Hooked by Nir Eyal [Book Summary & PDF]

Why do some products capture widespread attention while others flop? What makes us engage with certain products out of sheer habit? Is there a pattern underlying how technologies hook us? Hooked breaks down the 4-step Hook Model, discusses the morality of manipulation and uncovers opportunities for innovation.





Who is this book for?

This playbook is ideal for businesses that build products that require ongoing, unprompted user engagement, and therefore need to build user habits within the product to thrive. It is a perfect read for startup founders, visionaries, innovators, but also established corporations who aim to understand how products influence our behavior and use habits for good.

About the author

Nir Eyal has distilled years of research, consulting and practical experience, has taught at the Stanford Graduate School of Business and Hasso Plattner Institute of Design, and his writing on technology, psychology, and business appears in the Harvard Business Review, The Atlantic, TechCrunch, and Psychology Today. He blogs regularly at nirandfar.com.

In this summary

Why do some products capture widespread attention while others flop? What makes us engage with certain products out of sheer habit? Is there a pattern underlying how technologies hook us? Hooked breaks down the 4-step Hook Model, discusses the morality of manipulation and uncovers opportunities for innovation.



We’re hooked! Most smartphone owners check their phone within 15 minutes of waking up. Such an automatic behaviour, done with little or no conscious effort, is called a habit. Habitual actions include brushing your teeth – or checking with Google when you have a question. Our world is becoming a habit-forming place, mainly due to 3 factors:

  1. The increased online connectivity
  2. The ability to collect, mine, and process customer data
  3. The faster & more reliable Internet connection speed

Companies that create strong customer habits gain a significant advantage against their competition, as well as other business benefits:

  • Higher Customer Lifetime Value (customers stay around longer)
  • Pricing plasticity (users become dependent and less price-sensitive)
  • Increased usage (people use the product or app multiple times a day)
  • Reduced promotion costs (users return to the product on their own)
  • Viral growth (a happy customer/user is likely to spark word-of-mouth) Habits can only be formed inside the Habit Zone, where a behaviour occurs with frequency and a high degree of perceived utility.

To provide a deeper understanding of how certain products get us hooked, the author has created the Hook Model, a four-phase process companies use to forms habits through the services we use daily. The 4 phases of this model are:

  1. Trigger
  2. Action
  3. Variable Reward
  4. Investment

The Hook Model describes an experience designed to connect the user's problem to a solution frequently enough to form a habit. In the next chapters, we’ll break down this model, as well as the ethics and opportunities around it.


This is the first step of the Hook Model. Triggers move the user to take action. They come in two types: external & internal.

External triggers

They tell the user what to do next by placing information within the user’s environment. There are 4 types of external triggers:

  1. Paid Triggers (advertising through various channels, mainly used to acquire new users)
  2. Earned Triggers (press mentions and features, usually acquired through media relations built overtime)
  3. Relationship Triggers (the audience sharing the benefit of the product with others – virality, in one word)
  4. Owned Triggers (newsletters and notifications that the user has opted in to receive)

Owned triggers are the most important ones because they occur more often and prompt repeat engagement until a habit is formed.

Internal Triggers

They tell the user what to do next through associations stored in the user’s mind. Products coupled with negative emotions (boredom, loneliness, frustration, confusion, indecisiveness), thoughts, or pre-existing routines usually leverage internal triggers.

To scratch the nagging itch that negative emotion brings, we resort mindlessly to the top-of-mind solution: googling is a click away every time we feel unsure or logging on Facebook promises validation every time we feel alone. To build better habit-forming products, companies need to understand deeply their users’ behaviours, needs, fears, and desires.

As Evan Williams (Twitter, Medium) said:

“We often think the Internet enables you to do new things… But people just want to do the same things they’ve always done.”

Actionable Takeaways

Who is your product’s user? Come up with 3 internal triggers that could cue your user to action (emotions, thoughts, or routines). Finish this brief narrative: “Every time the user (internal trigger), he/she (first action of intended habit).”

