CommonLounge Archive

BJ Fogg's Behavior Model: Why do certain behaviors happen?

October 05, 2017

As UX Designers, we are constantly trying to introduce new behaviors into our users’ lives — the Fogg Behavior Model shows that three elements must converge at the same moment for a behavior to occur: Motivation, Ability, and Trigger. When a behavior does not occur, at least one of those three elements is missing. As you can see below, motivation and ability can be traded for each other to some extent:

The model further goes on to break down each of the three elements into sub-elements to make it easier to reason about them:

Core Motivators (Motivation)

  • Sensation: people prefer pleasure over pain
  • Anticipation: people hope for certain things, and fear others
  • Belonging: people yearn for social acceptance, and fear rejection

Simplicity Factors (Ability)

  • time: the lesser time something takes, the more likely it is to get done
  • money: the lesser something costs, the more likely it is to get bought
  • physical effort: the lesser work you have to do, the more likely you are to go through it.
  • brain cycles: the lesser you have to think, the more likely you’ll perform the task.
  • social deviance: the less deviant from the social norms a behavior is, the more willing we are to go through it.
  • non-routine: the more something sticks to our routine, the easier it is to get done.


The third element of the Fogg Behavior Model is Triggers. Without a Trigger, the target behavior will not happen. Sometimes a Trigger can be external, like an alarm sounding. Other times, the Trigger can come from our daily routine: Walking through the kitchen may trigger us to open the fridge. Examples of triggers in web products include push notifications, emails, etc. for external triggers, and an inherent desire to do something as an internal trigger (say when I’m about to eat fancy food, I want to instagram it!)

The model is a simple way to think about behavior design, and when you’re thinking about why your users are not doing what you want to do, it helps to think using this as a reference model: is it because they lack a motivation? Is it because the task is too complicated? Or is it because they’re just missing the trigger to remind themselves to go through the task.

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