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

1. Seventy-nine percent of smartphone owners check their device within fifteen minutes of waking up every morning.1 Perhaps more startling, fully one-third of Americans say they would rather give up sex than lose their cell phones.

2. Cognitive psychologists define habits as “automatic behaviors triggered by situational cues”: things we do with little or no conscious thought.

3. Instead of relying on expensive marketing, habit-forming companies link their services to the users’ daily routines and emotions.7 A habit is at work when users feel a tad bored and instantly open Twitter.

4. Today, small start-up teams can profoundly change behavior by guiding users through a series of experiences I call hooks. The more often users run through these hooks, the more likely they are to form habits.

5. These years of distilled research and real-world experience resulted in the creation of the Hooked Model: a four-phase process companies use to form habits:

  1.  Trigger
  2. Action
  3. Variable Rewards
  4. Investment

6.  Trigger - A trigger is the actuator of behavior—the spark plug in the engine. 

7. 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 on a phone. For example, suppose Barbra, a young woman in Pennsylvania, happens to see a photo in her Facebook News Feed taken by a family member from a rural part of the state. It’s a lovely picture and because she is planning a trip there with her brother Johnny, the external trigger’s call to action (in marketing and advertising lingo) intrigues her and she clicks. 

8. By cycling through successive hooks, users begin to form associations with internal triggers, which attach to existing behaviors and emotions.

9. Action - Following the trigger comes the action: the behavior done in anticipation of a reward. The simple action of clicking on the interesting picture in her news feed takes Barbra to a Web site called Pinterest, a “social bookmarking site with a virtual pinboard.”

10. 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.

11. Variable Reward - What distinguishes the Hooked Model from a plain vanilla feedback loop is the Hook’s ability to create a craving.

12. Research shows that levels of the neurotransmitter dopamine surge when the brain is expecting a reward. Although dopamine is often wrongly categorized as making us feel good, introducing variability does create a focused state, which suppresses the areas of the brain associated with judgment and reason while activating the parts associated with wanting and desire. Although classic examples include slot machines and lotteries, variable rewards are prevalent in many other habit-forming products.

13. When Barbra lands on Pinterest, not only does she see the image she intended to find, but she is also served a multitude of other glittering objects.

14. Investment -The last phase of the Hooked Model is where the user does a bit of work. The investment phase increases the odds that the user will make another pass through the 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.

15. However, the investment phase isn’t about users opening up their wallets and moving on with their day. Rather, 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 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 Hooked Model.

16. 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.

17. Habit formation is good for business in several ways:

  • Increasing Customer Lifetime Value - User habits increase how long and how frequently customers use a product, resulting in higher Customer Lifetime Value.
  • Providing Pricing Flexibility - Buffett and his partner, Charlie Munger, realized that as customers form routines around a product, they come to depend upon it and become less sensitive to price. For example, in the free-to-play video game business, it is standard practice for game developers to delay asking users to pay money until they have played consistently and habitually.
  • Supercharging Growth - Users who continuously find value in a product are more likely to tell their friends about it.
  • Sharpening the Competitive Edge - User habits are a competitive advantage. Products that change customer routines are less susceptible to attacks from other companies. Products that require a high degree of behavior change are doomed to fail even if the benefits of using the new product are clear and substantial.
  • Building the Mind Monopoly - As one of its findings, the study concluded that the more frequently the new behavior occurred, the stronger the habit became. Like flossing, frequent engagement with a product—especially over a short period of time—increases the likelihood of forming new routines.

18. A company can begin to determine its product’s habit-forming potential by plotting two factors: frequency (how often the behavior occurs) and perceived utility (how useful and rewarding the behavior is in the user’s mind over alternative solutions).

19.Googling occurs multiple times per day, but any particular search is negligibly better than rival services like Bing. Conversely, using Amazon may be a less frequent occurrence, but users receive great value knowing they’ll find whatever they need at the one and only “everything store.”


