Synopsis – Hooked: How to Build Habit Forming Products


Cognitive psychologists define habits as, “automatic behaviors triggered by situational cues:” things we do with little or no conscious thought. Therefore, the products and services we habitually use alter our everyday behavior, engineering our actions. Written by Nir Eyal, this book primarily discusses the Hook Model: a four-phase process that companies use to form habits. Through consecutive Hook cycles, successful products reach their ultimate goal of unprompted user engagement, bringing users back repeatedly without depending on costly advertising or aggressive messaging. Many social media sites, for example, have achieved this as users unconsciously scroll through their feeds to kill time while waiting in lines.


The convergence of access, data, and speed is making the world a more habit-forming place. Therefore, companies are increasingly finding that their economic value is a function of the strength of the habits they create. This habit formation can lead to increased customer lifetime value, pricing flexibility (customers become less price sensitive when they have formed a habit using a product), supercharged growth (the viral cycle time is accelerated when users continuously find value in a product and invite their friends), and competitive advantage. Eyal provides a unique example for habit formed competitive advantage, noting how the QWERTY keyboard is inferior to existing alternatives in many ways. It was first developed in the 1870s for the now-ancient typewriter, yet is limited in comparison to the Dvorak Simplified Keyboard which places vowels in the center row and increases typing speed and accuracy. However, the QWERTY keyboard survives due to the high costs of changing user behavior. To pull a term form accounting, human behaviors are LIFO, “last in, first out.” Essentially, recently acquired habits are also the ones most likely to go soonest, therefore people rarely change their habits for long unless the behaviors occur with high frequency, i.e. flossing or Googling.

Eyal succinctly ties these initial ideas together with an interesting proposition for entrepreneurs: Are you building a vitamin or a painkiller? Painkillers have quantifiable markets and clear purposes, while vitamins appeal to a user’s emotional rather than functional needs. In the end, he concludes that habit forming technologies possess a bit of both purposes. At first they seem to be nice-to have vitamins, but once the habit is established, they provide an ongoing pain remedy for the habitual itch.


To move beyond the habit-forming zone, Eyal then analyzes the four phases of the Hook model: trigger, action, variable reward, and investment.

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A trigger is the actuator of behavior – the spark plug in the engine. Eyal likens this phase to a pearl, in which the arrival of a tiny irritant triggers the oyster’s system to begin blanketing the invader with layers of shimmery coating, eventually accumulating to a pearl.  Similarly, new habits need foundations and triggers are the basis for sustained changes in behavior. In the beginning, external triggers are used to acquire users. This occurs through paid triggers, earned triggers (like PayPal, once someone sends you money it creates a large incentive or open an account), relationship triggers (creating engaged users that expand the network), and owned triggers (recognizing app icons, push notificiations).

Consequently, these external factors couple products with thoughts and emotions that create internal triggers. These internal triggers are vastly instigated by emotions, with negative emotions being the most powerful because they propel actions that quell the negative sensations, i.e. FOMO is currently a large action driver. Once a product has created an association in a user’s mind that it provides a solution, users return on their own without external prompts. This learned association becomes encoded in the user’s memory, which is the ultimate goal. Because these internal triggers are intangible, Eyal also highlights the 5 Why’s Method. This method involves asking the question “why” as many times as it takes to stir an emotion, which drills right to the core of why people use habit forming products.


Eyal uses the Fogg Behavior Model to breakdown behavior initiators. This model is represented by B=MAT, in which a given behavior will occur when motivation, ability, and a trigger are all present at the same time. The three core motivators are to seek pleasure and avoid pain, seek hope and avoid fear, and seek social acceptance and avoid rejection. Ability is influenced by elements of simplicity, including time, money, physical effort, brain cycles, social deviance, and non-rountineness. He cites the streamlined and simple Google homepage to show that reducing the effort required to perform an action is more effective than increasing desire to do it.

Eyal also explores the influence of heuristics in action-taking. Heuristics are the mental shortcuts used to make decisions and form opinions. The scarcity heuristic can decrease perceived product value if it starts off as scarce and later becomes abundant. The framing heuristic can alter pleasure levels based on situational context. In contrast, endowed progress effect increases motivation if people believe they are nearing a goal. This could be done by giving out a car wash punch card with 2 out of 10 holes already punched, which compels customers to complete the last 8 holes on the card. These slight cognitive biases influence our decisions multiple timers per day and can help producers achieve desired user action.


