18 days to a predicted 254 days. This is much longer than most previous estimates of the time taken to acquire a new habit.
- Complex habits take longer: more complex behaviours were found to take longer to become habits. Participants who'd chosen an exercise behavior took about one and a half times as long to reach their automaticity plateau compared with the participants who adopted new eating or drinking behaviors.
- A few omissions are okay: What about the effect of having a day off from the behavior? Writing in 1890, William James said that a behavior must be repeated without omission for it to become a habit. The new results found that a single missed day had little impact on later automaticity gains, either early in the study or later on, suggesting James may have overestimated the effect of a missed repetition. However, there was some evidence that too many missed repeats of the behavior, even if spread out over time, had a cumulative effect, reducing the maximum automaticity level that was ultimately reached.
Lally, P., van Jaarsveld, C., Potts, H., and Wardle, J. (2010). How are habits formed: Modelling habit formation in the real world. European Journal of Social Psychology DOI:10.1002/ejsp.674