21. Note that the line slopes downward but never quite reaches the perceived utility axis. Some behaviors never become habits because they do not occur frequently enough. No matter how much utility is involved, infrequent behaviors remain conscious actions and never create the automatic response that is characteristic of habits.

22. On the other axis, however, even a behavior that provides minimal minimal perceived benefit can become a habit simply because it occurs frequently.

23. It is worth noting that although some people use the terms interchangeably, habits are not the same things as addictions. The latter describes persistent, compulsive dependencies on a behavior or substance that harms the user. Addictions, by definition, are self-destructive.

24. A habit, on the other hand, is a behavior that can have a positive influence on a person’s life.

25.Habit-forming products often start as nice-to-haves (vitamins) but once the habit is formed, they become must-haves (painkillers).

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

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

28. More choices require the user to evaluate multiple options. Too many choices or irrelevant options can cause hesitation, confusion, or worse—abandonment.4 Reducing the thinking required to take the next action increases the likelihood of the desired behavior occurring with little thought.

29. Companies can utilize four types of external triggers to move users to complete desired actions:

 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. Because paying for reengagement is unsustainable for most business models, companies generally use paid triggers to acquire new users and then leverage other triggers to bring them back.

Earned Triggers - Earned triggers are free in that they cannot be bought 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.

Relationship Triggers - One person telling others about a product or service can be a highly effective external trigger for action.

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. For example, an app icon on the user’s phone screen, an e-mail newsletter to which the user subscribes, or an app update notification only appears if the user wants it there. As long as the user agrees to see the trigger, the company that sets the trigger owns a share of the user’s attention.

30. Companies may be lulled into thinking that related downloads or sales spikes signal long-term success, yet awareness generated by earned triggers can be short-lived.

31. Yet external triggers are only the first step. The ultimate goal of all external triggers is to propel users into and through the Hooked Model so that, after successive cycles, they do not need further prompting from external triggers.

32. When users form habits, they are cued by a different kind of trigger: internal ones.

33. When a product becomes tightly coupled with a thought, an emotion, or a preexisting routine, it leverages an internal trigger. Unlike external triggers, which use sensory stimuli like a morning alarm clock or giant “Login Now” button, you can’t see, touch, or hear an internal trigger.

34. Internal triggers manifest automatically in your mind. Connecting internal triggers with a product is the brass ring of habit-forming technology.

35. 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 prompt an almost instantaneous and often mindless action to quell the negative sensation. For instance, Yin often uses Instagram when she fears a special moment will be lost forever.

36. The study demonstrated that people suffering from symptoms of depression used the Internet more. Why is that? One hypothesis is that those with depression experience negative emotions more frequently than the general population and seek relief by turning to technology to lift their mood.

37. Products that successfully create habits soothe the user’s pain by laying claim to a particular feeling. To do so, product designers must know their user’s internal triggers—that is, the pain they seek to solve.

38. 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.

39. “[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. So, we spend a lot of time writing what’s called user narratives.”

40. Dorsey believes a clear description of users—their desires, emotions, the context with which they use the product—is paramount to building the right solution. In addition to Dorsey’s user narratives, tools like customer development,11 usability studies, and empathy maps12 are examples of methods for learning about potential users.

41.  One method is to try asking the question “Why?” as many times as it takes to get to 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.”

42. 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.

43. If action is paramount to habit formation, how can a product designer influence users to act? Is there a formula for behavior? It turns out that there is.

44. Fogg posits that there are three ingredients required to initiate any and all behaviors: (1) the user must have sufficient motivation; (2) the user must have the ability to complete the desired action; and (3) a trigger must be present to activate the behavior.

45. The Fogg Behavior Model is represented in the formula B = MAT, which represents that a given behavior will occur when motivation, ability, and a trigger are present at the same time and in sufficient degrees.

46. Fogg states that all humans are motivated to seek pleasure and avoid pain; to seek hope and avoid fear; and finally, to seek social acceptance and avoid rejection.

