Stacking can make the adoption of new habits easier

In evidence that stacking works, consider dental floss. Many of us clean our teeth regularly but fail to floss. To test whether stacking increases flossing, researchers gave fifty British participants, who flossed on average only 1.5 times per month, information to encourage them to do it more regularly.

Half of the participants were told to floss before they brushed at night, and half after they brushed. Note that only half of the participants were really stacking - using an existing automated response (brushing their teeth) as a cue for a new behavior (flossing). The other half, who first flossed and then brushed, had to remember, oh, yes, first I need to floss, before I brush. No automated cue.

Night one, the reminder works.

Week four, motivation is still feeling useful.

Month eight is where the design gets judged.

The participants who flossed after brushing retained more of the habit because brushing already owned a reliable moment. The toothbrush finished and supplied the cue. Those told to floss first had to remember an additional beginning before reaching the automatic behaviour.

Habit stacking is almost insultingly mundane. It does not promise a new identity, only an address: after coffee, before the shower, when the laptop closes, beside the tablets already taken each morning. The existing sequence removes one decision from a behaviour that would otherwise need fresh permission.

This exposes the vanity in motivational advice. “Want it more” makes failure a character defect. Often the person wanted it perfectly well at breakfast and had no cue left by bedtime. Desire had nowhere specific to report.

The anchor must be stable and the addition small. A kettle can cue two minutes of stretching; it cannot plausibly carry “write a novel”. If the old habit disappears on weekends, the new one disappears with it.

Eight months later, reminders are irrelevant. The useful evidence is boring: brushing ends, flossing follows, and nobody conducts a small motivational summit in the bathroom. If it still depends on a phone alert, move the floss, shrink the action or choose a more reliable cue. The sequence should be visible in what happens, not in how strongly somebody claims to want it.