January 21st, 2011

New Year’s Resolutions and the Myth of 21 Days

By Kyle Morich

We’re 21 days into the New Year: how are your new habits going?

I felt compelled, like many of us, to come up with a list of resolutions for the New Year.  Some I’ve done well with (enjoying more quality leisure time) and others have been completely ignored (spending less time during the day browsing the web).  Numerous publications and commercial blogs (Lifehacker, for instance) got a lot of mileage in the first few days of 2011 on articles discussing good and bad habits and how to change them.  One of the more frequent pieces of advice alluded to the “21 Day Habit Theory.”  If you aren’t familiar with the concept, it originated with Maxwell Maltz’s 1971 self-help book Pscho-Cybernetics that suggested the brain needs 21 straight days of a behavior to make the proper neural connections that allow habits to form.  The idea has stuck around because A) it was a popular book, selling over 1 million copies and B) because it SEEMS right.

The tricky part about studying unconscious behavior is that you can’t ask people about it.  This seems obvious, but when the majority of our methods for examining the behavior of others are through verbal and conscious methods (e.g., surveys and interviews) we tend to forget that the part of the brain we’re examining has no idea what the unconscious mind is doing or perceiving.  We can only look back and apply post-hoc rationalization to our actions.  This is where the 21-Day rule succeeds.  If you keep failing at creating a new habit, I can tell you that you are failing because you haven’t done it 21 days in a row.  If it becomes a habit, you forget that it’s a problem and stop counting the days.

I’m being unnecessarily harsh to Maltz and his concept here because I want to emphasize one point: there is no conclusive scientific evidence supporting the 21-Day theory, or any other projection of how often a behavior must be performed to become a habit.  Habit formation is a physical process in the brain where the behavior shifts from an Action-Outcome behavior to a Stimulus-Response behavior.  Habits are dependent on many factors: a stable context, the complexity of the behavior, an associated cue for the behavior, how reinforcing the behavior is, etc.  The notion that if everyday I eat a cup of yogurt for breakfast and then juggle knives on a unicycle into oncoming traffic for 21 days straight both will become habitual is absurd.  It also diminishes how difficult it is to form good, healthy life habits and eliminate unhealthy ones.  Eating right and exercising takes a lot of effort beyond simple repetition. Rejecting this theory also puts my business in a tricky situation.  I can’t tell you how many clients have asked, “Okay, how many times does my customer need to buy my product until it’s a habit?” It would be fantastically easy to just say “21” and then cash his check.

This leads me to a wonderful study conducted by a team of researchers led by Phillippa Lally at the University College London in 2009.  Lally and her associates conducted one of the first rigorous studies on habit formation, following 96 volunteers over the course of 12 weeks performing a variety of simple behaviors performed in the same context each day. Lally and team asked the participants to choose a healthy eating, drinking or exercise behavior they would like to make habitual.  The only requirement was that the behavior was not one they already did, could be associated with a cue, and the cue only occurred once per day (one such example was ‘eating a piece of fruit with lunch’). They were then asked to perform the behavior every day for 84 days.  They were also to take a short survey about the previous day’s activity and fill out a Self-Report Habit Index, a questionnaire that ascertains how habitual a behavior has become and assigns an ‘automaticity score’ to that person.

Lally’s team plotted these daily automaticity scores to see if there was a generalized “habit curve” that would emerge from the data.  What they found confirmed an early hypothesis that habit formation follows an asymptotic curve (a curve that slowly decreases in height until leveling off into a plateau).

Asymptotic Curve of Habit Formation

They more often participants performed a behavior, the quicker these curves leveled off.  But peak habituation for individuals varied greatly from 18 to 254 days (they kept collecting data after the study had officially ended). While Lally and her team could not draw any conclusions on the number of repetitions need to reach peak habituation, they were confident that establishing a context and cue for a behavior and repeating that behavior multiple times were the most important factors for an individual to form a habit.

So the 21-Day theory is wrong, but it’s not deleteriously wrong.  Suggesting someone perform a behavior repeatedly for 21 days will help move them along their asymptotic curve of habituation faster, provided the behavior is part of stable context and linked to a cue.  It may not be a habit after those 21 days, but it will be further along than it was three weeks ago.

If your resolutions aren’t going so well, take a look at the behavior you want to implement.  Have you identified a context and cue for the behavior?  Is your resolution too broad and not linked to a specific action? I’d love to hear how you’re handling the yearly struggle of changing personal behavior.

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