Book Notes by Abi Noda

Hooked by Nir Eyal

ISBN: 1494277530
READ: Apr 10, 2014

Critical Summary

Why is it that apps like Facebook and Instagram are so popular? Why does email dominate our lives? What does it take to create products that are similarly habit-forming and successful?

Eyal lays out a simple framework called the "hooked cycle" which consists of four parts: trigger, action, variable reward, and investment.

Trigger - What are users feeling and doing the moment before they would use your product? What is the emotional need they are solving with your product? Facebook, for example, relieves us of the feeling of wanting to belong and be important to others. Email relieves us of uncertainty and staying connected. Understanding these questions is the basis for designing good customer acquisition and re-engagement strategies (eg. email notifications).

Action - For a product to be sticky, it has to be simple and easy to use so that there are no barriers to adoption and usage. While we can also try to motivate users to complete actions, it's easier and usually more effective to reduce the effort it requires.

Variable Reward - Providing variable rewards after actions keeps users excited and motivated to keep on using and returning to your product. The three types of rewards are (1) material (eg. saving money), (2) social (eg. feeling accepted or important), and (3) completion (eg. clearing out your inbox).

Investment - Humans place more value on things they've committed their own labor to. Thus sticky products should become more valuable over time based on whats been put in the user (eg. amassing followers on Twitter).

Overall, the book reads easily but sometimes feels like its bouncing around a bit, leading you astray from the main points. The book also contains simple checklists in each chapter that you can apply to your own work. Not all products and business will benefit from this book–it's great for consumer technology companies that want to increase customer engagement and retention.


habit = frequency + perceived utility

hooked cycle = trigger, action, variable reward, investment

Benefits of "addictive" products = viral growth, increased CLTV, lower price sensitivity, customer loyalty.

For a new behavior to take hold, it must occur often. The more frequently engagement with a product occurs, the stronger a habit it forms. For an infrequent action to become a habit, the user must perceive a high degree of utility, either from gaining pleasure or avoiding pain.

Recall the SCARF model + theory of potential loss from Influence: we are more motivated by the thought of losing something than by the thought of gaining something of equal value, eg. homeowners who are told how much they could lose from inadequate insulation are more likely to insulate their homes than those told how much money they could save

Habit-forming products often start as nice-to-haves, but once the habit is formed, they become must-haves. Think of Facebook, Instagram, Pinterest...

1. Trigger

Habits are sparked by external triggers (eg. an ad), but associations with internal triggers keep are what keep users hooked.

Build external triggers for on-boarding users. Design around internal triggers for satisfying and retaining users.

The goal of a habit-forming product is to create an association with a person's pain so as to become the go-to source of relief.

Negative emotion are powerful internal triggers — eg. boredom, loneliness, frustration, confusion, indecisiveness all instigate pain and prompt an almost instantaneous and mindless action to quell the negative sensation.

Our life is filled with tiny stressors and we're usually unaware of our habitual reactions to these nagging issues. Technology provides psychological relief.

Similar concepts as fixed-action patterns discussed in Influence. Fixed-action patterns in humans are built through conditioning.

People suffering from symptoms of depression use the Internet more, perhaps because they experience negative emotions more frequently and seek relief by turning to technology to lift their mood.

Common human needs are timeless and universal.

For practice, study the drivers behind successful habit-forming products to understand how they solve user's problems. eg. Instagram leads with an external triggers such as an invite/recommendation from a friend, press, the app icon on a user's phone. It addresses emotional pains such as boredom, FOMO, and validating one's status.

Answer: What do your users want to achieve by using your solution? Where and when will they use it? What emotions influence their use and will trigger them to action?

Asking people will not reveal these wants since they themselves don't know which emotions motivate them. What they say they want is different from what they actually do.

Methodologies (customer development, positioning statements, empathy maps are mentioned but not emphasized):


Do this:

2. Action

Fogg Behavior Model: A behavior will occur when motivation, ability, and a trigger are present at the same time and in sufficient degrees.

eg. If your cell phone rings but its in your bag, your inability to easily answer inhibited the action. If you thought the caller was a telemarketer, your lack of motivation inhibited the action.

