Apr 17th 2025|3 min read
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Did you make any resolutions this new year? If you did, are you keeping to them? Well done if you are. Polling in America suggests half of new-year resolvers give up by the end of March. More rigorous scientific studies confirm that it takes months for a new behaviour to stick, regardless of when you start.
Habitual behaviour emerges in response to dopamine, a chemical associated with pleasure, being produced as a consequence of a certain action. Two brain systems are involved. One, in the basal ganglia (a set of structures deep in the brain’s interior), responds automatically and predictably to certain stimuli. For example, your morning alarm is a stimulus that activates your “getting up” habit. This will include sub-habits such as “shower”, “make coffee”, “get dressed”, “drive to office” and so on, each with their own triggering stimuli and dopamine reward.
The other brain system, which is goal-directed, is located in the cortex, that organ’s outer layer. Its dopamine reward comes from a deliberate action being successfully performed. This goal-directed system can, if necessary, override the stimulus-response one. For example, if the radio tells you of a traffic problem, the “drive to office” sub-routine will need conscious modification.
For one-off modifications of habits, this arrangement of routine and override works well. But permanent changes, such as either breaking an old habit or making a new one, are thought to require weakening the stimulus-driven system to reduce the pertinence of old stimuli and strengthening the goal-directed one to increase that of new ones.
In a paper published in January, Eike Buabang and his colleagues at Trinity College, Dublin, review the evidence behind various ways in which this can be done. In practice, most proven approaches seem to operate on the stimulus-response side of the equation. Deliberate repetition, that stalwart of hopeful resolution-makers, trains the brain so that what was once goal-directed becomes automatic. In the case of driving to work, the incentive to do this is strong (you won’t get paid otherwise). For things more easily abandoned, reinforcement with small rewards (whether the kick of having lost another kilo at your weekly weigh-in or the praise generated by language-learning or fitness apps) works similarly. To break an unwanted habit, on the other hand, consider removing familiar stimuli. Moving house is known to help—though calling in the removal vans is a drastic approach to resolution-keeping.
Why people learn bad habits in the first place remains mysterious. Most habits form precisely because they are helpful. Automatic behaviours, such as those involved in a morning routine, reduce cognitive load and free mental resources for other tasks, such as working out what to say in the ten-o’clock meeting. But these mechanisms can be subverted. The nicotine inhaled by smoking tobacco—a type of habit so powerful that it has a special name, “addiction”—stimulates dopamine production directly. This is something natural selection could not have foreseen. Non-addictive habits like procrastination are harder to explain.
In the end, though, all this science continues to support the idea that, when it comes to habit-formation, good old-fashioned willpower is the way forward. As the old joke has it: “How many psychoanalysts does it take to change a light bulb? Only one, but the light bulb has to really want to change.” ■
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This article appeared in the Science & technology section of the print edition under the headline “How can you break a bad habit?”
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