Triggers: From External to Internal

Every hook starts with a trigger. External triggers live in the environment and carry explicit instructions: a push notification, an email, an app icon, a friend's recommendation. They're how new products get their first cycles, and they're expensive, you have to keep paying for them in money or attention.

Internal triggers live inside the user. An emotion or situation fires and the product comes to mind automatically: bored, open the feed; lonely, check messages; uncertain, search. Negative emotions are especially potent triggers, and there's no notification involved.

The whole trajectory of a habit-forming product is migration from external to internal. Instagram's early users responded to notifications; mature users open the app the instant they feel the itch of a moment worth capturing or a dull minute in line. When the product becomes the default answer to a feeling, the habit has landed.