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Hooked by Nir Eyal

I read Hooked: How to Build Habit-Forming Products by Nir Eyal at Barnes & Noble. It’s a 1 cup of coffee read.

I LOVED this book. I’ll start by saying that. And if you’re an online product or service creator, you will love this book too.

I read a LOT of books. And I get value from most of the books I read. However, not all of them keep me on the edge my seat like Hooked did. I was literally hooked as soon as I started reading this book.

It was his pragmatic use of studies mixed with definitions and explanations that resonated with me. And the book was a surprisingly quick read given the amount of information I extracted from it.

Here’s a summary of what I learned.

The Hook Model

Eyal defines the hook model as:

Trigger –> Action –> Variable Reward –> Investment

A trigger is the actuator of behavior–the spark plug in the engine.

The action is the simplest behavior in anticipation of reward.

In the variable reward phase, you reward your users by solving a problem, reinforcing their motivation for the action taken in the previous phase.

The investment occurs when the user puts something into the product or service such as time, data, effort, social capital, or money.

These experiences, or hooks as the author calls them, alter our every day behavior, to eventually, and potentially, form habits.

Why are forming habits good for business?

Eyal says, “Habit-forming products change user behavior and create unprompted user engagement.” He goes onto say that, “Fostering consumer habits is an effective way to increase the value of a company by driving higher customer lifetime value (CLTV): the amount of money made from a customer before that person switches to a competitor, stops using the product, or dies.”

Habits are tough to break, which makes switching to a competing product or service difficult. “The enemy of forming new habits is past behaviors,” Eyal writes.

He gives the example of Google vs Bing, which at this point, offer almost identical search services. Why then, are Google users so reluctant to switch?

Eyal writes, “Although many aspects of Bing are similar to Google, even a slight change in pixel placement forces the would-be user to leave a new way of interacting with the site. Adapting to the differences in the Bing interface is what actually slows down regular Google users and makes Bing feel inferior, not the technology itself.”

So in other words, in order for a user to switch to a competing product, it can’t just be a little better, it has to be A LOT better. The reason why many new products or services don’t make it is because the difference isn’t great enough between how much better the new product is versus how much users love their existing product.

Eyal writes, “A classic paper by John Gourville, a professor of marketing at Harvard Business School, stipulates that ‘many innovations fail because consumers irrationally overvalue the old while companies irrationally overvalue the new.'”

This is why understanding how the Hook Model works is crucial for new product survival. Eyal walks us in detail through the Hook Model, section by section in the book. I’ll provide a basic summary of each section.

The Trigger

As we learned, the trigger is what starts the process. Eyal explains that there are three core motivators that drive human behavior, “seeking pleasure and avoiding pain, seeking hope and avoiding fear, seeking social acceptance while avoiding social rejection.”

He uses the example of Instagram to explain how strong associations with internal triggers can become a routine.

With Instagram, Eyal writes, “It is the fear of losing a special moment that instigates a pang of stress. This negative emotion is the internal trigger that brings Instagram users back to the app to alleviate this pain by capturing a photo. As users continue to use the service, new internal triggers form.”

When Eyal refers to pain, it’s not as painful as it may sound. Not every pain we experience is excruciating.

Eyal writes, “It is important to clarify that the term pain, as it is frequently used in business school and marketing books, is somewhat hyperbolic. In reality, the experience we are talking about is more similar to an itch, a feeling that manifests within the mind and causes discomfort until it is satisfied.”

How do we discover the pain?

If the pain ultimately helps us discover the trigger, how can we as product creators find the pain?

One method of discovering the pain Eyal discusses is asking why as many times as it takes to get to an emotion. This technique is described by Taiichi Ohno, considered the father of the Toyota Production System, as the “5 Whys Method”, which Ohno described as the basis of Toyota’s scientific approach.

Eyal gives an example of this method in a fictitious scenario where we hypothetically develop the technology called “e-mail”.

…let’s say we’re building a fancy new technology called e-mail for the first time. The target user is a busy middle manager named Julie. We’ve built a detailed narrative of our user, Julie, that helps us answer the following series of whys:

Why #1: Why would Julie want to use e-mail?
Answer: So she can send and receive messages.

Why #2: Why would she want to do that?
Answer: Because she wants to share and receive information quickly.

Why #3: Why does she want to do that?
Answer: To know what’s going on in the lives of her coworkers, friends, and family.

Why #4: Why does she need to know that?
Answer: To know if someone needs her.

Why #5: Why would she care about that?
Answer: She fears being out of the loop.

Now we’ve got something! Fear is a powerful internal trigger and we can design our solution to help calm Julie’s fear.

External vs Internal Triggers

There are two types of triggers, external and internal, which work in conjunction with one another to drive users to take action.

