Hooked: How to Build Habit-Forming Products - by Nir Eyal


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This another great book with lots of actionable information. Whether you're building digital or physical products, you won't be disappointed.

Recommendation: 5/5

My Highlights

Cognitive psychologists define habits as “automatic behaviors triggered by situational cues”: things we do with little or not conscious thought.

First To Mind Wins

Companies that form strong user habits enjoy several benefits to their bottom line. These companies attach their product to internal triggers. As a result, users show up without any external prompting.

...habit-forming companies link their services to the user’s daily routines and emotions.

How do products create habits? The answer: They manufacture them.

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.

The Hook Model

  • Trigger
  • Action
  • Variable Reward
  • Investment

1. Trigger:

A trigger is the actuator of behavior... Triggers come in two types: external and internal. Habit-forming products start by alerting users with external triggers like an e-mail, a Web site link, or the app icon a phone.

When users start to automatically cue their next behavior, the new habit becomes part of their everyday routine.

2. Routine:

Following the trigger comes the action: the behavior done in anticipation of a reward.

Companies leverage two basic pulleys of human behavior to increase the likelihood of an action occurring: the ease of performing an action and the psychological motivation to do it.

3. Variable Reward:

What distinguished the Hook Model from a plain vanilla feedback loop is the Hook’s ability to create a craving. Feedback loops are all around us, but predictable ones don’t create desire.

Variable rewards are one of the most powerful tools companies implement to hook users...

Research shows that level of the neurotransmitter dopamine surge when the brain is expecting a reward. Introducing variability multiplies the effect, creating a focused state, which suppresses the areas of the brain associated with judgement and reason while activating the parts associated with wanting and desire.

4. Investment:

The last phase of the Hook Model is where the user does a bit of work. The investment phase increase the odds that the user will make another pass through the Hook cycle in the future. The investment occurs when the user puts something into the product of service such as time, data, effort, social capital, or money.

...the investment implies an action that improves the service for the next go-around. Inviting friends, stating preferences, building virtual assets, and learning to use new feature 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.

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

  • Habits are defined as “behaviors” done with little or no conscious thought.”
  • The convergence of access, data, and speed is making the world a more habit-forming place.
  • Businesses that create customer habits gain a significant competitive advantage.
  • The Hook Model describes an experiences designed to connect the user’s problem to a solution frequently enough to form a habit.
  • The Hook Model has four phases: trigger, action, variable reward, and investment.

Habits are one of the ways the brain learns complex behaviors. Neuroscientists believe habits give us the ability to focus our attention on other things by storing automatic responses in the basal ganglia, an area of the brain associated with involuntary actions.

Habits form when the brain takes a shortcut and stops actively deliberating over what to do next. The brain quickly learns to codify behaviors that provide a solution to whatever situation it encounters.

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. User habits increase how long and how frequently customers us a product, resulting in higher CLTV.

...as customers form routines around a product, they come to depend upon it and become less sensitive to price.

...habits give companies greater flexibility to increase prices.

...in the free-to-play vide game business, it is standard practice for game developers to delay asking users to pay money until they have played consistently and habitually. Once the compulsion to play is in place and the desire to progress in the game increase, converting user into paying customers is much easier. The real money lies in selling virtual items, extra lives, and special powers.

Users who continuously find value in a product are more likely to tell their friends about it. Frequent usage creates more opportunities to encourage people to invite their friends, broadcast content, and share through word of mouth. Hooked users become brand evangelists—megaphones for your company, bringing in new users at little or no cost.

Products with higher user engagement also have the potential to grow faster than their rivals.

...more frequent usage drive more viral growth.

Having a greater proportion of users daily returning to a service dramatically decreases Viral Cycle Time for two reasons: First, daily user initiate loops more often...second, more daily active user means more people to respond and react to each invitation. The cycle not only perpetuates the process—with higher and higher user engagement, it accelerates it.

Products that change customer routines are less susceptible to attacks from other companies.

...”many innovations fail because consumers irrationally overvalue the old while companies irrationally overvalue the new.”

...users also increase their dependency on habit-forming products by storing value in them—further reducing the likelihood of switching to an alternative.

...user habits increase a business’s return on investment. Higher customer lifetime value, greater pricing flexibility, supercharged growth, and a sharpened competitive edge together equal a more powerful bang for the company’s buck.

For new behaviors to really take hold, they must occur often.

