Cognitive psychology in UX design: Minimising the cognitive load

We always hear that “good design doesn’t get in the way” — what does that mean, exactly?

This article was originally published on nothing.ch, back in 2014. Since I believe it holds information that’s valuable today still, I’m republishing it here, with a few minor updates.


Cognitive load — the user’s processing power

Cognitive psychology is the study of mental processes such as perception, memory or problem solving. Broadly put, cognitive psychology deals with how people think — which is what makes it relevant for us as designers. If we pay attention to such mental processes, we can for instance reduce the amount of mental processing power people need when using our design.

In psychology, cognitive load describes the mental effort that’s required to learn new information. In UX design, we can think of cognitive load as the mental processing power needed to use a product. If the amount of information that needs to be processed exceeds the user’s ability to process it, the overall performance suffers. The cognitive load is too high.

So how do we deal with this? We can’t change the actual processing power of our users. What we can do is get to know people’s limits, and use that to minimise their processing efforts.

We can’t change the actual processing power of our users. What we can do is get to know their limits, and minimise their processing efforts.

Minimising the cognitive load

There are three types of cognitive loads:

  • Intrinsic cognitive load is the inherent difficulty of a task. In UX terms, it’s the energy people need to absorb new information while keeping track of whatever task they are trying to accomplish with your product.
  • Extraneous cognitive load is anything taking up mental resources to deal with problems that are not related to the task as such. For instance, in design, this could be caused by random use of fonts sizes (which is, of course, not the same as purposefully deployed fonts).
  • Germane cognitive load is the load used to construct and process schemas. This is particularly interesting for areas such as teaching, but it’s also more complex to address through design.

The part that we can easily tackle is the extraneous cognitive load. This is the cognitive load that is, basically, the result of bad design. Our goal should be to minimise it as much as possible. What follows are five ways to reduce extraneous cognitive load.

1. Provide short-term memory support

Our short term memory stores information for about 20 to 30 seconds. Miller’s Law argues that the number of objects which a human brain can hold in short-term memory is 7 ± 2. To reduce cognitive load, we can support users by displaying information which they would otherwise have to store in their short-term memory. These are often simple things like making a visited link look different from a non-visited one.

2. Use recognition rather than recall

Humans are better at recognising things than they are at remembering them. Recognition actually also requires less processing in the human brain, so there is less risk of error or failure. Consequently, our design should trigger recognition over recall. We can apply this by for instance employing pictures that users can quickly associate with an action or information.

3. Avoid visual clutter

This one goes almost without saying: Design should be simple. Avoid using five different fonts or meaningless pictures — if you use something, you should be able to explain why. Don’t try to create the “wow” effect, strive for “of course”-design, which convinces by being invisible.

4. Make it simple

Beyond visual simplicity aim for content simplicity, too. All essential information should be on the same page as the call to action button. Don’t ask people to go back and forth to retrieve the information they need to make a choice.

5. Know the mental model of your users

A mental model is a person’s intuitive knowledge of how something is supposed to work based on their own experience. You can support users by employing layouts and models which they’ve already encountered in the past.

Needless to say, these are guidelines, not rules. There might indeed be a context where you do need five different fonts (to be fair, I doubt it, but change my mind!). At the end of the day, it boils down to one simple aspect: you don’t want people to notice your design. Not noticing means not using unnecessary brain power to process it. That’s when design doesn’t get in the way.