“The ultimate goal of all external triggers is to propel users into and through the Hook Model so that, after successive cycles, they do not need further prompting from external triggers,” Eyal writes. “When users form habits, they are cued by a different kind of trigger: internal ones.”

Eyal discusses four types of external triggers:

  1. Paid Triggers such as advertising or search engine marketing.
  2. Earned Triggers like public and media relations, press mentions, featured placements.
  3. Relationship Triggers like word of mouth of social sharing.
  4. Owned Triggers such as app notifications, e-mail newsletters, and product notifications.

Eyal describes the relationship between the four types of external triggers. “While paid, earned, and relationship triggers drive new user acquisition, owned triggers prompt repeat engagement until a habit is formed. Without owned triggers and users’ tacic permission to enter their attentional space, it is difficult to cue users frequently enough to change their behavior.”

For example, a relationship trigger such as your friend using the service, is what may have gotten you onto Facebook in the first place. But once you’re an active member, and you install the app on your phone, the owned triggers, aka: Facebook notifications, are what keep you reengaged and coming back. Once you reach that point, the notifications bring you back more than the initial external trigger of your friend being on Facebook and encouraging you to join.

The other goal of external triggers, aside from triggering the user to take action, is to transition the user towards internal triggers. Eyal writes, “Once we’re hooked, using these products does not always require an explicit call to action. Instead, they rely upon our automatic responses to feelings that precipitate the desired behavior.”

In the example earlier with Instagram, the internal trigger is the fear of losing a special moment. This fear prompts the user to pull out their phone, capture a photo, and share it on Instagram with their network. This is the action.

In the other example of Facebook, the need for social acceptance, or the fear of being lonely, acts as the internal trigger that gets us to pull out our phones and scroll through the News Feed.


The second phase of the Hook Model is the action.

If the user doesn’t take action, the trigger is useless. So in order to maximize the number of users to take action, the action has to be easy.

Eyal writes, “Remember, a habit is a behavior done with little or no conscious thought. The more effort–either physical or mental–required to perform the desired action, the less likely it is to occur.”

Eyal discusses the Fogg Behavior Model, “which represents that a given behavior will occur when motivation, ability, and a trigger are present at the same time and in sufficient degrees.” This model was developed by Dr. B.J. Fogg, Director of the Persuasive Technology Lab at Stanford University, as a way to understand what drives our actions.

What is motivation?

Eyal writes that “Dr. Edward Deci, Professor of Psychology at the University of Rochester and a leading researcher on the self-determination theory, defines motivation as ‘the energy for action.'”

When the energy for action is met with the ability to take action, then the action can occur, if triggered.

What is ability?

Ability, according to Fogg, is influenced by six factors which are time, money, physical effort, brain cycles, social deviance, and non-routine.

Eyal writes, “To increase the likelihood that a behavior will occur, Fogg instructs designers to focus on simplicity as a function of the user’s scarcest resource at that moment.”

There are other factors which lead to action or inaction, such as perception, framing, and progress, which Eyal goes into detail about in this section.

Eyal writes that, “People often anchor to one piece of information when making a decision.”

The key for product creators when triggering action is focusing on the right piece of information, that is inline with their audience’s pain and/or goals. If the product creator is successful at creating user action, the next step in the Hook Model is the reward.

Viable Reward

In the viable reward stage of the Hook Model, Eyal writes, “you reward your users by solving a problem, reinforcing their motivation for the action taken in the previous phase.”

Eyal says that our brains are wired to seek rewards that make us feel accepted, attractive, important, and included.

Eyal explains viable rewards in terms of something we’re all familiar with, social media:

It is no surprise that social media has exploded in popularity. Facebook, Twitter, Pinterest, and several other sites collectively provide over a billion people with powerful social rewards on a variable schedule. With every post tweet, or pin, users anticipate social validation. Rewards of the tribe keep users coming back, wanting more.

Sites that leverage tribal rewards benefit from what psychologist Albert Bandura called “social learning theory.” Bandura studied the power of modeling and ascribed special powers to our ability to learn from others. In particular Bandura determined that people who observe someone being rewarded for a particular behavior are more likely to alter their own beliefs and subsequent actions. Notably, Bandura also demonstrated that this technique works particularly well when people observe the behavior of people most like themselves or who are slightly more experienced (and therefor, role models). This is exactly the kind of targeted demographic and interest-level segmentation that social media companies such as Facebook and industry-specific sites such as Stack Overflow selectively apply.

The reward can come in many forms though, not just social validation. You see many businesses and websites attempt to “gamify” their products and services with varying success.

FourSquare, for example, gives users badges the more they Check In to business locations. helps users track their financial goals with a variety of goal tracking tools, charts, and graphs. users earn reputation points by convincing their peers that they know what they’re talking about. Reddit has Karma Points. Quora gives user credits for adding content. Khan Academy gives users badges for completing courses.