47. Consequently, any technology or product that significantly reduces the steps to complete a task will enjoy high adoption rates by the people it assists.

48. Evan Williams, cofounder of Blogger, Twitter, and Medium, echoes Hauptly’s formula for innovation when he describes his own approach to building three massively successful companies: “Take a human desire, preferably one that has been around for a really long time … Identify that desire and use modern technology to take out steps.”

49. Fogg describes six “elements of simplicity”—the factors that influence a task’s difficulty. These are: 

  • Time—how long it takes to complete an action. 
  • Money—the fiscal cost of taking an action. 
  • Physical effort—the amount of labor involved in taking the action. 
  • Brain cycles—the level of mental effort and focus required to take an action. 
  • Social deviance—how accepted the behavior is by others.
  • Non-routine—according to Fogg, “How much the action matches or disrupts existing routines.”

50. The action phase of the Hooked Model incorporates Fogg’s six elements of simplicity by asking designers to consider how their technology can facilitate the simplest actions in anticipation of reward. The easier an action, the more likely the user is to do it and to continue the cycle through the next phase of the Hooked Model.

51. After uncovering the triggers that prompt user actions and deciding which actions you want to turn into habits, you can increase motivation and ability to spark the likelihood of your users taking a desired behavior. But which should you invest in first, motivation or ability? Where is your time and money better spent? The answer is always to start with ability.

52. Naturally, all three parts of B = MAT must be present for a singular user action to occur; without a clear trigger and sufficient motivation there will be no behavior. However, for companies building technology solutions, the greatest return on investment generally comes from increasing a product’s ease of use.

53. The fact is, increasing motivation is expensive and time consuming. Web site visitors tend to ignore instructional text; they are often multitasking and have little patience for explanations about why or how they should do something. Influencing behavior by reducing the effort required to perform an action is more effective than increasing someone’s desire to do it. Make your product so simple that users already know how to use it, and you’ve got a winner.

54. There are many counterintuitive and surprising ways companies can boost users’ motivation or increase their ability by understanding heuristics—the mental shortcuts we take to make decisions and form opinions.

55. The Scarcity Effect - The appearance of scarcity affected their perception of value.

56. The Framing Effect - Context also shapes perception. In a social experiment, world-class violinist Joshua Bell decided to play a free impromptu concert in a Washington, D.C., subway station. Bell regularly sells out venues such as the Kennedy Center and Carnegie Hall for hundreds of dollars per ticket, but when placed in the context of the D.C. subway, his music fell upon deaf ears. 

57. Almost nobody knew they were walking past one of the most talented musicians in the world. The mind takes shortcuts informed by our surroundings to make quick and sometimes erroneous judgments.

58. The Anchoring Effect - People often anchor to one piece of information when making a decision.

59. The Endowed Progress Effect - Two groups of customers were given punch cards awarding a free car wash once the cards were fully punched. One group was given a blank punch card with eight squares; the other was given a punch card with ten squares that came with two free punches. Both groups still had to purchase eight car washes to receive a free wash; however, however, the second group of customers—those that were given two free punches—had a staggering 82 percent higher completion rate.

60. The study demonstrates the endowed progress effect, a phenomenon that increases motivation as people believe they are nearing a goal.

61. The third step in the Hooked Model is the variable reward phase, in which you reward your users by solving a problem, reinforcing their motivation for the action taken in the previous phase.

62. The study revealed that what draws us to act is not the sensation we receive from the reward itself, but the need to alleviate the craving for that reward.

63. In the 1950s psychologist B. F. Skinner conducted experiments to understand how variability impacted animal behavior.

64. First, Skinner placed hungry pigeons inside a box rigged to deliver a food pellet to the birds every time they pressed a lever. Similar to Olds’s and Milner’s lab mice, the pigeons learned the cause-and-effect relationship between pressing the lever and receiving the food.