...frequent engagement with a product—especially over a short period of time—increases the likelihood of forming new routines.

...a behavior that occurs with enough frequency and perceived utility enters the Habit Zone, helping to make it a default behavior. IF either of these factors falls short and the behavior lies below the threshold, it is less likely that the desired behavior will become a habit.

Some behaviors never become habits because they do not occur frequently enough. No matter how much utility is involved, infrequent behaviors remind conscious actions and never create the automatic response that is characteristic of habits. On the other axis, however, even a behavior that provides minimal perceive benefit can become a habit simply because it occurs frequently.

...some habits can be formed in a matter of weeks while other can take more than five months.

...the complexity of the behavior and how important the habit was to the person greatly affected how quickly the routine was formed.

...higher frequency is better.

...one aspect is common to all successful innovations—they solve problems.

Painkillers solve an obvious need, relieving a specific pain, and often have quantifiable markets.

Vitamins, by contrast, do not necessarily solve an obvious pain point. Instead they appeal to users’ emotional rather than functional needs

A habit is when not doing an action causes a bit of pain.

The habit-forming products we use are simply there to provide some sort of relief. Using a technology or product to scratch the itch provide faster satisfaction that ignoring it. Once we come to depend on a tool, nothing else will do.

My answer to the vitamin versus painkiller question: Habit-forming technologies are both. These services seem at first to be offering nice-to-have vitamins, but once the habit is established, they provide an ongoing pain remedy.

Seeking pleasure and avoiding pain are two key motivators in all species.

...habit-forming products create associations in user’s minds—and that the solution to their pain may be found in your product’s use.

By progressing users through the four steps of the Hook Model—trigger, action, variable reward, and investment—hooks form habits.


  • For some businesses, forming habits is a critical component to success, but not every business requires habitual user engagement.
  • When successful, forming strong user habits can have several business benefits including: higher customer lifetime value (CLTV), greater pricing flexibility, supercharged growth, and a sharper competitive edge.
  • Habits cannot form outside the Habit Zone, where the behavior occurs with enough frequency and perceived utility.
  • Habit-forming products often start as nice-to-haves (vitamins) but once the habit is formed, they become must-haves (painkillers).
  • Habit-forming products alleviate user’s pain by relieving a pronounced itch.
  • Designing habit-forming products is a form of manipulation. Product builders would benefit from a bit of introspection before attempting to hook users to make sure they are building healthy habits, not unhealthy addictions...


If you are building a habit-forming product, write down the answers to these questions:

  • What habits does your business model require?
  • What problem are users turning to your product to solve?
  • How do users currently solve that problem and why does it need a solution?
  • How frequently do you expect users to engage with your product?
  • What user behavior do you want to make into a habit?

...new habits need a foundation upon which to build. Triggers provide the basis for sustained behavior change.

A trigger is the actuator of behavior...

Habit-forming technologies start changing behavior by first cueing users with a call to action.

External triggers are embedded with information, which tells the user what to do next.

An external trigger communicates the next action the user should take. Often, the desired action is made explicitly clear.

More choice require the user to evaluate multiple options. Too many choices or irrelevant options can cause hesitation, confusion, or worse—abandonment. Reducing the thinking required to take the next action increases the likelihood of the desired behavior occurring unconsciously.

Types of External Triggers

  1. Paid Triggers

Advertising, search engine marketing, and other paid channels are commonly used to get users’ attention and prompt them to act. Paid triggers can be effective but costly ways to keep users coming back. Habit-forming companies tend not to rely on paid triggers for very long, if at all.

  1. Earned Triggers

Earned triggers are free in that they cannot be bough directly, but they often require investment in the form of time spent on public and media relations. Favorable press mentions, hot viral videos, and featured app store placements are all effective ways to gain attention.

  1. Relationship Triggers

One person telling others about a product or service can be a highly effective external trigger for action. Whether through an electronic invitation, a Facebook “like”, or old fashioned word of mouth, product referrals from friends and family are often a key component of technology diffusion.

Relationship triggers can create the viral hyper-growth entrepreneurs and investors lust after.

  1. Owned Triggers

Owned triggers consume a piece of real estate in the user’s environment. They consistently show up in daily life and it is ultimately up to the user to opt in to allowing these triggers to appear.

As long as the user agrees to receive a trigger, the company that sets the trigger owns a share of the user’s attention.

Internal Triggers

When a product become tightly coupled with a thought, an emotion, or a preexisting routine, it leverages an internal trigger.

