We like to think that we behave in a logical manner, justifying our decisions based on concrete rationale, demonstrating precisely how and why we have come to our conclusions.

But how many of our decisions are actually truly rational?

When making purchase-related decisions it’s believed that we are rational for only about 20% of our time – the other 80% of our decision-making is led by our emotions.

When thinking analytically about UX tasks, we can often fall into the trap of projecting our perceived rationalism onto the users we are designing for. Despite having empathised with our users through personas and target audience definition – we end up only empathising during their rational states.

When researching the decision-making process, people are now thought of as being in one of two states: System 1 thinking, or System 2 thinking.

System 1 is our intuitive, impulsive, autonomous way of making decisions. We don’t feel like we are thinking or working our brain intensively, as we effortlessly make fast ‘skilled’ choices using our previous experiences. We often call this ‘gut feeling’.


This system lends itself to automating behaviours so we can focus on other things, facilitating creativity by allowing us to be more open minded, and relaxing conventional constraints. It does however make us act more on impulse, only responding and planning for the immediate future, unable to comprehend the cause and effect of our actions, and resulting in overly optimistic and slightly naive beliefs.

System 2 is our controlled, deductive and rational way of making choices. We are often very conscious about what we are doing, which means we require a great deal of effort to reach controlled results through an analytical process. We refer to this as ‘using your brain’.


This system allows us to think in abstract ways to perform complicated calculations and work in realistic terms, predicting outcomes. It makes us feel good about ourselves, giving ‘proof’ of successful reasoning. The downside is that we are unable to sustain this for long periods of time, and it can often lead us to be dismissive towards ideas or new concepts.

In the field of UX and design, rational descriptions of why a solution supports the user are often required to score and justify concepts. But this is based on the assumption that users make rational choices, despite psychologists and anthropologists showing us otherwise.

The majority of the effort put into performing and justifying UX work often only addresses the 20% of decision-making where users are thinking rationally. The remaining 80% is strongly connected with branding.


But there are a few UX-based tactics to consider for these more emotional and ‘instinctive’ user behaviours.

UX approaches to designing for irrationality:

• Identify the key decision making aspects and consider how they may be biased by emotional or intrinsically motivated factors.
• Record peripheral elements, which may influence how key decision-making factors are perceived.
• Map the touchpoints on the user journey and note where the users may be affected by psychological priming prior to a decision.
• Assess how previous experiences may make the users blind to certain parts of the user journey.
• Perform user tests for the critical stages of the design hypothesis.

Rational choice and reasoning is still a very important part of user behaviour, especially as a justification of emotions. However, if all user decisions were rational, our client’s success would simply rely upon their products being objectively superior to all competition.

We should embrace our innate human imperfectness in relation to decision-making, giving clients an edge over tough competition by supporting user experiences that may be shaped by unpredictable and irrational tendencies.

For more information about the topic or general UX banter you can get in touch with the team at ux@welovedigital.com or like us on Facebook to stay up-to-date.

Further reading:

Thinking fast and slow – Daniel Kahneman
Predictably irrational – Dan Ariely
How we decide – Jonah Lehrer
Nudge – Thaler & Sunstein

view all blogs >

Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now