We are driven to act to alleviate a craving for a reward. This craving, however, can be perpetuated by a degree of novelty which maintains user attention. This variability spikes chemical levels in our brain, thus driving a continual search for rewards. Variable rewards come in three types.

  • Rewards of the tribe are social and driven by our connectedness with others. We seek social validation in our posts to feel accepted, attractive, and included. This pulls from Bandura’s social learning theory in which we alter our own beliefs based on observations of others. Thus, it is no surprise that social media use has exploded in popularity.
  • Rewards of the hunt fulfill the need to acquire resources and information. While we once hunted for food, Eyal ties in more modern examples. When users scroll to the bottom of a Pinterst page, some images are cut-off. While barely visible, users continue scrolling to relieve their curiosity which leads to the endless hunt. Gambling is another example, with slot machines that reward money in random intervals and people become addicted to the pursuit of a jackpot.
  • Rewards of the self lead to personal gratification through the completion of tasks and the conquering of obstacles. We have intrinsic motivation to gain a sense of competency, thus many are compelled to master video-games or even mindlessly clear their email inboxes.

It is also noted that companies must match the right variable reward to their intended behaviors and they must maintain a sense of user autonomy in the process.

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Before users create the mental associations that activate their automatic behaviors, they must first invest in the product. Three tendencies influence future actions and anticipated rewards: (1) the more time and effort put into something, the more likely we are to value it, (2) we likely to be consistent with our past behaviors, (3) we change our preferences to avoid cognitive dissonance. Typically, the investment is asked for after the user has already received a reward. The model is then perpetuated as the user experience enhances each time through the cycle with the accrual of content, data, followers, reputation, or skill.


When harnessed correctly, technology can enhance lives through behaviors that improve our relationships, make us smarter, and increase productivity. But is this subliminal habit formation moral?  Eyal concludes with an analysis of user manipulation (based on if products can materially improve user’s lives). He also provides a case study on the success of the Bible App, which places more interesting content up-front and separates verses into smaller sections.


Overall, this book was clearly written and well organized. I would recommend it to any aspiring startup founder, product designer, marketer, or simply anyone who is curious about why they mindlessly click on the Instagram app when waiting in line or riding an elevator. It provides a framework that is applicable to the technology we use daily and a deep understanding of how products influence human behvaior.

I personally enjoyed the abundance of relevant examples throughout the book and the end of chapter summaries to reinforce key points. Furthermore, Eyal makes it extremely easy for entrepreneurs to apply these ideas by adding a “Do This Now” section at the end of each chapter to really analyze aspects of their product ideas. The book description accurately states that Eyal wrote the book he wished had been available to him as a startup founder – not abstract theory, but a how to guide for building better products.

However, I also would warn that it can be redundant at times and likely could be stated more succinctly. Though Eyal spent a paragraph addressing the importance of developing user habits and not addictions, some may argue that this book highlights ways to develop user habits far beyond just a “nudge” and monetize on the quirks of human behavior. Overall, though, it provides valuable insight on how to maintain customer engagement in a very competitive modern market.

4 thoughts on “Synopsis – Hooked: How to Build Habit Forming Products

  1. Hi Abby! It is definitely interesting in reading this summary to identify how I, myself, have been subject to these habit forming practices as a consumer. Also fascinating–and not at all surprising– how much a typical consumer is affected by social influence (like what their friends are doing) and how companies are identifying ways to take advantage of that. Sounds like an interesting book!


  2. Nice summary. This book is one of the few on the list that I haven’t read, but I’ve heard interesting things about it. Its definitely on my list of ones to get to, and I suspect that these themes will actually come up during our first class discussion next week.


  3. This was a very informative summary for me because I had no idea that there was such a systematic approach behind making these habit-forming products. I think it is fascinating that technology companies have been able to create a product that is just as natural as eating, breathing, or sleeping. When I am confused about something, I turn to Google without even thinking about it. If I am bored, then my hands pull out my iPhone and go on Instagram, but the conscious thought, “I am bored. Let’s go on Instagram,” never crosses my mind. These companies have been able to associate their products with complex human emotions (Instagram and boredom) and I think that is just incredible.


  4. I love the psychology of this! It’s almost creepy that scientists have managed to tap into the cognitive ways to form habits. You explained these concepts really well in your summary, and based on the anecdotes you mentioned, I could see how the book’s anecdotes would be fascinating (like the punch cards!) It’s interesting that this book was written as a guide to entrepreneurs…I usually would expect psychological books like this to be more theory-based than practice-based.


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