How can you couple an external trigger as closely as possible to when the user’s internal trigger fires? Think of at least 3 conventional ways to trigger your user with current technology (emails, notifications, text messages, etc.)


This is the second step of the Hook Model. If the user doesn’t take action, the trigger is useless.bThe action is doing something with little or no barriers, in anticipation of a reward. According to Dr. BJ Fogg’s Behavior Model:

“For any behaviour to occur, a trigger must be present at the same time as the user has sufficient ​ability​ and ​motivation​ to take action.”

Motivation = the level of desire to take that action. Ability = the number of obstacles that stand in the user’s way

To increase the motivation of the user to take action, keep in mind the 3 Core Motivators. All humans seek pleasure to avoid pain, seek hope to avoid fear and seek social acceptance to avoid rejection.

To increase the ability of the user, consider the 6 factors of simplicity:

  1. Is the user short on time? (Time)
  2. Is the behaviour too expensive? (Money)
  3. Is the action too labour-intensive? (Physical Effort)
  4. Is the product too difficult to understand? (Brain Cycles)
  5. Is the action perceived as socially inappropriate? (Social Deviance)
  6. Is the action outside of the user’s normal routine? (Non-Routineness)

In the question “should I increase first the motivation or the ability?” the author answers “always start with ability”. Simplify what it takes for the user to take action – increasing motivation is expensive and time-consuming.




This is the third phase of the Hook Model. You reward the users for taking action by solving their problem or – many times – by simply satisfying the craving for that reward. There are 3 types of variable rewards.

Rewards of the tribe

Social (tribe) rewards are driven by our need for connectedness with other people, making us feel accepted, attractive, important, and included. Tweets, likes, upvotes, re-pins, comments, emails, they all fuel our needs for social validation.

Rewards of the hunt

We used to hunt for food, now we ‘hunt’ for money and information. Working hard for a bonus at work or scrolling through our endless Twitter feed for valuable information are included in this category.

Rewards of the self

The intrinsic rewards of self can make people continue taking action, even on tasks they don’t appear to enjoy. Such rewards address our desire for mastery, competence, and completion.

Infinite Variability

Without infinite variability or novelty in the rewards, however, we tend to lose interest and excitement quickly. Finite variability makes rewards increasingly predictable after use and their appeal is lost over time.

”Businesses nowadays must constantly churn out new content and experiences to cater to their consumers’ insatiable desire for novelty.”

Understand what triggers and motivates the users, and what brings them back, and you’ll get the opportunity to build better habit-forming products.

”Businesses nowadays must constantly churn out new content and experiences to cater to their consumers’ insatiable desire for novelty.”Click To Tweet


This is the fourth and last step in the Hook Model. Before users create habits and automatic behaviours, they must first invest in the product, anticipating longer-term rewards (not immediate gratification).

“Small investments change our perception, turning unfamiliar actions into everyday habits”

This happens because of 3 human tendencies:

  1. The more we invest time & effort into a product, the more we value it,
  2. We seek to be consistent with our past behaviours, and,
  3. We tend to change our preferences to avoid cognitive dissonance.

How can a product keep its users coming back until it becomes a habit? They start by doing small bits of work, like following a user or liking a photo. They gradually move into storing value in the product, such as content (music, photos, posts, etc.), data (about themselves or their behaviours), reputation (followers, upvotes), or skills (investing time to learn the product). Finally, they form the understanding that the service gets better with use.

This makes switching services, difficult, because it means abandoning years of investment and starting over. By loading the next external trigger right after the investment phase, habit-forming technologies get the opportunity to re-engage the user into another cycle of the Hook Model.

“Small investments change our perception, turning unfamiliar actions into everyday habits”Click To Tweet

Consider this…

  • What “bit of work” are your users doing in your product?
  • Brainstorm 3 ways to add small investments into your product to store value as data, content, followers, reputation and skill.
  • How long does it take for a “loaded trigger” to re-engage your users and how can you reduce the delay?