Internal triggers manifest automatically in your mind. Connecting internal triggers with a product is the brass ring of consumer technology.

Emotions, particularly negative ones, are powerful internal triggers and greatly influence our daily routines. Feelings of boredom, loneliness, frustration, confusion, and indecisiveness often instigate a slight pain or irritation and prompter’s and almost instantaneous and often mindless action to quell the negative sensation.

Positive emotions can also serve as internal triggers, and may even be triggered themselves by a need to satisfy something that is bothering us.

Gradually, these bonds cement into a habit as users turn to your product when experiencing certain internal triggers.

Once we’re hooked, using these products does not always require an explicit call to action. Instead, they rely upon our automatic responses to feeling that precipitate the desired behavior.

In the case of internal triggers, the information about what to do next is encoded as a learned association in the user’s memory.

New habits are sparked by external triggers, but associations with internal triggers are what keeps users hooked.

Products that successfully create habits soothe the user’s pain by laying claim to a particular feeling.

The ultimate goal of a habit-forming product is to solve the user’s pain by creating an association so that the user identifies the company’s product or service as the source of relief.

If you want to build a product that is relevant to folks, you need to put yourself in their shoes and you need to write a story from their side.

Dorsey believe a clear description of users—their desires, emotions, the context with which they use the product—is paramount to building the right solution.

...try asking the question “Why?” as many times as it takes to get an emotion. Usually, this will happen by the fifth why. This is a technique adapted from the Toyota Production System, described by Taiichi Ohno as the “5 Whys Method.” Ohno wrote that it was “the basis of Toyota’s scientific approach...by repeating ‘why?’ five times, the nature of the problem as well as its solution becomes clear.”

Fear is a powerful internal trigger.


  • Triggers cue the user to take action and are the first step in the Hook Model.
  • Triggers come in two types—external and internal.
  • External triggers tell the user what to do next by placing information within the user’s environment.
  • Internal triggers tell the user what to do next through associations stored in the user’s memory.
  • Negative emotions frequently serve as internal triggers.
  • To build a habit-forming product, makers need to understand which user emotions may be tied to internal triggers and know how to leverage external triggers to drive the user to action.


Refer to the answers you came up with in the last “Do This Now” section to complete the following exercises:

  • Who is your product’s user?
  • What is the user doing right before your intended habit?
  • Come up with three internal triggers that could cue your user to action. Refer to the 5 Whys Method...
  • Which internal trigger does your user experience most frequently?
  • Finish this brief narrative using the most frequent internal trigger and the habit you are designing: “Every time the user (internal trigger), he/she (first action of intended habit).”
  • Refer back to the question about what the user is doing right before the first action of the habit. What might be places and times to send an external trigger?
  • How can you couple an external trigger as closely as possible to when the user’s internal trigger fires?
  • Think of at least three conventional ways to trigger your user with current technology (e-mails, notifications, text messages, etc.). Then stretch yourself to come up with at least three crazy or currently impossible ideas for ways to trigger your user (wearable computers, biometric sensors, carrier pigeons, etc.). You could find that your crazy ideas spur some new approaches that may not be so nutty after all. In a few years new technologies will create all sorts of currently unimaginable triggering opportunities.


  • The second step in the Hook is action.
  • The action is the simplest behavior in anticipation of reward.
  • As described by Dr. B.J. Fogg’s Behavior Model:  For any behavior to occur, a trigger must be present at the same time as the user has sufficient ability and motivation to take action. To increase the desired behavior, ensure a clear trigger is present; next, increase ability by making the action easier to do; finally, align with the right motivator. Every behavior is driven by one of three Core Motivators: seeking pleasure and avoiding pain; seeking hope and avoiding fear; seeking social acceptance while avoiding social rejection. Ability is influence by the six factors of time, money, physical effort, brain cycles, social deviance, and non-routineness. Ability is dependent on users and their context at that moment.  
  • Heuristics are cognitive shortcuts we take to make quick decisions. Product designers can utilize many of the hundreds of heuristics to increase the likelihood of their desired action.


Refer to the answers you cam up with in the last “Do This Now” section to complete following exercises:

  • Walk through the path your users would take to use your product or service, beginning from the time they feel their internal trigger to the point where they receive their expected outcome. How many steps does it take before users obtain the reward they cam for? How does it compare with competing products and services?
  • Which resources are limiting your users’ ability to accomplish the task that will become habits?  Time Brain cycles (too confusing) Money Social deviance (outside the norm) Physical effort Non-routine (too new)  
  • Brainstorm three testable ways to make intended tasks easier to complete.
  • Consider how you might apply heuristics to make habit-forming action more likely.


