Habit formation is a product management topic. In many categories, product-market fit means becoming a habit for your users: something they reach for without deciding to. Retention, the metric everybody chases, is habit formation measured over time. So it pays to understand how habits actually work, both to build things people come back to and to recognize when you are building something people will only ever use once.

The equation

A habit is a recurrent and frequent behavior. A behavior is, basically, an action or the absence of one. The probability of a behavior happening (P) follows this equation:

P = (T * M) / D

Where…

T = trigger

M = motivation (or craving)

D = difficulty

Triggers can be external or internal. For example:

  • External: an email.
  • Internal: being bored.

Difficulty is the sum of six types of cost:

  1. Time cost: how long does it take?
  2. Monetary cost: how much does it cost?
  3. Cognitive cost: how much do I have to think?
  4. Physical cost: how much physical effort does it require?
  5. Social cost: how will others judge me?
  6. Opportunity cost: what am I giving up to do this?

Finally, there are three universal motivators:

  1. Safety: the feeling of stability, security, hope… The lack of fear.
  2. Pleasure: the feeling of joy, satisfaction, happiness, and relaxation.
  3. Social acceptance: being accepted and recognized by others.

Rewards

For a behavior to become a habit, it has to be repeated frequently (as frequently as possible) and it has to yield a reward.

Rewards come in three forms, each tied to one of the motivators:

  1. Social rewards: recognition from the “tribe”.
  2. Resource rewards: money, food, and other things you need to live.
  3. Satisfaction rewards: anything from the feeling of inbox zero to turning your brain “off” in front of Netflix.

Rewards are more powerful when they are variable or random. A variable reward creates a sense of mystery and increases the craving, which in turn increases motivation.

There are also anti-rewards:

  1. Social punishment.
  2. Loss of resources.
  3. Pain (not necessarily physical).

How to drop a habit

  1. Get rid of the trigger, though this is impossible when the trigger is internal.
  2. Make it harder to do: increase all six costs.
  3. Create anti-rewards.

Another option is to replace the habit. Find another behavior and attach it to the same trigger. Ideally, the new behavior’s reward should be better than the old one’s.

How to adopt a habit

  1. Find a trigger that occurs frequently in your life and start the behavior right after it.
  2. Make the action easy to start, and painful to avoid if possible.
  3. Start small. Make the behavior short and easy to finish.
  4. Assign a reward to it.

Back to products

Read those two lists again as a product manager and they should look familiar. Onboarding is difficulty reduction. Notifications are external triggers. The feed is a variable reward. Churn is what happens when the trigger disappears or the reward stops being worth its cost.

Building a product people keep coming back to follows the same equation.