How habits form

A habit is a behaviour triggered automatically by a situation, without much conscious thought. Brushing your teeth before bed, reaching for your phone when you wake up, or taking the same route to work are all habits.

Habits are efficient. By automating routine actions, the brain frees up attention for other things. The downside is that unwanted habits run just as automatically as helpful ones.

Researchers often describe habits as a loop. A cue, such as a time, place, emotion or preceding action, triggers a routine, the behaviour itself, which is followed by a reward that makes the loop more likely to repeat.

With repetition, the brain links the cue directly to the routine. Studies in animals show that as a behaviour becomes habitual, control shifts toward brain regions called the basal ganglia, and the behaviour continues even when the reward is removed.

A popular claim says habits take 21 days to form, but that figure has little scientific basis. A study led by Benjamin Lally at University College London, published in 2009, tracked volunteers as they tried to form new daily habits such as drinking water with lunch or going for a run.

In the Lally study, reaching the point where a behaviour felt automatic took anywhere from 18 to 254 days, with a median of about 66 days. Simpler behaviours became automatic faster, and missing a single day did not significantly derail the process.

• Start small: tiny behaviours, like doing two push-ups, are easier to repeat consistently.
• Attach new habits to existing ones: after I pour my morning coffee, I will write my to-do list.
• Keep the cue and context stable, since habits form most strongly in consistent situations.
• Make the behaviour easy by reducing friction, such as laying out exercise clothes the night before.
• Make it rewarding, so the brain has a reason to repeat it.

Willpower alone is often a poor tool against habits, because habits are triggered automatically. Research by the psychologist Wendy Wood suggests that people who seem to have strong self-control often rely less on resisting temptation and more on arranging their environment so temptation rarely arises.

Useful strategies include removing or avoiding cues, such as keeping snacks out of sight or leaving a phone in another room; adding friction to the unwanted behaviour; and replacing the routine with a different one that delivers a similar reward. Life changes, such as moving house or starting a new job, disrupt old cues and can be good moments to change habits.

Habits accumulate. Small daily behaviours, repeated over months and years, have large effects on health, finances, skills and relationships.

Some writers suggest framing habits in terms of identity, for example thinking of oneself as a person who exercises, rather than someone trying to exercise. Whatever the framing, the evidence points to the same practical lesson: consistency in a stable context matters more than intensity.