  • Variable reward is the third phase of the Hook Model, and there are three types of variable rewards: the tribe, the hunt, and the self.
  • Rewards of the tribe is the search for social rewards fueled by connectedness with other people.
  • Rewards of the hunt is the search for material resources and information.
  • Rewards of the self is the search for intrinsic rewards of masters, competence, and completion.
  • When our autonomy is threatened, we feel constrained by our lack of choices and often rebel against doing a new behavior. Psychologists refer to this as reactance. Maintaining a sense of user autonomy is a requirement for repeat engagement.
  • Experiences with finite variability become increasingly predictable with use and lose their appeal over time. Experiences that maintain user interest by sustaining variability with use exhibit infinite variability.
  • Variable rewards must satisfy users’ needs while leaving them wanting to reengage with the product.


Refer to the answers you came up with in the last “Do This Now” section to complete the following exercises;

  • Speak with five of your customers in an open-ended interview to identify what they find enjoyable or encouraging about using your product. Are there any moments of delight or surprise? Is there anything they find particularly satisfying about using the product?
  • Review the steps your customer takes to use your product or service habitually. What outcome (reward) alleviates the user’s pain? is the reward fulfilling, yet leaves the user wanting more?
  • Brainstorm three ways your product might heighten users’ search for variable rewards using:  rewards of the tribe—gratification from others. rewards of the hunt—material goods, money, or information. rewards of the self—mastery, completion, competency, or consistency.  


  • The investment phase is the fourth step in the Hook Model.  Unlike the action phase, which delivers immediate gratification, the investment phase concerns the anticipation of rewards in the future.  
  • Investments in a product create preferences because of our tendency to overvalue our work, be consistent with past behaviors, and avoid cognitive dissonance.
  • Investment comes after the variable reward phase, when users are primed to reciprocate.
  • Investments increase the likelihood of users returning by improving the service the more it is used. They enable the accrual of stored value in the form of content, data, followers, reputation, or skill.
  • Investments increase the likelihood of users passing through the Hook again by loading the next trigger to start the cycle all over again.


Refer to the answers you came up with in the last “Do This Now” section to complete the following exercises:

  • Review your flow. What “bit of work” are your users doing to increase their likelihood of returning?
  • Brainstorm three ways to add small investments into your product to:  Load the next trigger. Store value as data, content, followers, reputation, and skill.  
  • Identify how long it takes for a “loaded trigger” to reengage your users. How can you reduce the delay to shorten time spent cycling through the Hook?


  • The Hook Model helps the product designer generate an initial prototype for a habit-forming technology. It also helps uncover potential weaknesses in an existing product’s habit-forming potential.
  • Once a product is built, Habit Testing helps uncover product devotees, discover which product elements (if any) are habit forming, and why those aspects of your product change user behavior. Habit Testing includes three steps: identify, codify, and modify.  First, dig into the data to identify how people are using the product. Next, codify these findings in search of habitual users. To generate new hypotheses, study the actions and paths taken by devoted users. Finally, modify the product to influence more users to follow the same path as your habitual users, and then evaluate results and continue to modify as needed.  
  • Keen observation of one’s own behavior can lead to new insights and habit-forming product opportunities.
  • Identifying areas where a new technology makes cycling through the Hook Model faster, more frequent, or more rewarding provides fertile ground for developing new habit-forming products.
  • Nascent behaviors—new behaviors that few people see or do, yet ultimately fulfill a mass market need—can inform future breakthrough habit-forming opportunities.
  • New interfaces lead to transformative behavior change and business opportunities.


  • Perform Habit Testing, as described...to identify the steps users take toward long-term engagement.
  • Be aware of your behaviors and emotions for the next week as you use everyday products. Ask yourself:  What triggered me to use these products? Was I prompted externally or through internal means? Am I using theses products as intended? How might these products improve their on-boarding funnels, reengage users through additional external triggers, or encourage users to invest in their services?  
  • Speak with three people outside your social circle to discover which apps occupy the first screen on their mobile devices. Ask them to use these apps as they normally would and see if you uncover any unnecessary or nascent behaviors.
  • Brainstorm five new interfaces that could introduce opportunities or threats to your business.


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