Technique · Hooked
Trigger inventory and the session trigger mix
List every external trigger by type (paid, earned, relationship, owned) and form (explicit or implicit), with its opt-in and revocation rates. Tag each session with the trigger that started it, so the share of self-started sessions can be read by tenure.
Plain label: where sessions come fromAlso known as: paid earned relationship owned, external trigger types, explicit and implicit triggers, unprompted sessions, trigger attribution, session source
How it works
The four external trigger types do different jobs: paid, earned and relationship triggers bring people in, owned triggers bring them back until a habit forms, and internal triggers keep them. Without knowing which trigger started each session, a team can't tell whether use is becoming self-started or is being rented through ads and reminders.
Evidence warning
Paying to bring back existing users is a warning sign; the book treats paid triggers as an acquisition tool only.
How to build it
- Web
- Record a trigger_type at session start: UTM and referrer for paid and earned, invite tokens for relationship, notification and email IDs for owned, none otherwise.
- Mobile
- Attribute an app open to a push or deep link received in the prior 30-60 minutes; count the rest as self-started.
- Email and SMS
- Tag every send with an ID that survives the click so sessions from owned triggers can be counted.
- B2B
- Count sessions started from connected tools (chat, calendar) as owned triggers the customer granted.
What can go wrong
- Counting every session after any notification as prompted, which hides internal triggers.
- Changing reminder cadence with no baseline mix.
Pairs well with
- Read the self-started share on the habit horizon, not after a week.
- Run it before testing notification timing against a holdout.
In practice
Where it shows up
Limits
What we don’t claim
- The Hook Model is a practical design tool, not a validated or complete theory of behavior.Hooked, Introduction
Sources
Hooked · Nir Eyal
Ch.2 · Intro
Source IDs: HK-T05HK-TRG02HK-TRG05
Book content is paraphrased, never quoted at length. Last verified October 24, 2026.
Your product
Find the stage your product is stuck in
Gamify It reads your product, picks the one move that matters at its stage, and sizes the test to your traffic. Connecting is free; a Pro subscription starts it.