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Hooked - Book summary

Why are certain products or services so addictive while others fail? In this book, Nir Eyal explains the role of habits in successful products/services, and how you can use the 4-step Hook Model to shape customer behaviors and habits. In this free version of the Hooked summary, we’ll give an overview of the benefits of building habit-forming technologies, and how you can get customers hooked with a 4-part strategy.

Hooked: Creating Habit-Forming Products

To have a massively successful business like Google or Facebook, it’s not enough to have the marketing muscle to reach lots of people. You must learn to leverage human habits and emotions and get people to use your product so regularly that it becomes a habit.

Habit-forming companies offer first-to-mind solutions, i.e. they become so strongly associated with a problem/need that people automatically reach for these solutions when the triggers appear. For example, you’ll automatically think of Google when you need to search for information, or start scrolling through your Facebook or Instagram feeds when you’re bored or lonely.

The question is, how do you develop such an association and get people hooked? The key is to create a series of hooks and experiences that lock people into using your products habitually.

In our complete Hooked summary, we’ll elaborate on:

  • How you can use user habits to lock in several benefits including: higher customer lifetime value, greater price flexibility, accelerated growth and competitive advantages;
  • The difference between offering a solution that’s a painkiller vs a vitamin; and
  • The 2 factors that affect whether your product will fall into the “Habit Zone” and get users hooked.

Now, we’ll take take a quick look at how you can use Nir Eyal’s 4-part Hook Model to embed habit-forming cycles into a product/service.

The 4 Steps of the Hook Model

The Hook Model involves 4 steps that run in a loop or cycle: Trigger => Action => Variable reward => Investment.
Hooked summary_4-step Hook Model


Habits happen when a trigger automatically brings about a behavior. Such habits are formed in layers over time; they aren’t developed overnight.

2 Types of Triggers

  • External triggers provide an obvious call-to-action, i.e. they tell people what to do. These can come in the form of pictures, text, and/or explicit instructions e.g. “Click here” or “Call this number”. A well-designed trigger has so much information embedded that it doesn’t require long instructions on what to do. There’re 4 key types of external triggers: paid, earned, relationship and owned triggers (more details in our full Hooked summary).
  • Internal triggers. An internal trigger is formed when a product becomes tied with a thought, routine, or emotion. When a product relieves a pain-point, you associate certain feelings with it. As the experience is repeated, the association is strengthened, until you automatically reach for those products for quick relief whenever you experience the internal triggers. That’s why smokers feel the urge for a cigarette when they’re stressed. People turn to Google when they want certainty (to find/verify certain information).
  • External => Internal triggers. Habit-forming technologies start with external triggers to prompt repeated actions, until these become closely linked to internal triggers. Imagine you’re new to Instagram. You receive an external trigger (a friend’s recommendation), which prompts you to create an account. This is followed by a series of external triggers (e.g. push notifications, friends’ pictures, comments and “likes” in response to your posts), all of which prompt you to keep using Instagram. After a while, you’re so used to snapping photos on Instagram that you’re afraid to miss a special moment if you don’t snap it.

Do get our full book summary for more tips and action steps on how to develop the right triggers.


A trigger is useless unless it creates real action. And, people will only take action if the desire outweighs the effort (mental/physical).

According to Dr. BJ Fogg, Behavior = Motivation + Ability + Trigger (B = MAT). To successfully trigger action, you must make it easy to perform the action, increase the motivation to do it, and have an effective trigger.

Earlier, we’ve already touched on Triggers. In our complete 16-page summary, we elaborate further on:

  • The 3 key sets of motivators + 6 elements that affect our ability to complete the desired action; and
  • 4 mental biases or heuristics that influence our decisions.
  • Tips for implementing this step.


Dopamine is a pleasure-inducing chemical that’s released when we experience or expect a reward. Once we learn that something predictably delivers a reward, the anticipation of the reward is already enough to activate dopamine release.

To form habits, your product must solve a real problem consistently and reliably. Yet, if something becomes so predictable that we know exactly what will happen, we lose attention. Variable rewards increase the likelihood that we’ll keep doing something because we’re anticipating a reward and curious to see what variation we’ll get. This increases the effects of dopamine.

Do check out our complete Hooked summary for more details on:

  • The 3 key types of variable rewards you can use; and
  • Specific tips and action steps to implement your variable rewards.


In order for a behavior to become automatic, users must complete this final step—they must invest in the product by putting in their time, effort, money, social capital etc. The more users invest in your product, the more they’ll return to use it because of how we rationalize our behaviors.

Do get our full book summary for (i) the human psychology behind this step and (ii) specific tips for implementation.

Applying the Hook Model

In the book, Nir Eyal, also presents several frameworks and tips to help us implement the Hook Model responsibly, ethically and effectively. Do get a detailed overview from our full Hooked summary bundle.

Hooked summary_implementing the hook model

This includes:

  • The Manipulation Matrix: to help us consider the implications of your innovation, including if you can and should hook your users.
  • A Habit Testing process to figure out which of your ideas actually work; and
  • Tips for uncovering new habit-forming opportunities.

Getting the Most from Hooked

In this article, we’ve briefly outlined some of the key insights and strategies you can use to achieve desired change. For more examples, details, and actionable tips to apply these strategies, do get our complete book summary bundle which includes an infographic, 16-page text summary, and a 27-minute audio summary.Hooked summary - book summary bundle

This is an easy-to-read book that includes many real-life examples, case studies and useful empirical research/background. Each chapter comes with a brief summary and recommended questions/exercises to help you get started. You can purchase the book here for the full details, or check out more resources/details at

You can also learn more about the science of habits formation in The Power of Habit summary or learn how to apply it to change any aspect of your life with Atomic Habits summary.

About the Author of Hooked

Hooked: How to Build Habit-Forming Products is written by Nir Eyal–an Israeli-born American author, lecturer and investor. He earned a B.A. at Emory University, worked for Boston Consulting Group and a solar panel installation firm before graduating with a Master of Business Administration from Stanford. He then founded a digital marketing company with his friends before becoming a consultant in product design. Eyal also teaches university courses and gives speeches about how psychology intersects with technology and business.

Hooked Quotes

“Careful introspection can uncover opportunities for building habit-forming products.”

“Instead of asking ‘what problem should I solve?’ ask ‘what problem do I wish someone else would solve for me?’”

“Wherever new technologies suddenly make a behavior easier, new possibilities are born.”

“Hooks connect the user’s problem with a company’s solution frequently enough to form a habit.”

“Once we come to depend on a tool, nothing else will do.”

“To initiate action, doing must be easier than thinking.”

Click here to download the Hooked summary & infographic

One Comment

  • kmohror says:

    ReadinGraphics is a compelling curation service that delivers practical, immediately actionable knowledge. Every Wednesday on LinkedIn I will share and / or send RiG posts to groups I am in and to my network. I focus on enabling better selfcare by people with an emphasis on preventing heart disease.


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