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Concept

Hook Model

Also known as: Trigger-Action-Reward-Investment

habit-forming-products product-design framework

A four-stage framework, developed by Nir Eyal from decades-old research on operant conditioning, describing how habit-forming products (Facebook, Instagram, games) hook users into repeated, eventually self-initiated use.

  1. Trigger — either external (a ping, ding, or notification from outside) or internal (an uncomfortable emotional state — boredom, loneliness, uncertainty — that the product promises to relieve). Eyal argues all motivation is ultimately about escaping discomfort rather than pursuing pleasure, so the internal trigger is the real driver. External triggers work best when timed to match a context the user is actually in — sending a notification on the product's schedule rather than the user's reads as spam (Eyal's example: a flight attendant waking a sleeping passenger to ask if he wants a drink).
  2. Action — the simplest possible behavior done in anticipation of a reward (scrolling a feed, pressing play).
  3. Variable Reward — the reward isn't guaranteed every time, which increases engagement rather than reducing it (see Variable Reward Schedule).
  4. Investment — the user puts something into the product (data, content, followers, reputation) that improves the product with use and loads the next trigger, and which people value more because they made it themselves (see IKEA Effect, LinkedIn Investment Study).

Repeated cycles through all four stages eventually shift the user from needing an external trigger to being self-triggered internally — the point at which a product becomes genuinely habit-forming, and hard for a competitor to displace even if objectively better (the QWERTY keyboard, though provably inferior to alternatives, persists purely on habit lock-in). Removing a product's friction/pain point, even a small one, can be as effective as adding features: an 8-millisecond slowdown in Google search cost 10 million searches, and a 1-second checkout delay cost Walmart 2% of purchases (see Product Speed and Pain Threshold Studies).

Discussed in

  • Episode 13 — 13- What makes products like Instagram so addictive

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