Hooked is an eye-opening book that provides the framework for building habit-forming products.

I had grown weary of the slew of ethically questionable, addictive products that are dominating the marketplace. With Hooked I hoped to wrap my head around how companies create deeply-rooted habits in their users. I don’t think I had thought any further than that. Certainly, I wasn’t hoping to apply the knowledge in the book. Instead, I was looking for confirmation that I should find a different job! But, I found a great deal of useful and applicable information with Hooked.

Hooked From The Start

The Hook Model is the foundational point of the book above which all else is built.

There are four steps to the Hook Model: trigger, action, variable reward, and investment.


Hooked: The Hook Model
The Hook Model



A trigger is anything that impacts behavior. There are two types of trigger: external and internal. All products must first attempt to trigger users externally and then move toward triggering them internally one a habit is built.



Triggers convince us that we may be rewarded if we act. This is our impetus. In order to increase the likelihood of action, companies focus on reducing friction and increasing motivation.


Variable Reward

In order to get users addicted to your product, you must ensure it’s somewhat unpredictable. Research shows that levels of the neurotransmitter dopamine surge when the brain is expecting a reward. Providing variability dramatically increases the amount of dopamine released, as well as suppressing the pre-frontal cortex (associated with judgment and reason) while activating the limbic system (associated with desires).



The investment phase increases the likelihood that a user will once again travel through a Hook cycle. Investment can come in the form of time, effort, social capital, or money. But regardless of form, any user investment should improve the product or service. Inviting friends, stating preferences, and mastery are all investments the user makes to improve their experience.


A World of Addicts


Hooked: Phone Addiction
Phone Addiction

As the world becomes more connected and companies collect dizzying amounts of information on customers, the potential for ever more addictive products rises. And as the products we use get more addictive, we become more addicted. In order to thrive, we must have restrictions in place that ensure only ethical, habit-forming products – products that nudge us to live better lives – are allowed to influence how we live.

A Definition of the Hook

Hooks connect the user’s problem with a company’s solution frequently enough o create a habit.

A Word on Pricing Flexibility

“You can determine the strength of a business over time by the amount of agony they go through in rising prices.” – Warren Buffet

As a customer develops routines around a product, they come to depend on it and are less price sensitive.

An example of this: in freemium video games, it’s common practice to delay asking users to pay until they play habitually. Once hooked, turning users into paying customers is much easier.


A Blueprint for Growth

Products with higher user engagement stand to grow faster than rivals as die-hard fans spread the word for free. “More frequent usage drives more viral growth.”

Viral Cycle Time is the amount of time it takes for one user to successfully invite another user. A shorter cycle time compounds virality over time in the same way financial investments compound.


The Fallacy of Marginally Better

Entrepreneurs often create products slightly better than the competition and hope this will be enough to lure customers away from established products. But this ignores a few things: investment, reputation, connection, habitualisation. For your product to attract customers away from alternative products, it must be so good that users are willing to let go of something which they have invested considerably in. They must throw away their built reputation, say goodbye to all the friends using the old product, and go from doing something automatically (nothing easier than automatic) to doing something consciously. That’s a big ask!

Can I Have Some Change, Please?

Products that require a high degree of behavior change are doomed to fail.

Experiments on lab animals show that newly habituated behaviors tend to give way to first learned behaviors. This is because even when our routines change, neural pathways to our old habits remain active in the brain. “The habits you’ve most recently acquired are also the ones most likely to go soonest.”

The more frequently a new behavior occurs, the more likely it is to stick around.



It is possible for infrequent actions to become habitual. This requires a high degree of utility, either from gaining pleasure or avoiding pain. The greater the utility the lower the frequency of use can be while still creating habits, and vice versa.

However, some behaviors never become habits because they occur so infrequently, remaining conscious actions. We need automatic responses. Conversely, a behavior proving little benefit can become a habit simply due to high frequency.

A Note On Building Habits

“A 2010 study found that some habits can be formed in a matter of weeks while others can take more than 5 months!” The complexity of the behavior and how important it is to the individual in question greatly affects how quickly a routine is built.

Vitamins And Painkillers

Evidence shows that taking multivitamins may actually be doing more harm than good! *this was pretty mind-blowing for me. I looked into it and, as far as I can tell, there is a legitimate reason to believe you should ditch your multivitamin (as I have now done.)

Hooked goes on to say we don’t take vitamins for efficacy’s sake. Rather, we do it to say we’ve done it – it provides a psychological boost rather than any noticeable physical one.

This is opposed to painkillers, where there is a noticeable and immediate effect.

Hooked suggests that products are like Vitamins or Painkillers. Painkillers relieve a specific pain and have quantifiable markets. Vitamins do not necessarily solve anything tangible. Instead, they appeal to users’ emotional needs. Investors look for Painkillers, apparently.

