The Hook Model
Nir Eyal
Trigger → Action → Variable Reward → Investment: the loop that turns products into habits.
What it is
A four-phase cycle for building habit-forming products: an external or internal trigger prompts an action, the action delivers a variable (unpredictable) reward, and the user invests something — data, effort, social capital — that makes the next loop more likely.
How we weaponize it
We audit every product and content flow for loop integrity: Is the trigger timed to a real moment of need? Is the reward variable enough to stay interesting? Does each visit make the product more valuable for the next? Marketing campaigns are designed as loop starters, not one-off blasts.
Out-of-the-box example
For a fitness app, we replaced the ignored daily-reminder push with a 'streak rescue' that only a workout buddy could trigger. Social trigger, variable reward, instant investment — day-30 retention jumped 2.1x without a single new feature.
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