Repetition, in the same setting, for longer than anyone wants. Programs lift behavior while they run. The setting is what keeps it going after they stop.
A reorder from a habit doesn’t need persuading. The product ran out, so the customer buys more, the way they buy toothpaste. That’s the kind of repeat buying worth building, and the research on how it forms is more useful, and slower, than the popular version.
In two diary studies by Wendy Wood and colleagues, a large share of the everyday behaviors people recorded were habits in the authors’ sense: done almost daily, in the same setting, often while thinking about something else Published. Wood and Dennis Rünger’s review describes how they form: an action repeated in a stable setting gradually becomes linked to that setting, until the setting starts the action on its own. People then tend to explain their habits as choices, which is why customers will tell you they buy you because they love you when part of the reason is that you’re what’s on the shelf Published.
The clearest demonstration involves popcorn. David Neal, Wood and colleagues gave cinema-goers fresh or stale popcorn. People with a strong habit of eating popcorn at the movies ate about as much stale popcorn as fresh; how hungry they were or how much they liked it barely mattered. The habit only ran in the cinema, and only when they ate with their usual hand Published. The setting carried the behavior. Change the setting, and people went back to deciding.
The setting does the remembering. Design for the setting.
The number that gets repeated is 21 days. The best study says otherwise. Phillippa Lally and colleagues had 96 volunteers repeat a new eating, drinking or exercise behavior daily in the same setting for 12 weeks. For the people whose data fit their model, the median time to reach 95% of their eventual automaticity was 66 days, and individual estimates ran from 18 to 254 days Published. The study ran 84 days, so the longest estimates are projections Derived. The authors also found that missing a single day “did not materially affect the habit formation process” Published.
Two things follow for a brand. The cue and the education have to last two to three months, not one welcome series. And your messages should say plainly that a missed day doesn’t reset anything, because customers who think they’ve failed stop.
The largest test of this was a megastudy led by Katherine Milkman, in which 30 scientists designed 54 different four-week programs to get 61,293 members of a US gym chain to work out more Published.
Nearly half the programs worked while they ran. Very few left a lasting change. The most effective program paid small rewards for coming back after a missed workout Published. That’s a useful design rule for any brand: the moment that matters most isn’t the first use, it’s the return after the first gap.
Bas Verplanken and Wood point out that habits are most open to change when life changes: a move, a new job. The old cues disappear, and new ones haven’t formed Published. That cuts both ways. It’s the best time to win a customer from a competitor’s habit. It’s also when you lose your own. When a customer changes their shipping address, their bathroom shelf just moved. That’s the moment to send the first move again.
This is one chapter of Used, Not Bought, which is free and readable in full on a single page with no form in front of it.