65. In the next part of the experiment Skinner added variability. Instead of providing a pellet every time a pigeon tapped the lever, the machine discharged food after a random number of taps. Sometimes the lever dispensed food, other times not. Skinner revealed that the intermittent reward dramatically increased the number of times the pigeons tapped the lever. Adding variability increased the frequency of the pigeons’ completing the intended action.

66. Variable rewards can be found in all sorts of products and experiences that hold our attention. They fuel our drive to check e-mail, browse the web, or bargain-shop. I propose that variable rewards come in three types: the tribe, the hunt, and the self.

67. Rewards of the Tribe - We are a species that depends on one another. Rewards of the tribe, or social rewards, are driven by our connectedness with other people. Our brains are adapted to seek rewards that make us feel accepted, attractive, important, and included.

68. Sites that leverage tribal rewards benefit from what psychologist Albert Bandura called “social learning theory.”8 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.

69. Here are some online examples of rewards of the tribe:

  • “Likes” and comments offer tribal validation for those who shared the content, and provide variable rewards that motivate them to continue posting.
  • Stack Overflow devotees write responses in anticipation of rewards of the tribe. Each time a user submits an answer, other members have the opportunity to vote the response up or down. The best responses percolate upward, accumulating points for their authors
  • League of Legends, a popular computer game, launched in 2009 and quickly achieved tremendous success. Soon after its launch, however, the game’s owners found they had a serious problem: The online video game was filled with “trolls”—people who enjoyed bullying other players while being protected by the anonymity the game provides. To combat the trolls, the game creators designed a reward system leveraging Bandura’s social learning theory, which they called Honor Points. The number of points earned was highly variable and could only be conferred by other players. Honor Points soon became a coveted marker of tribe-conferred status and helped weed out trolls by signaling to others which players should be avoided.

70. The need to acquire physical objects, such as food and other supplies that aid our survival, is part of our brain’s operating system.

71. Here are a few examples of products that create habits by leveraging rewards of the hunt:

  • Slot machines provide a classic example of variable rewards of the hunt. Gamblers plunk $1 billion per day into slot machines in American casinos, which is a testament to the machines’ power to compel players.16 By awarding money in random intervals, games of chance entice players with the prospect of a jackpot. Naturally, winning is entirely outside the gambler’s control—yet the pursuit can be intoxicating.
  • The Twitter timeline, for example, is filled with a mix of both mundane and relevant content. This variety creates an enticingly unpredictable user experience. On occasion a user might find a particularly interesting piece of news, while other times she won’t. To keep hunting for more information, all that is needed is a flick of the finger or scroll of a mouse. Users scroll and scroll and scroll to search for variable rewards in the form of relevant tweets.

72. We are driven to conquer obstacles, even if just for the satisfaction of doing so. Pursuing a task to completion can influence people to continue all sorts of behaviors.

73. Surprisingly, we even pursue these rewards when we don’t outwardly appear to enjoy them. For example, watching someone investing countless hours into completing a tabletop puzzle can reveal frustrated face contortions and even sounds of muttered profanity.

74. The rewards of the self are fueled by “intrinsic motivation” as highlighted by the work of Edward Deci and Richard Ryan. Their self-determination theory espouses that people desire, among other things, to gain a sense of competency. Adding an element of mystery to this goal makes the pursuit all the more enticing.

75. Rewards of the self are a defining component in video games, as players seek to master the skills needed to pursue their quest. Leveling up, unlocking special powers, and other game mechanics fulfill a player’s desire for competency by showing progression

76. Variable rewards are not magic fairy dust that a product designer can sprinkle onto a product to make it instantly more attractive. Rewards must fit into the narrative of why the product is used and align with the user's internal triggers and motivations. They must ultimately improve the user's life.

77. To change behavior, products must ensure the users feel in control. People must want to use the service, not feel they have to.

78. Experiences with finite variability become less engaging because they eventually become predictable.

79. For example, games played to completion offer finite variability, while those played with other people have higher degrees of infinite variability because the players themselves alter the gameplay throughout.