To increase the desired behavior, ensure a clear trigger is present, then increase the ability by making the action easier to do, and finally align with the right motivator.

Between motivation and ability, ability (ease-of-use) has the greatest ROI. Influencing behavior by reducing the effort required to perform an action is more effective than increasing someone's desire to do it. Altering motivation is more difficult and expensive.

"Make your product so simple that your users already know how to use it"

Three core motivators: seek pleasure / avoid pain, seek hope / avoid fear, seek social acceptance / avoid rejection.

This is a simplistic description. Made to Stick and the SCARF model have better examples.

Heuristics are cognitive shortcuts we take to make quick decisions: scarcity effect, framing (eg. people perceive more expensive products to be better), anchoring, endowed progress effect (eg. profile completion on linked in)

Reference Influence

Any technology or product that significantly reduces the steps to complete a task will enjoy high adoption rates.

Evan Williams: "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."

Facebook, Twitter, and Instagram make content creation / self-expression easy.

Focus on simplicity as a function of the user's scarcest resource at the moment. What is making it difficult for the user to accomplish the desired action? Is the user short on time? Is the behavior too expensive? Is the product or process too difficult to understand? Is the user in a social context where the behavior could be perceived as inappropriate? Is the behavior so far outside of the user's normal routine that its strangeness is off-putting?

3. Variable Reward

Reward your users for their behavior, reinforcing their motivation for the action taken in the previous phase.

Studies of the brain reveal 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.

Without variability, we are like children in that once we figure out what will happen next, we become less excited by the experience. Variability increases the frequency of us performing the actions.

This is why checking personal investments is much more exciting than checking a bank account.

Three types of variable rewards:

  1. Tribe - The search for social rewards that make us feel accepted, attractive, important, and included. eg. Facebook likes and comments offer tribal validation for those who shared the content, and provide variable rewards that motivate them to continue posting.

  2. Hunt - The search for material resources and information, eg. gambling machines, twitter feeds of relevant articles

  3. Self - The search for intrinsic rewards of mastery, competence, and completion. We are driven to conquer obstacles solely for the satisfaction of doing so, eg. table puzzles.

Habit-forming products offer one or more variable reward types, eg. email = social reward, opportunities/threads to livelihood, and completion.

Variable rewards are not fairy dust – only by understanding what matters to users can a company match the right variable reward to their intended behavior (eg. tried monetary reward for Q&A, vs Quora which used social reward)

Rewards must fit into the narrative of why the product is used and align with the user's internal triggers and motivations

We are more likely to be persuaded when our ability to choose is reaffirmed. A meta-analysis of 42 studies involving over 22,000 participants concluded that the words "but you are free to accept or refuse" double the likelihood of people saying yes.

I should start using this.

Experiences with finite variability become increasing predictable with use and lose appeal over time (eg. watching 24 gets old after awhile)

4. Investment

Small investments change our perceptions, turning unfamiliar actions into everyday habits.

Humans irrationally overvalue our own work.

The book references several examples from the "Commitment and Consistency" section in Influence

Prompt users to put something of value into the system. Investments are about anticipation of longer-term rewards, not immediate gratification, eg. following someone on Twitter, filling out your LinkedIn profile.

Prompt for the investment after the reward to capitalize on reciprocity.

The key is to leverage the user's understanding that the service will get better with use and personal investment.

Investment == stored value.

Stickiest forms = followers, reputation (eg. Yelp, AirBnB), mastery (eg. photoshop)

Todo-list app gives you clear, easy-to-follow instructions and a variable reward in the form of a congratulatory message and satisfaction of mastering the app. Then they're asked to connect the app to their calendar and give the app permission to send a notification after their next meeting, which prompts users to return to the app.

Applying the Hook Model

  1. What do users really want? What pain is your product relieving? (Internal Trigger)
  2. What brings users to your service? (External Trigger)
  3. What is the simplest action users take in anticipation of reward, and how can you simplify your product to make this action easier? (Action)
  4. Are users fulfilled by the reward, yet left wanting more? (Variable Reward)
  5. 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)

The Hook model is about changing people's behaviors and build persuasive products.