Notes on Behaviour Design

Recently I got a chance to see a very interesting lecture by Dr. BJ Fogg on Behavior Design. He is Director at Persuasive Tech Lab, Stanford and runs On the other hand I have also been following Nir Eyal’s blog and his concept of Desire Engine. Here I am trying to do something I usually not do – that is, write down some notes and try to compare these two different models. All credits for this post goes to them, all mistakes are mine. It would be even more interesting to try bringing in perspective of “The Power of Habit” by Charles Duhigg – a book I am currently reading in these notes. Maybe Later.

My interest in behavior design comes from designing new products. Whether we are designing a web application or a mobile application or a physical product, we aspire to change the user behavior in some manner. And above all, we want to inculcate habit in users to use our product. And heres where behavior hacking starts [Hacking has been the buzzword lately from program hacking to growth hacking to now behavior hacking].

Behavior Design 

1. Types of Behavior changes

There are 15 ways behaviour can change. Here is the grid that Dr. BJ Fogg puts down to simplify the behavior design

The Behavior Grid
The Behavior Grid

Now for each type of behavior change, we need a different strategy. And according to him, a strategy befitting one type of behavior change might be completely different from the other. If he is right that this grid makes our life a lot easier by focussing on one type of behavior change or set of behavior changes for designing products. Another interesting point is that sometimes, one may want to move to a particular behavior change with a two-step process (eg. first going for Span Behavior to Path Behavior)

2. Motivation, Ability and Trigger

Behavior change is initiated by a Trigger and there are two things that determine whether user pulls the trigger – Motivation and Ability. Let me come up with a simple example – Lets say a user is looking to buy a smartphone (motivation) and somehow lands up on the relevant webpage (ability), she presses the call to action button (trigger). As a product designer, one’s job is to maximize the motivation to use the product, make it extremely easy to use the product and design an appropriate trigger. Dr. Fogg puts this in a very nice model as shown below (from his website) –

The behavior model
The behavior model

The point he is trying to make is very understandable – For behavior change to occur, one has to be above the Activation Threshold. A good user experience design can make up for low motivation and that is why user experience design is one the most important thing in product design. On the other hand, if motivation is too high and even when behavior change is hard to do, a trigger can lead to behavior change [to use the product]. An anti-UX guy can think that one can always build products that have high motivation value without an easy way to use them. Here comes the third point.

3. Motivation Curve

Practically speaking, our users and human beings and their motivation does not stay the same forever. For instance, a student who is preparing for an exam goes through ups and downs with his motivation levels to get good marks. So if your product is hard to use, the trigger might not always work. And this might hamper the habit formation – the most important thing we want with our products. The motivation curve can vary across people and the behavior change solicited. The point is that with Hard to use product or bad user experience design, one can risk product adoption in lean periods of motivation. And it is difficult to change habits if user goes on and off with the product.

4. Tiny Habits

Dr. BJ Fogg further suggests a way to make behavior change “Easy to do”. This is what he terms Tiny Habits. In his words – “I created a new way to tap the power of context and baby steps. Over 6,300 people have since joined in. The results are the best I’ve ever seen in any program.”

My understanding of this is that desired behavior change can be broken down into mini behavior changes with set of contexts around that can nudge one towards these mini behavior changes. From product design perspective, we can apply it in many different ways. One way clearly I can see is that instead of shoving off a full blown product on the face of the user that require GreenPath change [Do new behavior from now on], we start with simpler things that require smaller behavior changes.

The Desire Engine

Nir Eyal’s Desire Engine is different to some degree. His examples relate more with web products. These two figures (from his website) describe his model.

Desire Engine Path
Desire Engine Path
Desire Engine Steps
Desire Engine Steps







1. Trigger

It starts with a trigger. External or internal trigger. Habits are created when internal triggers become part of routine. And internal triggers are formed with frequent external triggers.

2. Action

Trigger initiates action and it depends on two things whether action succeeds – motivation and ability.

I think these two points are same as the behavior model of Dr. Fogg.

3. Variable Reward

Nir Eyal’s point is that a feedback loop with predictable response does not create desire. The expectation of a reward to certain action create a dopamine surge but if there is variability in reward, the effect is much more.

4. Commitment

Once user is in the action, some kind of commitment improves the experience of the user in the next usage cycle. Although he does not mention it, I interpret it similar to what Robert Cialdini talks in his 6 principles of Persuasion – “If people commit, orally or in writing, to an idea or goal, they are more likely to honor that commitment because of establishing that idea or goal as being congruent with their self-image.” Commitment can be in any form – talking or endorsing the product or paying for it.

The Two Models

I think both the models start with the same three elements – Trigger-Motivation-Ability – that initiates the product usage or behavior change.

However, the two models diverge after that while dealing with enforcement of habit formation. While Nir Eyal talks about variable reward and commitment as two important steps to complete the desire cycle. This desire cycle is then frequently presented to users with improved experience and thus creating an internal trigger and hence habits. On the other hand, Dr. Fogg suggests tiny habits with the power of context to lead to bigger behavior change.

I would love to discuss any other such scientific models we can use to design user behavior.

2 thoughts on “Notes on Behaviour Design

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