Why do you check your phone 40 times a day even when you have no notifications? Why people get so addicted to social media? The book Hooked: How to build habit forming products give insights about how companies use psychology to keep us engaged, to create products that become a habit (behaviour done with little or no conscious thought).

The hook model, the one that a habit forming product must follow consists of four phases: trigger, action, variable reward and investment.

The trigger is the spark that ignites the user behaviour. The action is the behaviour done in anticipation of a reward. The variable reward is key to generate a craving and I will explain this in more detail later on, and finally the investment that occurs when the users puts something into the product of services such as time, data, effort, social capital or money.

I would like to focus this post in the variable reward, as this is in my opinion, the one that goes deeper into human psychology and behaviour.

The variable reward

Studies reveal that variable rewards, the ones that we get after a random number of tries, increase the frequency users complete the intended action, see B. F. Skinner.

Variable rewards can be found in all sort of products and they fuel our drive to check e-mail, facebook, twitter etc ...

According to the author variable rewards come in three types: the tribe, the hunt and the self.

Rewards of the tribe

These are social rewards, driven by our need to connect with one another. Many of our institutions and industries are built around this need for social recognition and acceptance, like religious group and social clubs.

A clear example using this type of rewards is Facebook provides numerous examples of variable social rewards. The uncertainty of what users will find each time creates intrigue, that is why you feel the urge to check facebook so often. Likes and comments offer tribal validation and provide variable rewards that motivate users to keep posting.

Rewards of the Hunt

Early humans killed animals using a technique known as "persistence hunting".

The dogged determination that keeps the hunters chasing the prey is the same mechanism that keeps us wanting and buying. The need to acquire physical objects, such as food and other supplies that aid our survival, is part of our brain's operating system.

Twitter uses this type of rewards. The Twitter timeline, for example, is filled with a mix of both mundane and relevant content. Sometimes you will find pieces of useful information and some others you won't. To keep hunting for information, you keep scrolling to search for more variable rewards in the form of relevant tweets.

Rewards of the self

There are certain variable rewards we seek for a more personal form of gratification. We are driven to conquer obstacles, even if just for the satisfaction of doing so.

E-mail might be a defining component of the email. For many, the number of unread messages represents a sort of goal to be completed. Applications like Mailbox help users to get that sense of accomplishment helping users to achieve an "inbox zero".


All these techniques have been used for years, and come from years of research and study of the human brain. The book expose them and guide you through examples of products that are currently using the hook model. "With Great Power Comes Great Responsibility" and so it is in our hands to decide whether we use it to motivate and encourage people or to keep them engaged and addicted to a product.