Habit stacking: how to anchor a new habit to something you already do

What anchoring a habit means, and why it might work

“Habit stacking” and “habit chaining” are popular labels. They don't appear under those names in the studies consulted, which talk instead about plans with a routine-based cue, as opposed to a time-based cue, or about where a behavior sits within a routine.¹² In practice it's an “if–then” plan in which the “if” is something you already do: “when I close my laptop, then…”

Why might it work? According to a theoretical model of habits, when a behavior is repeated, it becomes associated with what surrounds it — the place, but also the action that comes before it — until that context is enough to set it in motion.⁷ An article for family doctors turns this into a piece of advice: choose a cue you'll come across and notice every day; a situation in your daily routine, it says, is a convenient and stable starting point.⁶

A routine or a set time?

This is the best-studied comparison. In a trial in Germany, 192 adults chose an eating behavior — drinking water and eating fruit were the most common — and were randomly assigned to tie it to a daily routine (“after breakfast”) or to a time (“at nine o'clock”). For 84 days they recorded whether they did it and to what extent it came without thinking.¹

Both groups progressed in a similar way: there were no differences in how often they followed through or in how automatic the action became. What did matter was repetition: those who did the action every time their cue came up found it more automatic, and that gain was faster at the beginning.¹ How long it took each person is covered in how long it takes to form a habit.

The authors suggest a possible explanation for the tie: perhaps those who chose a time picked, without saying so, a moment when they already tended to do the same thing every day, so the time also worked as a routine.¹ In a survey of 1,244 Australian adults, physical activity that always started after the same routine was associated with it feeling more automatic, and activity that always started at the same time, with doing more of it.⁵ This is an association measured at a single point in time, not proof that one cue is better than the other.

The practical takeaway, as a deduction: choose the cue that really does come up every day in your week. If your schedule changes often, a routine has the advantage of moving with it; the trial's authors note that observational studies pointed in that direction, although their trial didn't confirm it.¹

How to recognize a good anchor

No trials compare anchors one by one. The criteria in this table come from what studies say forms a habit — repeating the action in the same context, after a cue that's easy to detect — and we point out when they are a deduction.

The place criterion ties in with another idea from the guide: setting up your environment so that what you need is where the cue appears. And an anchor can come up several times a day: if you want to get up from your chair more often, the end of each call can work. What's known about breaking up sitting time is covered separately.

Right before or right after?

It's often taken for granted that the new action works better right after the anchor. In an exploratory study with 50 people, half were asked to floss before brushing their teeth and the other half after. Those who flossed after tended to form a stronger habit and, eight months later, had a stronger habit and flossed more often.²

The same researcher tested it again in her doctoral thesis, with 118 people in a 16-week study. This time the full analysis found no differences between before and after, in either frequency or automaticity; in a simpler comparison, the “before” group even gained slightly more automaticity.³ In the thesis she also notes that the first result didn't reach statistical significance at four weeks and that the eight-month result was based on the 29 people, out of 50, who responded.³

Given what's available, the exact position doesn't seem decisive. Our suggestion is to pick whichever fits your routine: if you rush out of the bathroom after brushing, “before” may feel more natural.

Alarms and reminders: they help you follow through, but do less to make it automatic

Many people replace the anchor with a phone alarm. A four-week study compared this indirectly: 133 people had to send a text message every day saying what they had eaten, and 96 completed the four weeks; what was really being studied was whether sending that message became automatic. Some got a reminder in the afternoon; others were asked to send it right after they finished eating; others had no cue at all.⁴

With a reminder they followed through more, but by the end the action felt less automatic to them than to those who tied it to the end of a meal or had no cue; between those two groups there were no significant differences.⁴ The authors, who study app design, suggest using notifications to remind people of the plan (“after you brush your teeth, do…”) and phasing them out over time; it's a proposal they didn't test.⁴

The deduction for everyday life: if you use an alarm at first, have it remind you of the anchor, not take its place.

Why a chain breaks

• The anchor doesn't happen every day. If it only exists on weekdays, on Saturday the action is left without a cue. That's why a daily cue is recommended.⁶
• Your routine changes. In students who transferred to another university, the habits of exercising, reading the newspaper or watching TV held up only when something about the context stayed the same.⁸ Vacations, shift work or a new job can wipe out the anchor; our suggestion is to have another one in mind for those days.
• The first step isn't clear. In a survey of 229 students, how often they did three behaviors was more closely related to the habit of getting started on them than to the habit of going through their steps without thinking.¹⁰ Hence a deduction: right after the anchor, know exactly what you do first.
• The anchor is used to stop doing something. According to the researchers, you can't form a habit of not doing something; they recommend choosing a new action instead of trying to suppress another one.⁶
• Too many links at once. We haven't found studies on long chains of new actions. The prudent thing is to consolidate one before adding the next; in the guide we explain why starting with a single change is a practical option, not a proven rule.

A blank day, on the other hand, doesn't break the chain: we cover this in what happens if you skip a day.

What isn't known yet

Research on anchors is scarce: one trial comparing routine and time, small studies on flossing or phone messages, and a survey or two. Almost everything is measured with questionnaires in which each person rates how automatic the action feels to them, and the results vary a lot from one person to another.¹³ We don't know which kind of anchor suits each behavior or how many new actions can be chained together.

Anchoring a habit is a technique for organizing your day, not a treatment. If you want to make a major change to your physical activity or your diet and you have an illness, take medication or are pregnant, talk to a health professional first.