Variable Reward 

- Triggers cue the user to take action and are the first step in the Hook Model.

- Triggers come in two types: external and internal.

- External triggers tell the user what to do next by placing information within the user's environment.

- Internal triggers tell the user what to do next through associations stored in the user's memory.

- Negative emotions frequently serve as internal triggers.

- To build a habit-forming product, makers need to understand which user emotions may be tied to internal triggers and know how to leverage external triggers to drive the user to action.