The Hook Model is fundamentally about changing people’s behaviours. However, although creating habits can be a force for good, it can also be addictive and destructive for users.

By answering the two questions “Would I use the product myself?” and “Will the product help users materially improve their lives?” , the makers can assess the morality of a habit-forming product through the Manipulation Matrix.

Facilitators use their own product and believe it can materially improve people’s lives. They facilitate healthy habits and have the highest chance of success because they most closely understand the needs of their users.

Peddlers believe their product can materially improve people’s lives, but do not use it themselves. There’s nothing immoral here, but the odds of designing successful products for a customer they don’t fully understand is low.

Entertainers use their product, but do not believe it can improve people’s lives. Although entertainment does provide joy and connects us with the human condition, building a successful business requires keeping up with the demand for continuous novelty and content.

Dealers neither use the product nor believe it can improve people’s lives. This is the definition of exploitation and they have the lowest chance of finding long-term success.


As the author highlights…

“Running your idea through the four phases of the model will help you discover potential weaknesses in your product’s habit-forming potential.”

Habit Testing helps uncover product devotees, which product elements are habit-forming (if any), and why those aspects of your product change user behaviour. It includes three steps.

  1. Identify

“Who are my product’s habitual users? How often should they use my product?” To find out, use publicly available data from similar products or make realistic and educated assumptions.

  1. Codify

Next, study the steps your habitual users took to understand what hooked them into your product. Look for a “Habit Path” – a series of similar actions shared by your most loyal users.

  1. Modify

Lastly, modify the product to influence more users to follow the same path as your habitual users, and then continue to optimise your processes, content, features, and funnels.


”The first place for the entrepreneur or designer to look for new opportunities is in the mirror.”Click To Tweet

Facilitators start with introspection: instead of asking ‘What problem should I solve?’ , they ask ‘What problem do I wish someone else would solve for me?’ New technology is also a source of opportunities for revolutionary habit-building products:

  • Nascent behaviours – New behaviors that few innovators identify, and yet ultimately fulfill a mainstream need.
  • Enabling technologies – Technologies that suddenly make a behaviour much simpler, faster or more rewarding.
  • New interfaces – Changes in interface suddenly make all sorts of behaviours easier and usage tends to explode.




Key takeaways

  • The Hook Model describes an experience designed to connect the user's problem to a solution frequently enough to form a habit.
  • The 4-step process of the Hook Model is: Trigger, Action, Variable Reward, Investment.
  • Habit-forming products influence the everyday lives and engineer the actions of billions of people.
  • When harnessed correctly, technology can enhance lives through healthful behaviors that improve our relationships, make us smarter, and increase productivity.

Further reading

Sprint by Jake Knapp. A practical guide to answering business questions, Sprint is for anyone with a big opportunity, problem, or idea who needs to get answers today.

The Dip, by Seth Godin, is a quick and easy little ready that teaches you when to quit on ideas, and when to stick with them. If something is worth doing, there will be a dip and you need to learn how to navigate it successfully if you're going to come out the other side.

Guidelines is my eBook that summarises the main lessons from 33 of the best-selling self-help books in one place. It is the ultimate book summary; Available as a 80-page ebook and 115-minute audio book. Guidelines lists 31 rules (or guidelines) that you should follow to improve your productivity, become a better leader, do better in business, improve your health, succeed in life and become a happier person.

Action steps

  1. Go to https://www.nirandfar.com , read the author’s insights on behaviour and business, and subscribe to his weekly newsletter.
  2. Implement the Hook Model on your business and discover how to build positive habit-forming products.
  3. Answer the questions at the end of each chapter.
  4. Download the complete book on Amazon.

This summary is not intended as a replacement for the original book and all quotes are credited to the above mentioned author and publisher.