No, it doesn’t take 21 days to form a new habit. A new study shows why: ScienceAlert

In 1960, a plastic surgeon by the name of Maxwell Maltz published a hugely popular book that spawned a false factoid – it only takes 21 days to change your habits and form a new habit.

This figure was based on Maltz’s observations of how long it took his patients to adapt to their new faces. While it has little to do with changing behaviors, many of us still cling to the promise that within weeks we can make small but impactful changes to our daily lives.

Now, scientists from Caltech, the University of Chicago and the University of Pennsylvania have challenged that already dubious idea using data from more than 30,000 gym goers who trained around 12 million times over a period of time. four years, and more than 3,000 hospital workers who collectively washed their hands 40 million times over nearly 100 shifts.

Using machine learning tools to analyze when people’s behaviors became predictable – and therefore habitual – researchers have found that (perhaps unsurprisingly) some habits take longer to form than others. Getting into the training rhythm takes an average of about six months, for example.

“Contrary to popular belief that it takes a ‘magic number’ of days to form a habit, we find that it typically takes months to form the habit of going to the gym, but weeks to form the habit. to wash their hands in the hospital”, to write the team of behavioral scientists, led by Colin Camerer at the California Institute of Technology (Caltech).

Trying to understand habits – how to create them and how to break them – perpetually interests psychologists for obvious reasons. Habits, whether good or bad, can have a huge impact on our health and well-being: simple habits can relieve mental fatigue to make a bazillion tiny decisions in a day; lives beset by addiction can quickly crumble.

Despite the attention, this new research is one of the few studies that has looked at how quickly people form habits in real-world settings, outside of the artificial realm of psychology labs.

A landmark study of 2009 found that it took people about two months to establish a habit tied to a daily cue, such as eating breakfast. But there was huge variation among the 96 volunteers: It took between 18 and 254 days for people to feel like their new habit had become automatic.

Those studies, however, relied on people filling out surveys to report their behaviors, while this new study analyzed point data on gym visits and handwashing practices to see when real, repeated behaviors became predictable.

Just as gym members had to slip in when they arrived, staff involved in a separate study monitoring handwashing in hospitals had to scan an ID card each time they washed their hands. The data included details that allowed researchers to study certain variables, such as time of day or day of week, to determine if this had an effect on an individual’s behavior.

“With machine learning, we can observe hundreds of context variables that can be predictive of behavioral execution,” explain Behavioral scientist Anastasia Buyalskaya, who now works for a French marketing company after completing her graduate studies at Caltech.

If more time had passed since their last visit to the gym, gym-goers were less likely to return, but the time of day had little bearing on people’s usual attendance. As with previous research, it appears that keep some flexibility in an exercise routine is important, but so is consistency.

Two-thirds of gym-goers stuck to the same days of the week, with Mondays and Tuesdays being popular – and again, this echoes other studies suggesting motivation peaks around so-called fresh start dates.

As for sticking to their new exercise habit, it took between four and seven months, the modeling suggests, which is more than double what previous studies had found. On the other hand, it was only a matter of weeks before health workers started washing their hands regularly.

This shows that forming a new habit really depends on the person, but also on the behavior itself, the time and effort required, and the cue that triggers it.

Some people might take this to the extreme, sleeping in their running clothes to eliminate any “friction” when exercising in the morning as planned. But for most of us, with time and repetition, habits are formed slowly – if we can find the right motivation.

The study was published in PNAS.

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