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Hooked – or How to make products and influence people "Product people - Product managers, product designers, UX designers, UX researchers, Business analysts, developers, makers & entrepreneurs 30 November 2015 True Book, Growth, Habit, Hooked, Nir Eyal, Product Design, Psychology, Mind the Product Mind the Product Ltd 1181 Hooked by Nir Eyal Product Management 4.724
· 5 minute read

Hooked – or How to make products and influence people

As Head of Product at WorldRemit I’m always looking for new ideas and inspiration. Who better to turn to than a man who has successfully sold two start-ups and lectured at Stanford on business and design? So a few months ago I bought Nir Eyal’s book Hooked.

Hooked promises to teach readers how to build habit-forming products. The underlying model of all habit forming products, Eyal says, has four steps — trigger, action, variable reward and investment. Here’s my take on the model, focussing on the ideas I found most valuable as a product manager and those that were least convincing.

Hooked book

The Hook Model

The first two, trigger and action, are pretty common sense. The trigger is the catalyst that causes a person to use your product and it can be internal or external. For example, an internal trigger to use Facebook could be boredom or loneliness and an external trigger could be a notification saying you’ve been tagged in a photo.

The action is whatever a user does to engage with your product in hope of a reward, e.g. opening your app. The Fogg behaviour model explains that a person takes an action only when all of the following are present:

  1. Sufficient motivation to take the action
  2. Ability to take the action
  3. A trigger to take the action

Focusing on the ‘ability’ part, Eyal discusses something that all good product managers already know: if your product isn’t extremely simple to use, no amount of triggers (e.g. marketing) will make it popular. In the action section, he also gives a brief run through of some persuasive techniques that play on cognitive biases, like the anchoring effect. If you’re interested in these, you can find many more in Kahneman’s Thinking Fast and Slow.

For me, the really interesting part of the book starts when he gets onto the idea of variable reward. The theory is that a variable reward keeps users coming back more often than a fixed reward. This is counter-intuitive from some angles: if you could produce a product that predictably delivered a great reward, it would probably get boring more quickly than a product that sometimes missed the mark. Presumably this explains why gambling is more exciting than receiving your monthly paycheck.

In fact, neurological researchers have found that our brain is stimulated not when a reward is received, but rather in anticipation of receiving a reward. In a study, pigeons who reliably received food as a result of tapping a lever, tapped the lever dramatically less often than pigeons who only received food after a random number of taps. The takeaway here is that you can maintain user interest in your product by sustaining variability.

Eyal outlines 3 different kinds of reward, which he nicknames rewards of the tribe, hunt and self. Rewards of the tribe are social (likes, upvotes), rewards of the hunt are about acquiring cash or information and rewards of the self are about the satisfaction of mastery or completion (completing all stages in an online learning program).

The section on user investment in a product is the most interesting of all. The idea is that a user will keep choosing your product if they’ve put some investment into it, for example gaining followers on Twitter, entering and saving their card details on an ecommerce site or reaching a high episode on Candy Crush Saga. There are also cognitive biases at play because, for example, users have a tendency to overvalue their own work — which is why we all feel so attached to the Ikea furniture we build.

Eyal explains that when a user has just enjoyed their reward, they are primed to reciprocate and put a little more back into the product, even set up their own trigger for the next use. I found this to be the single most useful insight from the book, and I rushed into work the next day thinking of ways we can help users set up their own triggers after they’ve completed a money transfer. The resulting feature, letting users set themselves a reminder to send to the same recipient again on a given day, has been hugely successful at driving reengagement with our product.

I’m with the Peddlers

My major complaint with the book was the ‘Manipulation matrix’ in which Eyal talks about which kinds of products it’s morally right to build. He asks two questions of a product:

  • Does it materially improve the user’s life?
  • Would the maker use it herself?

On this basis, he criticises people who build products that materially improve users’ lives, but do not use their own products, calling them ‘Peddlers’ and reserving praise for people who solve only their own problems.

Hold on. Software engineers, designers and product people are drawn from a tiny cross-section of the population. If they don’t look further afield than their own problems, surely they will only produce a very narrow range of products.

The problems of this approach are nowhere more obvious than in digital health products, which time and again are aimed at already fit, 20- to 30- somethings because the product designers are building for themselves. Consequently they are missing the chance to build for people with serious health conditions who could benefit the most from mobile monitoring and health information tools (great article on this here).

In government, I worked on services for user groups including prisoners and National Health Service nurses, neither of which groups I, or anyone in my team, had ever belonged to. But both definitely deserve to receive the benefits of technology just as much as people who fit the profile of the young, affluent, healthy, white, male people (on average) who design and code products. Sure, you might have to work a bit harder to understand users who are different from you, but that’s what user research is for.


Before you pick up this book, it is worth considering whether you’re even trying to build a habit-forming product. Not all successful products are habit-forming. For example handy.com — a great startup through which I found a cleaner — does not need me to make using its website into a habit.

It also strikes me that the idea of building a habit-forming product through variable reward is particularly relevant if you rely on revenue from advertising, so that you need to keep capturing a user’s attention with content. If your business model is ecommerce, delivering a consistent reward every time is probably a more compelling proposition for your users.

Overall, though, I thought it was a helpful, thought-provoking book with a nice blend of theory and practical advice. I’d recommend it to product managers in any field who are thinking about how they can get their users to keep coming back. You can also watch his talk from MTPCon last year to hear the model described in more detail.

I’d be interested to hear from any readers who’ve put his ideas into practice, or who are looking for ways to build habits in their products.

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