Painkillers Playing Dressup

Nir Eyal stipulates that despite many of today’s most addictive products appearing to be vitamins, they are really painkillers masked as vitamins – things we didn’t know we needed until they become an intrinsic part of our lives. Then they provide relief – in the form of distraction – from our boring, unfulfilling lives

*I think this part of the book is fluffy/pointless, and I would have left it out if not for wanting desperately to include the multivitamin inefficacy. And I couldn’t do that without some context!*


External Triggers

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

Here we want to reduce the thinking required to take the next action by reducing the choice and thereby increasing the likelihood of the desired behavior occurring unconsciously.

Types Of External Triggers

Paid triggers

Advertising. Effective but costly.

Earned Triggers

Favourable press mentions, viral videos, and featured app placements. Awareness generated by earned triggers can be short-lived. In order for earned triggers to drive ongoing customer acquisition, companies must keep their products in the limelight – a challenging task.

Relationship Triggers

Product referrals from friends can create viral growth. Requires building an engaged user base that is excited to share the benefits of your product.

Owned Trigger

“Owned triggers consume a piece of real estate in the user’s environment.” App icons, email newsletters, and notifications are all examples. As long as the user remains opted in, the company owns a share of the user’s attention.

Unlike paid, earned, and relationship owned triggers don’t just drive new user acquisition, they also prompt repeat use until a habit is formed. This should be the focus of any product looking to make users hooked.

Internal Triggers

Products that are coupled with a thought, emotion or preexisting routine are leveraging an internal trigger. They automatically manifest in your mind with no need for prompting. This is dissimilar to external triggers which use sensory stimuli.


Depression and Internet Usage

A study at the Missouri University of Science and Technology identified that students with depressive symptoms tended to consume far larger amounts of video, games, social media, and email than their non-depressed counterparts. In order to combat their frequent negative emotions, they seek relief in the form of technology.        

Building Triggers

“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 a source of relief.”

Be aware that people’s declared differences are extremely different from their revealed preferences.

Really try to get into the mind of your user: what underwear do they wear? Are they comfortable farting in public? etc.

A clear description of users is essential to building a relevant product. One technique for better understanding your users is to ask “why?” until you get to a base emotion – fear, sadness, anger, happiness etc.


The more effort required to perform an action, the less likely it is to occur.

There are three ingredients required to initiate any and all behaviors: sufficient motivation, the ability to complete the action, and a trigger.

*Here Hooked explains motivation which I think is somewhat unnecessary, therefore I’m going to move straight onto ability.*


First, understand why people use a product or service. Next, lay out the steps necessary to complete the task. Finally, start removing steps until you reach the simplest possible process. Only tasks that are simple to complete (at least relative to the competition) stand a chance. According to Hooked, ease of use is the greatest return on investment.

*Nir Eyal then talks about heuristics – scarcity bias, the framing effect, the anchoring effect, and endowed progress – and their impact on motivation. These are four of 166 cognitive biases – all of which are definitely worth learning about if you want to increase sales, improve your relationships, and better understand and control your own behavior. However, I think it would be best to go to the source when learning about these biases, rather than reading Hooked’s summary. *


Hooked On Variable Rewards


Hooked: The Variable Rewards of Gambling
The Variable Rewards of Gambling


“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.” To hold our attention over the long-term, however, products must have an ongoing degree of novelty.

Variable rewards utilize the tribe, the hunt, or the self.

Rewards Of The Tribe

“Our brains are adapted to seek rewards that make us feel accepted, attractive, important, and included.”

This adaptation makes us crave social validation. In fact, studies have shown that people who observe someone being rewarded for a particular behavior are more likely to alter their own beliefs and behaviors so that they too receive the reward.

Rewards Of The Hunt

For 2 million years prior to the invention of handcrafted weapons, humans hunted animals by

chasing them down over many hours until they became exhausted and keeled over, accepting their time was over (read more here). In order to run down animals far faster than us, we had to be motivated to pursue with the hope that at some point we will catch up with what we desire. This is what now motivates us to chase after that promotion or to keep saving until we can purchase those sweet Kurt Geiger shoes.

Rewards Of The Self

We are strongly motivated to gain competency. We chemically reward ourselves as we become more experienced and skilled.

Considerations In Designing Reward Systems

“Only by understanding what truly matters to users can a company correctly match the right variable reward to their intended behavior…When there is a mismatch between a consumer’s problem and the company’s solution, no amount of rewards will spur engagement.”

Our Need For Autonomy

We are more likely to be persuaded when our ability to choose is reaffirmed. Too many companies build products hoping users will do what they make them do instead of what they want to do. The moral here is: make your product enjoyable, easy to use, and attractive or users will return to their old habits. Understand human psychology and work with it, rather than against it.

