Behavioural design

Cognitive load

'Cognitive load' is the measure of the amount of mental resources needed to deal with whatever someone's mind is doing at a particular time.

Everything we do adds some cognitive load; more complex or difficult things adds more. This means that using your willpower, or concentrating very hard, or the distractions of multi-tasking all require the same kinds of mental energy. If you use up a great deal of your cognitive resources on multi-tasking, you'll be less able to resist having a second helping of pudding at dinner.

This has ramifications for the design of products and services. Despite all talk of 'engagement' and 'the attention economy', you (almost always) shouldn't aim for your product or service to take up more of your users' cognitive resources.

There's no better introduction to this than Kathy Sierra's blogpost 'Your app makes me fat'

Estimating cognitive load

Mixing cognitive load estimations into your research and design process can be helpful. It can: 

  • help identify pain points in existing experiences
  • help identify the points in a journey where users are likely to make mistakes
  • give you a cumulative view of user's cognitive load when they arrive at your service
  • act as a checklist for creating a realistic testing environment
  • increase empathy for users

We've made cognitive load cards that can be used to do all of the above.

Download editable Pages version of cognitive load cards

Download PDF version of cognitive load cards

Fill in one card per step in the journey, by scribbling over the options that match that step. The overall amount of colour on the card gives a good at-a-glance view of the cognitive load – see illustration below.

Cognitive load triage

For multistep processes like filling in forms or onboarding onto a service, it's also helpful to do the kind of cognitive load triage suggested by Dan Ariely.

Download triage as a PDF


Kathy Sierra's blogpost 'Your app makes me fat'

Cognitive load triage: download triage as a PDF

Cognitive load cards: editable Pages versionPDF version