The examples of gamification are endless, and you are probably able to think of a few examples of products and services you use that attempt to gamify your experience (whether successfully or unsuccessfully).

Eyal writes, “Points, badges, and leaderboards can prove effective, but only if they scratch the user’s itch. When there is a mismatch between the customer’s problem and the company’s assumed solution, no amount of gamification will help spur engagement.”

“But You Are Free”

The most fascinating study I read about in Hooked was a French study where researchers discovered a technique to influence how much money people gave a total stranger in various circumstances. In the study, a stranger increased the amount of people who gave him bus fare by inserting just a few specially encoded words at the end of his request. The special phrase proved to be effective in other areas too such as increasing donations to charity and increasing participation in voluntary surveys.

Do you know what the phrase was? The person added to the end of their proposition, “But you are free to accept or refuse.”

Why does this simple phrase increase user action (ie: donations)?

Eyal writes, “The researchers believe the phrase: ‘But you are free’ disarms our instinctive rejection of being told what to do.” And we all hate being told what to do! (Or is that just me?)

He continues, “If you have ever grumbled at your mother when she tells you to put on a coat or felt your blood pressure rise when your boss micromanages you, you have experienced what psychologists term reactance, the hair-trigger response to threats to your autonomy.”


The fourth stage of the Hook Model is investment, which Eyal writes, “occurs when the user puts something into the product or service such as time, data, effort, social capital, or money.”

He explains that “investments” aren’t always just monetary, but rather things users do to improve their experience with the product or service.

For example, Eyal writes that “inviting friends, stating preferences, building virtual assets, and learning to use new features are all investments users make to improve their experience. These commitments can be leveraged to make the trigger more engaging, the action easier, and the reward more exciting with every pass through the Hook cycle.”

Why do these small investments increase our loyalty and engagement in a product?

Eyal explains the psychological phenomenon known as the escalation of commitment. He writes, “The more users invest time and effort into a product or service, the more they value it.”

Eyal gives a perfect example of this with the furniture retailer IKEA:

IKEA, the world’s largest furniture retailer, sells affordable, ready-to-assemble household furnishings. The Swedish company’s key innovation is its packaging process, which allows the company to decrease labor costs, increase distribution efficiency, and better utilize the real estate in its stores.

Unlike its competitors who sell preassembled merchandise, IKEA puts its customers to work. It turns out there’s a hidden benefit to making users invest physical effort in assembling the product–by asking customers to assemble their own furniture, Ariely believes they adopt an irrational love of the furniture they build, just like the test subjects did in the origami experiments. Businesses that leverage user effort confer higher value to their products simply because their users have put work into them. The users have invested in the products through their labor.

Our investments increase the value we get from products and services, because we are often more likely to be consistent with our own past behaviors.

Eyal writes, “We change our preferences to avoid cognitive dissonance.” defines cognitive dissonance as “a situation involving conflicting attitudes, beliefs or behaviors. This produces a feeling of discomfort leading to an alteration in one of the attitudes, beliefs or behaviors to reduce the discomfort and restore balance etc.”

A classic example of cognitive dissonance is most people’s reaction to alcohol the first time we try it.

Eyal explains, “Our innate reaction to these acquired tastes is to reject them, yet we learn to like them through repeated exposure. We see others enjoying them, try a little more, and over time condition ourselves. To avoid the cognitive dissonance of not liking something that others seem to take so much pleasure in, we slowly change our perception of the thing we once did not enjoy.”

Once we reach the point where we change our attitudes and beliefs to adapt to our preferences, we begin to rationalize our actions.

Eyal writes, “Rationalization helps us give reasons for our behaviors, even when those reasons might have been designed by others.”

When a product creator can successfully take a user through the Hook Model, the user begins to form habits, and the cycle starts over again. “Habit-forming technologies leverage the user’s past behavior to initiate an external trigger in the future,” Eyal explains.

Good or Evil?

Eyal ends the book discussing the responsibility product makers have when creating user habits. The ability to create habits could be used for positive or negative change.

At one point, a reader of Eyal’s blog wrote him an e-mail that said, “If it can’t be used for evil, it’s not a superpower.”

Eyal agrees. He writes, “Creating habits can be a force of good, but it can also be used for nefarious purposes.”

Manipulation often has a negative connotation. Even the word “manipulation” has an evil feel to it. But Eyal gives examples of when manipulation can be used for changing behavior for the better. He gives the example of Weight Watchers, “one of the most successful mass-manipulation products in history… Weight Watchers customers’ decisions are programmed by the designer of the system, yet few question the morality of the business.”

Ultimately the responsibility of using this knowledge of the Hook Model falls into the hands of the product creators. “When harnessed correctly,” Eyal writes, “technology can enhance lives through healthful behaviors that improve our relationships, make us smarter, and increase productivity.”

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