Hooked: How to Build Habit-Forming Products (Summary)
Why do you mindlessly scroll through Instagram, even when you know there's nothing new to see? It's not a lack of willpower; it's by design. The apps you use every day are engineered like slot machines to create an 'itch' in your brain—a negative feeling like boredom or loneliness—that only opening the app can scratch. You're not just using the product; the product is using you.
Your Brain on a Slot Machine
The key to keeping users engaged isn't just rewarding them, but making the rewards unpredictable. Our brains crave novelty, and the variable nature of rewards creates a state of anticipation that is neurologically similar to pulling the lever on a slot machine.
The 'pull-to-refresh' feature on your social media or email app is a perfect example. You pull down, and you might get a juicy new email, a viral tweet, or absolutely nothing. It's this intermittent reinforcement that creates the compulsion to check constantly.
The Goal Is to Scratch an Internal Itch
Initially, users are prompted by external triggers (like a notification or an ad). The ultimate goal for a habit-forming product is to attach itself to an internal trigger—a pre-existing emotion or routine. The product becomes the user's default solution to a feeling.
When you feel a pang of loneliness, your first instinct might be to open Facebook. When you're bored standing in line, you reflexively open Twitter or TikTok. The product has successfully become the go-to balm for an internal emotional state, no external prompt needed.
Users Must Invest to Stay Hooked
The final step of the Hook Model, Investment, is what makes the cycle repeat. By getting users to put something into the product—time, data, effort, or social capital—you increase the likelihood of their return and load the next trigger.
When you post a photo on Instagram, you are making an investment. You're now more likely to return to the app to check for likes and comments (loading the next trigger). By following friends or curating a playlist on Spotify, you are storing value in the platform, making it harder to leave.
The Morality of Manipulation
Eyal proposes a 'Manipulation Matrix' to help builders decide if they should be hooking users. It asks two questions: 'Does the product materially improve the user's life?' and 'Would the creator use it themselves?' The goal is to be a 'Facilitator' of healthy habits, not a 'Peddler' of addictions.
The creator of a fitness app that encourages daily exercise is a 'Facilitator'—they use their own product and believe it helps people. In contrast, the designer of a predatory gambling app might be a 'Peddler'—creating a harmful addiction for profit that they wouldn't wish on themselves.
