Implementation intentions: the if-then sentence that does the work

An implementation intention is a sentence with a fixed shape: if situation X arises, then I will do behaviour Y. Gollwitzer proposed it in the 1990s, and the meta-analysis that followed covered several hundred studies with a medium effect size. In behaviour research that is a strong result, and unusually for this field it has held up.

The mechanism is not motivation. It is that you move the decision from the moment of action to a quiet moment beforehand, and you attach the behaviour to a concrete environmental trigger rather than an intention. “I will exercise more” has no trigger. “If it is Tuesday at 18:00, then I will put my running shoes on and leave the flat” has one, and your brain can spot it without deliberation.

What makes this worth a whole page rather than a tweet is the failure modes. Vague triggers do nothing. Triggers you rarely encounter do nothing. Stacking three intentions on the same trigger does less than one. And the effect shrinks when the behaviour itself is unpleasant enough that you would refuse it even with a perfect cue.

This guide covers how to write one that works, twelve worked examples across common habits, and how to encode the trigger into a tracker so the app reminds you of the if rather than the then.

Outline

Status: outline. The introduction above is finished copy. Everything below is the section plan for the full draft, targeted at about 1 600 words.

1. The shape of the sentence. If plus situation, then plus behaviour, and why both halves must be concrete.
2. What the evidence actually shows. Effect sizes, where they are largest, and where they vanish.
3. Writing a trigger you will actually meet. Frequency, specificity, and the location test.
4. Twelve worked examples. Reading, exercise, water, medication, saving, phone use, and six more.
5. Coping intentions. The second sentence, for the situation that usually stops you.
6. Encoding it in a tracker. Putting the if in the habit name and the reminder on the trigger, not the clock.
7. Where it fails. Unpleasant behaviours, competing intentions, and over-stacked triggers.