80. The more users invest time and effort into a product or service, the more they value it. In fact, there is ample evidence to suggest that our labor leads to love.

81. The more effort we put into something, the more likely we are to value it; we are more likely to be consistent with our past behaviours; and finally, we change our preferences to avoid cognitive dissonance.

82. The last step of the Hooked Model is the investment phase, the point at which users are asked to do a bit of work. Here, users are prompted to put something of value into the system, which increase the likelihood of their using the product and of successive passes through the cycle.

83. Unlike in the action phase of the Hook, investments are about the anticipation of longer-term rewards, not immediate gratification.

84.In Twitter, for example, the investment comes in the form of following another user. There is no immediate reward for following someone, no stars or badges to affirm the action. Following is an investment in the service, which increases the likelihood of the user checking Twitter in the future.

85. Also in contrast to the action phase, the investment phase increase friction. This certainly breaks conventional thinking in the product design community that all user experiences should be as easy and effortless as possible. In the investment phase, however, asking users to do a bit of work comes after users have received variables rewards, not before. The timing of asking for user investment is critically important. 

86. The collection of memories and experiences, in aggregate, becomes more valuable over time and the service becomes harder to leave as users' personal investment in the site grows.

87. The company found that the more information users invested in the site, the more committed they became to it.

88. Reputation makes users, both buyers and sellers, more likely to stick with whichever service they have invested their efforts in to maintain a high-quality score.

89. Investing time and effort into learning to use a product is a form of investment and stored value. Once a user has acquired a skill, using the service becomes easier.

90. Once users have invested the effort to acquire a skill, they are less likely to switch to a competing product.

91. I recommend that you progressively stage the investment you want from users into small chucks of work, starting with small, easy tasks and building up to harder tasks during successive cycles through the Hooked Model.

92. Users set future triggers during the investment phase, providing companies with an opportunity to reengage the user.

93. You are now equipped to use the Hooked Model to ask yourself these fundamental questions for building effective hooks:

What do users really want? What pain is your product relieving? (Internal trigger) 

What brings users to your service? (External trigger) 

What is the simplest action users take in anticipation of reward, and how can you simplify your product to make this action easier? (Action) A

re users fulfilled by the reward yet left wanting more? (Variable reward) What “bit of work” do users invest in your product? 

Does it load the next trigger and store value to improve the product with use? (Investment)

94. Creating a product that the designer does not believe improves users' lives and that he himself would not use is called exploitation.

95. Start-ups are grueling and only the most fortunate persevere before finding success. If you only build for fame or fortune, you will likely find neither. Build for meaning, though, and you can’t go wrong.

96. The Hooked Model can be a helpful tool for filtering out bad ideas with low habit potential as well as a framework for identifying room for improvement in existing products.

97. Building a habit-forming product is an iterative process and requires user-bebavior analysis and continuous experimentation.

98. Habit Testing offers insights and actionable data to inform the design of habit-forming products. It helps clarify who your devotees are, what parts(if any) of your product are habit forming, and why those aspects of your product are changing user behavior.

99. Habit Testing:

  • Step 1 - Identify. First define what it means to be a devoted user. How often "should" one use your product? Publicly available data from similar products or solutions can help define your users and engagement targets. Educated assumptions must be made if data is not available.
  • Step 2 -Codify. Atleast 5% of your users should be habitual users initially. Once your exceed this bar, the next step is to codify the steps they took using your product to understand what hooked them. You are looking for a Habit Path -- a series of similar actions shared by your most loyal users. For example, in its early days, Twitter discovered that once new users followed thirty other members, they hit a tipping point that dramatically increased the odds they would keep using the site.
  • Step 3 - Modify. Armed with new insights, it is time to revisit your product and identify ways to nudge new users down the same Habit Path taken by devotees.

100. Identifying areas where a new technology makes cycling through the Hooked Model faster, more frequent, or more rewarding provides fertile ground for developing new habit-forming products.