Beware of Finite Variability

Experiences with finite variability become less engaging and they become predictable. Content creation is infinitely variable. Products with finite variability must constantly reinvent themselves to keep users’ attention.




Escalation of Commitment

The more users invest time and effort into a product or service, the more they value it. A study by Dan Ariely, Michael Norton, and Daniel Motion measured the effect of labor on how people value things. They were given instructions to assemble origami and then attach a monetary value to their piece. They valued their own pieces almost as high as an independent group valued expert-made origami.

Need For Consistency

If we invest in something once we are far more likely to invest again. We do not like to think of ourselves as fools, so we justify past behavior by staying consistent.

We Avoid Cognitive Dissonance

This is the irrational manipulation of reality to reconcile conflicting ideas so that we are better able to deal. This leads us to change our preferences to avoid the continued conflict of ideas, saying something like ‘I never really liked playing football anyway. Much prefer watching. Just took a broken back for me to realize it.’

Stored Value

“The stored value users put into the product increases the likelihood they will use it again in the future and comes in a variety of forms… 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.”

As users make changes to their experience of a product or service so that it caters more specifically to their needs (by adding information, following etc.), the product becomes more and more valuable.


Users are more likely to stick with whichever service they have invested their efforts in to maintain a good reputation. Reputation manifests itself as a number of followers or as a rating.


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

The Next Trigger

Ultimately, companies want their product to rely on internal triggers to drive product use, though, to begin with, users must go through multiple cycles of the Hook Model. Therefore, external triggers must be used to bring users back to start of another cycle. “Habit-forming technologies leverage the user’s past behavior to initiate an external trigger in the future.”

*Here Nir Eyal offers multiple companies that are exemplary of loading the next trigger. I’ve included only one as it’s the most interesting and the others merely repeat its sentiment.


In Snapchat, users pass through the investment phase of the Hook Model each time they send a selfie, doodle, or message. Each photo or video sent contains an implicit prompt to respond. Responding to photos/videos is made incredibly easy – just tap twice on the original message. Finally, the transitory nature of messages encourages timely responses, creating a back-and-forth that quickly leads people to become hooked.


The Manipulation Matrix

Manipulation Matrix


This chapter is an essential one that goes into the ethics of causing addiction in customers. However, it is far too lenient – even encouraging – of companies such as Facebook and Twitter, under-representing their negative impact on relationships, mental health, and users’ ability to do deep work. Highly addictive and almost entirely worthless products.    

The Facilitator

“When you create something that you would use, that you believe makes the user’s life better, you are facilitating a healthy habit.”

“It’s important to recognize that the percentage of users who form detrimental dependency is very small.” This seems to have been plucked from thin air. You only have to look around to see that how addicted we all are to our phones with all the apps and notifications and messages that demand our attention. I think the below image (taken from an incredible article on Hackernoon. Check it out here) showing the average amount of years spent on social media says it all.



We're All Hooked
A Lifetime Of Social Media


Hardly Any Addicts Don’t Exist!

“Though the world is becoming a potentially more addictive place, most people have the ability to self-regulate their behaviors.”

This is completely farcical. It’s not potentially a more addictive place, it is undoubtedly an astronomically addictive place. Simply comparing the life of a tribesman – where everything had to be worked for and where addictive substances were hard to come by and addictive products and services were entirely non-existent — and to a millennial is enough to show how drastically more addictive the world is becoming. And to say that most people can self-regulate their behaviors is also ungrounded. Maybe in Nir Eyal’s circle of highly educated, wealthy friends, this is the case. But to extrapolate from this fringe group some general truth is juvenile. In fact, at some point in the book Nor admits he is addicted to his phone.

This left section really left a bad taste in my mouth. This was Hooked’s opportunity to provide a moral compass for its readers to look up to, but Nir Eyal decided to take a pass on this opportunity and instead provide platitudes.

However, the definitions remain useful guides. Essentially, focus on being a facilitator.

The Peddler

“The Peddler has a strong desire to improve the lives of their users, but when pressed they admit they would not actually use their own creations.” The reasoning here is that you cannot hope to truly understand your users if you aren’t one yourself, and, subsequently, you will struggle to create a persuasive technology.

The Entertainer


The Dealer

Those who blatantly exploit.   


Get This Book

Hooked by Nir Eyal
Hooked by Nir Eyal


Hooked: My Conclusion

And that concludes this summary of Hooked by Nir Eyal. I thoroughly enjoyed the book and I think you will too. However, it is larger than it needs to be (as is the case with most books), so don’t feel guilty for skipping certain parts. Finally, take Hooked’s rule of ethics with a large pinch of salt.

The easiest way to get the book in your hands is via Amazon. If you decide to buy the book I’d really appreciate if you did so via the link provided as I get a small commission that makes working on these summaries possible. However, you are under no obligation – feel free to purchase it wherever is easiest! 🙂 

Be well,