Book Review: Hooked by Nir Eyal with Ryan Hoover

Reading Hooked by Nir Eyal and Ryan Hoover was a joy over the past couple weeks. Overall, the book is logically developed and is easy to follow with clever jokes dispersed throughout. As the name suggests, the book proposes the hook framework to explain the mechanism of building a habit-forming product. Before diving into the hook model, the book throws an interesting question: should start-ups create vitamins or painkillers? According to Eyal, painkillers solve an obvious need. By contrast, Vitamins do not necessarily relieve an obvious pain point but appeal to users’ emotional rather than functional needs. When it comes to initial financing, companies who build painkillers seem to be more successful. Of course, for a product to last, it needs to be both. Many products begin as vitamins, such as the early-stage Facebook restrained to Harvard. Over time, as habits form, they become painkillers as they provide ongoing pain remedies. For example, as Facebook greets the world, it became the go-to solution when people need to feel connected to a community.

Trigger: the actuator of behavior

A trigger can be external or internal. An external trigger usually contains information telling the user what to do next. For example, an arrow-shaped button with text “log in” is a common external trigger asking people to log in.  In contrast, the internal trigger is the association stored in one’s memory. For example, many Instagram and Snapchat users over time likely associate the need to capture interesting things with the app on mobile devices. Successful products like these help users to create a subconscious link between the product and the internal trigger. Negative emotions are especially powerful internal triggers and have a significant impact on people’s daily routine. The need to relieve oneself from boredom, loneliness, frustration, confusion, and indecisiveness almost immediately prompt a subconscious action.

The key to leverage internal trigger is to understand how users truly feel. A pitfall in product designing is that researchers tend to focus on what they wish people to do (produce cinema-quality home videos) instead of what people actually do (watching cat videos online). A way to ensure a good understanding of user narrative is 5 Whys Method—repeating why five times to find out why one uses a product.

Action: the simplest behavior in anticipation of reward

Eyal draws insights from the Fogg Behavior Model B = MAT: for a user to take action, the user must have sufficient Motivation, the Ability to perform the desired action, and a Trigger present to activate the behavior. Ranked by cost-effectiveness, making sure a clear trigger is present comes first, increasing the ability to complete the action is the next while aligning with the right motivator comes last. To increase a user’s ability to act is to reduce the effort needed. Product designers can improve ability by decreasing 6 key factors: time, money, physical effort, brain cycles, social deviance, and non-routines. Indeed, easier is better. Many websites use “sign up with Facebook” to simplify the sign-up process and to ultimately increase user base.

A caveat is that designers must also keep Heuristics in mind, which are cognitive shortcuts people take when making quick decisions and can skew people’s perceptions. Few noteworthy ones are the scarcity effect—less quantity = higher quality, the framing effect—price positively correlates to perceived value, the anchoring effect—people often anchor to one price when making decisions, and the endowed progress effect—motivation increases as people believe they are nearing a goal.

Variable rewards: unpredictable, different every time

When someone posts a picture on Facebook, he or she does not know how people are going to react, and for every picture posted on one’s Facebook, the response from the community will be different. Human brains are most excited not when receiving a reward but in anticipation of it. The less predictable the reward is, the more exciting the anticipation is. There are three types of variable rewards. Rewards of the tribe is the search for social validation and connectedness with other people. Facebook and Stack Overflow are prominent examples. Rewards of the hunt is the search for material resources and information. The pursuit of material gain makes gambling machines enticing while the abundant information on Twitter makes it a social staple. Rewards of the self is the search for intrinsic rewards of mastery, competence, and completion. Many people check email multiple times to make sure they stay on top of everything.

It is important for product designers to respect user’s autonomy. If a product is outside the routine of the targeted demographics, it is making users do what it wants, rather than helping users to do what they want. Such product is likely to meet immediate resistance.

Investment: the anticipation of rewards in the future

Investments in a product create preferences because people tend to overvalue their work, be consistent with past decisions and avoid cognitive dissonance. For a user to invest in a product is to store values, including content, data, followers, reputation, and skill. A strategy to facilitate the process is to progressively stage the investment into small chunks of work. A successful product should take in users’ investment and give out the next trigger. Notifications of curated content by social media platform or reminders by productivity apps are examples.

Manipulation Matrix

Eyal offers a manipulation matrix for designers to self-reflect

Materially improves the user’s life Peddler Facilitator
Does not improve the user’s life Dealer Entertainer
  The maker does not use it The maker uses it

The most undisputed scenario is the facilitator which improves user’s life, and the maker uses it. The entertainer, such as Angry Birds, may be addicting but there is little intention to manipulate users into habitual use of the product. The peddler is made with good intention, but the maker may be distant from the experience of a typical user, such as fitness apps. The product designers need to distinguish what they think the need is versus users’ real need. At worst the product will be unhelpful, but there is little ethical concern.

The dealer is ethically uncertain. In the absence of usefulness and authenticity, the only reason the designer wants to hook users presumably is to exploit them for monetary gain. Currently, the responsibility of reasonable use of digital products lies on the users. Eyal proposes that in the future, the product itself should alert users whether they are using it too frequently or for too long.


I recommend this book to anyone who is interested in product design, especially entrepreneurs. What I liked most about the book is that it offers actionable items at the end of each chapter for readers to apply the framework in real-world practice right away. These actionable items are usually in forms of questions to inspire product designers or for designers to take them to their users. I think this book provides a holistic but also nuanced understanding of product design. At the end of the book, it presents a case study on the Bible app to demonstrate the Hook framework, which is a nice way to help readers review and understand the principles discussed in the book.

I wish I could hear more about internal triggers. I agree with the author that an effective trigger ultimately targets emotional stimuli, but I am curious how does social media differentiate themselves then when they seem to target similar emotional response? Facebook, Instagram, and Snapchat all seem to create a sense of connectedness, and all three alleviates the pain of boredom and loneliness. Or, do these mainstream social media, in fact, target different emotional needs?


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