Book Review: Hooked: How to Build Habit-Forming Products

June 21, 2021

Cover: HookedIn recent years, the perception of UX design has changed dramatically. In the profession’s early days, less mature organizations frequently treated UX professionals as another type of graphic designer, as though UX designers were synonymous with Web designers. But, in today’s leading organizations, UX design is a strategic capability that drives innovation and enhances competitiveness. Similarly, the role of UX professionals has shifted beyond creating functional—if not delightful—user experiences by applying usability, information architecture, and design principles. Now, UX professionals are applying more of their understanding of psychology and human behavior to devising design principles in the service of persuasion.

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Nir Eyal’s book Hooked: How to Build Habit-Forming Products provides an overview of a model for producing habit-forming products. Products that people use habitually occupy a default space in their mind. These products become part of the activities in which people engage when their mind is on autopilot. For those who are familiar with Daniel Kahneman’s Thinking, Fast and Slow, you know that this is the mental state in which we spend most of our waking hours. We don’t actively think about walking, breathing, driving, typing, or other routine activities. When we are on autopilot, we are more susceptible to habit.

Book Specifications

Title: Hooked: How to Build Habit-Forming Products

Author: Nir Eyal, with Ryan Hoover

Formats: Hardcover, Kindle, Audiobook

Publisher: Portfolio

Published: November 4, 2014

Pages: 256

ISBN-10: 0241184835

ISBN-13: 978-0241184837

Benefits of Creating Habit-Forming Products

In his book, Nir Eyal points out that advertising is expensive, and the cost of multichannel ad campaigns is out of reach for all but the largest firms. By utilizing the Hooked model, companies can circumvent the costs of advertising through social sharing, enabling them to spend any advertising budget on the acquisition of new customers at launch, as opposed to reminding users to engage with their product.

Plus, a key metric for most companies is customer lifetime value, which frequent customer interactions and habitual engagement are drivers. However, not every product or service could benefit from the Hooked model. For example, customers rarely engage with their life-insurance provider throughout their relationship with a firm, In contrast, they may use a credit card many times a day. To evaluate a product’s potential for being habit forming, consider two factors: frequency and utility. No matter how much utility a product provides, if customers use it infrequently, using it never becomes a habit. However, even if a product offers only minimal benefits, if customers use it frequently, using it can become a habit.

Of course, every profit-seeking company wants to increase its products’ prices. The Hooked model provides a path forward to increasing prices. Once using a product has become ingrained in the user’s behavior, it becomes easier to increase its price, because the user might perceive shifting to a new product as an arduous task.

It is important to note that Eyal’s Hooked model is about getting people to create a habit relating to a desired activity. While a company could use this superpower, as he describes it, for ill, Eyal promotes the idea that Dark patterns are, essentially, unethical applications of the concepts of the Hooked model.

Concepts of the Hooked Model

Eyal describes the More Is More principle. More frequent usage drives more viral growth. Viral Cycle Time explains the compounding growth of users. More frequent usage and sharing of a product enables the product’s adoption to grow exponentially.

Unfortunately, there is a basic dissonance in the way customers and companies value innovation. Citing John Gorville of Harvard University, Eyal recognizes that many innovations fail because existing users irrationally overvalue the old, while companies irrationally overvalue the new. Because of this phenomenon, products that require behavioral change on the part of users are doomed to fail—unless their perceived benefits are nine times greater than incumbent solutions.

A big reason for users’ resistance to change is that users tend to store value in their tools. Leading companies recognize this. Gmail stores users’ email messages, making it easy for them to access their old email messages. Amazon Prime provides basic video and music libraries. In traditional marketing terms, this increases a customers’ switching costs. It’s the hell people go through when trying to switch from iOS to Android—or when changing their cable-television provider. People could switch, but all of their channels would have different numbers.

Eyal presents an example of the anchoring effect that the Hooked model has on user experiences. Citing a research study that pitted Bing against Google search, researchers found that these search engines anonymized search results were of equal quality. However, because frequent Google users were habituated to the Google user interface, even small differences on Bing led users to perceive it as slower or less effective than Google. This is because understanding the Bing user interface required them exert minimal cognitive effort. Necessitating even the smallest cognitive effort can have a negative effect on the user’s perception of a user experience.

In presenting the Hooked model throughout the book, Eyal provides clear explanations, then offers activities for the reader to perform, helping them to internalize and apply its concepts. Eyal’s Hooked model comprises four parts: Trigger, Action, Variable Reward, and Investment.


Like the bell triggering the salivation of Pavlov’s dog, triggers engage our brains in performing a behavior. Eyal describes two types of triggers: external and internal.

External triggers are easy to identify. They come in the form of text messages, email messages with a call to action, or messages from an app in your smartphone’s notification center. Internal triggers are harder to identify because they reside in the user’s mind. Using internal triggers requires a much deeper understanding of users’ motivations and fears. Strikingly, many internal triggers are associated with negative emotional states such as fear, boredom, envy, and FOMO (Fear of Missing Out).

Eyal recognizes the need to understand users and identifies several UX methods for developing user empathy, including user interviews, empathy maps, and the five-whys method.


According to Eyal’s book, an action is a behavior that a person performs in anticipation of a reward. It is essential that we understand key factors that influence how users perform behaviors, including the ease of performing an action and the psychological satisfaction the user derives from performing that action. As Eyal rightly points out, “Doing must be easier than thinking.”

