My Product Management Toolkit (52): Behavioural Diagnosis

4 min readMay 16, 2022


About 8 years ago, I first learned about behavioural design. I read “Hooked”, a book about building habit forming products by Nir Eyal. In Hooked, Nir writes about ‘triggers’ that drive behaviours and how these triggers are followed by ‘actions’. Nir’s work offers great insights into the field of behavioural science. A behavioural scientist essentially studies human decision-making, aiming to understand why people behave in the way they do.

With these insights into human behaviour and decision-making, you can design ways to help people take up new behaviours or modify existing ones. This is all in the field of behavioural design. Kristen Berman, CEO and Co-Founder of Irrational Labs, a San Francisco based behavioural design agency, introduced the 3B Framework. The 3B Framework explains the three key elements to behaviour change:

  • Behaviour — Identify one key behaviour to focus on and be specific about that behaviour. For example, some sample key behaviours to focus on: “people taking a shower between 4–6pm each day” or “people in the first month of taking up exercise, tend go to the gym for an hour on two weekday mornings”.
  • Barriers — Barriers are the steps a user has to take and the decisions a user has to make in order to achieve a key behaviour. In behavioural design, one of the goals is to reduce barriers. Barriers cause friction for a user trying to carry out their key behaviours. We want to create a path of least resistance for a user. Think, for instance, about a user who wants to go to the gym to exercise. Physically going to the gym is an obvious barrier and deciding about whether to pay for a gym membership can be a barrier too. Irrational Labs has identified some common barrier types which are useful to take into account (see Fig. 1 below).
  • Benefits — Benefits motivate users to complete a specific behaviour. Benefits can be short term — e.g. I’m brushing my teeth so that I can have a clean breadth now — or long term, where I might save money to create a future nest egg.

Fig. 1 — Common Barrier Types — Taken from:

  • Attention Bias — This describes our tendency to focus on certain elements while ignoring others. There are three questions you can ask to determine whether attention bias is a problem from your key behaviour. Do people remember it? (Availability Bias) Do people see it? (Saliency Bias) Do people want to see it? (Information Avoidance)
  • Cognitive Overload — Cognitive overload occurs when we feel overwhelmed by a lot of options or decisions to make. You can use a number of questions to see whether cognitive overload creates a barrier to a key behaviour. Is the best option clear? (Choice Overload) Do people lack time / energy? (Scarcity or Depletion) Do people lack the confidence to make the decision now? (Procrastination or Decision Paralysis)
  • Status Quo — A resistance to change can also form a major barrier to achieving a key behaviour. A change from the status quo is often perceived as a loss. Do people realise what they’re missing out on by hanging onto the status quo? (Opportunity Cost Neglect) Are there any potential losses from moving away from the status quo? (Loss Aversion, Regret Aversion or Sunk Costs) Is it easy for people to switch? (Cognitive Overload or Decision Paralysis)

A behavioural diagnosis is the first step in understanding the behaviour to achieve and identifying the associated barriers and benefits. When conducting a behavioural diagnosis is we map out every single step someone needs to do to get to a key behaviour.

As the above example shows, a behavioural diagnosis is a very detailed analysis of the environment where a decision happens. These are the main steps involved in creating a behavioural diagnosis:

  • Collect data — Gathering data about the problem to explore.
  • Choose key behaviour — Choose a key user behaviour to focus on.
  • Map the steps — Include all the steps someone has to do to successfully complete the key behaviour.

The level of granular detail thus mapped out is the biggest difference between a behavioural diagnosis and a journey map. Also, in a behavioural diagnosis we look at the mental steps someone takes to get to a desired outcome. Once we’ve got this full understanding, we can then identify any biases or points of friction that affect someone’s behaviour. This in turn will help us in coming up with hypotheses about how to solve friction or any problems that someone encounters, and how to best these hypotheses.

Main learning point: To me, the biggest value from frameworks like the 3B framework is that they helps better understand behaviour change. Carrying out a more detailed behavioural analysis identifies the steps — both mental and actual — a person takes to get to a desired outcome.

Related links for further learning:





Product person, author of "My Product Management Toolkit" and “Managing Product = Managing Tension” — see