Book review: Hooked: How to Build Habit-Forming Products

Why can’t you create an exciting product?

You may want costumers to use your products if you are an engineer or a designer. However, it is not easy, and it is very tough to think out an innovative approach. The highest wall in front of you is that you are busy keeping up with latest technology, such as new programming languages, growing AI, or evolving gadgets.

Here is one solution for such situation.

Hooked: How to Build Habit-Forming Products

This book is written by Nir Eyal, who have taught at Stanford graduate school of business and design. He proposed a simple model that shows a guidance to an attractive product by which users are “HOOKED”.

The overview of the model is as follows:

The Hook Model

The hook model consists four parts: Trigger, Action, Variable Rewards, Investment. These parts are cycled; users are triggered at first to act, then they get rewards, and invest to be triggered.

Slide number 109 is an example of Pinterest.


I feel this part is the easiest of four parts. You would notice many application related to Trigger you have already known after answering following questions.

  1. When do you feel hungry in walking around the city?
  2. Why do you look back at beautiful ladies?
  3. Why do you flick your smartphone while you are at work?

This part is popular, and Japanese researcher proposed “Shikakeology”, derived from “Shikake”, which means tips to make people behave in a specific way without informing them of the true purpose.

This is a bit ridiculous example of “Shikakeology”, which makes you close a curtain, instantly made by me…


Action literally means some behaviors taken for some reasons. In the example of “Shikake” of the curtain, closing the curtain is a kind of Action.

Why do people act? The answer is in the next part.

Variable rewards

This part is the most important part to make customers hooked. There are two types of rewards globally; intrinsic and extrinsic.

This idea, intrinsic and extrinsic, is deeply investigated by Deci and Ryan, who are researchers of motivation theory, Self-determination theory.

If you close the curtain, sorry for persisting in my ridiculous art, because you want to show your love, it is intrinsic motivation, which is recommended for habits making. On the contrary, presume that you can get money by closing the curtain, you won’t continue to do it after the reward stops. This motivation degradation is referred to as “undermining effects” in psychology.

Like on Facebook is a good example of intrinsic motivation. People feel satisfied if they get many Likes, and they become motivated to post a new picture.

For the better products, it is necessary to understand the difference between intrinsic and extrinsic motivation.


The last part is where the customer works. This part is necessary to continue the hook cycle.

What is important is that a customer him/herself act to make the service more valuable. Good products are always accompanied by diligent customers.

On Facebook, people look for new friends to connect, and new community to join. They sometimes create new community groups with some friends on Facebook. It is laborious, but important for them to improve the system. It is a kind of investment here. In the curtain closing, …. I want to stop here.

Today, I introduced useful tips for value creation in your products. I started working at an automobile company, and work on future human-machine interface, such as healthcare, or entertainment.

Although this is just a simple review for value creation, I will be very happy if you find this interesting and useful in your works.

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