Eyal draws on B.J. Fogg’s work regarding persuading users to perform a desired behavior, as follows:

  • The user must have motivation (M).
  • The user must have the ability to complete the action (A).
  • A trigger (T) must be present to activate the behavior.

In short, Fogg’s formula is B = MAT.

Eyal applies this formula in his appraisal several technology solutions, including the Log in with Facebook protocol. According to his assessment, a motivation exists: the user wants to log in to a Web site. The ability exists: if the user has a Facebook account. There is a trigger, the application presents the user with a log-in screen. In combination, these factors can lead to a user behavior that enables Web-site owners to essentially outsource their identity and access-management functions, while reducing the friction that users would otherwise experience when logging in to their Web site.

This phenomenon has led to companies’ leveraging users’ Google, Twitter, and LinkedIn accounts in logging into Web sites, easing access for users, while promoting the use of the relevant social-media apps. Of course, this approach requires organizations to trust Facebook to serve as a trustworthy steward of their users’ log-in credentials and user data.

Eyal’s comprehensive chapter on action describes various cognitive heuristics that influence human behaviors, including scarcity, framing, and anchoring biases. The chapter is instructive and advises readers that, when they must choose between cultivating motivation or designing for ability, it is smarter to focus on ability first. Using marketing to incite motivation is expensive and has a limited return on investment (ROI). Plus, users do not usually read instructions. Focusing on motivation would result in the abandonment key performance indicators (KPIs) at work.

Variable Rewards

A variable reward creates a craving through the unpredictability of rewards. For example, Eyal describes a refrigerator’s light coming on. You expect the light to activate when you open its door, so notice only if the light fails to come on. In contrast, if the future is less predictable, your attention is focused, and you anticipate possible outcomes. Dopamine surges when you anticipate a reward. For example, Pinterest meets a need, but showing related content is an unexpected reward. More precisely, the anticipation of a reward entices people more than the actual reward.

People are hardwired to experience delight as a result of variable rewards. As a video-game player anticipates receiving an item in a supply drop in Fortnite or a prehistoric hunter risks his life to hunt larger prey, human beings embrace the potential for prizes.

Some have hypothesized that our embrace of uncertainty is part of what makes humor. If I asked you, “Why do we tell actors to break a leg?” you could respond with the actual answer: “Superstition, because wishing someone good luck might attract the attention of evil spirits.” Or you could respond, “Because every play has a cast.” One reply is rational and follows a logical course, while the other takes an unexpected turn, so is more delightful. It also shows how explaining a joke ruins it.


Investment, the final step in the Hooked model, consummates the user’s relationship with the user experience. During this phase of an interaction, the user puts something into it: time, personal information, reputation, or, in some cases, money. The promise of their investment is that it would improve subsequent interactions, so it primes them for their next activity.

You can easily find examples of investment—for example, in the onboarding processes for Pinterest, Facebook, and LinkedIn. In the case of LinkedIn, the application presents users with a graph that illustrates the strength of their profile, encouraging them to divulge more information about themselves. The demand for investment is even more egregious in video games, in which the user can pay for credits that give them a virtual benefit such as weapons, superpowers, or farm equipment. In my mind, this is an extension of the sunk-cost fallacy: people continue to expend their resources even after previously wasting resources to avoid the cognitive dissonance of realizing their earlier poor decisions.

Investment can go even further in cases where users share their behaviors, inviting their friends to participate in their experience and fulfilling the More Is More principle the book articulated early on.


Hooked is an engaging read. Eyal does a good job of describing and encapsulating the principles that the book describes and advising readers on how to apply them to the design of habit-forming products. When I originally encountered this book, I was concerned that it might be full of dark patterns, but it was not. Nevertheless, I appreciated that Eyal acknowledges the potential for its principles’ misuse. However, as with Nudge, I especially value the book’s optimism. We can build habit-forming products that help people.

We don’t need to trick people into giving us their personal information so we can spam their contacts. We don’t need to make it hard to cancel subscriptions to our products. We don’t need to encourage endless scrolling with algorithms that produce negative feedback loops and sometimes deprive users of sleep.

Instead, we can apply the same principles to create habit-forming products that encourage people to exercise, eat healthy foods, attend to their financial wellness, and generally encourage more satisfying outcomes for people. We can help people to live better lives. 

Owner and Principal Consultant at Covalent Studio LLC

Akron, Ohio, USA

D. Ben WoodsBen’s global design and technology firm specializes in software design and development for the Web, mobile, and ecommerce. The company serves clients ranging from small startups to some of the largest companies in the world, including General Electric, Rio Tinto, and Fidelity. His career in User Experience began in the late 1990s. Ben has held diverse roles, including UX management at a global B2B firm, full-time and part-time academia, and executive roles. He enjoys solving complex business problems and coaching talent to be competitive UX design professionals. Ben earned his MS in Information Architecture and Knowledge Management at Kent State University and is a graduate of the Executive MBA program at Case Western Reserve University’s Weatherhead School of Management. He has presented long-format talks, speed presentations, and posters at many conferences and events and has conducted training and workshops for organizations throughout the United States, Europe, and Asia.  Read More

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