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a blog about the links between ux design and cognitive sciences.

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COGNITIVE BASIS #2 / COGNITIVE LOAD

november 12/ux design, cognitions

If we keep in mind how our users think, we can create designs which support them unnoticeably - for instance if we minimise the amount of mental processing capacity which they have to use.

We have two main types of memory: short-term memory (STM) and long-term memory (LTM). In computer science terms, you might imagine short-term memory as RAM and long-term as the HDD. I will try to describe how they work, how we can design interfaces that eliminate confusion and how to lower the cognitive effort users need to make. All of this should result in a more human-centered user experience.

The human brain is not optimised for the abstract thinking and data memorisation that websites often demand. Many usability guidelines are dictated by cognitive limitations.

Jakob Nielsen Nielsen-Norman Group

The amount of mental processing power needed to use a site affects how easily users find content and complete tasks. When the amount of information coming in exceeds the user’s ability to process it, the overall performance suffers because the cognitive load is too high. That being said, 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.

What is the cognitive load ?

There are three types of cognitive loads:

Intrinsic cognitive load is the energy needed to absorb new information while keeping track of the user’s personal goal.

Extraneous cognitive load is anything taking up mental resources without helping the user to understand the content, for instance colors, fonts or sizes, which don’t convey unique meaning.

Germane cognitive load is the load used to construct and process schemas. This is particularly interesting for areas such as teaching, but it does not really affect UX design.

The part that we can tackle is the extraneous load, which we should minimise as much as possible.

How to minimize cognitive load ?

Provide short-term memory support.

The capacities of working memory are limited. Consequently, the shorter entries are, the more limited errors are. And the shorter the items are, the shorter the reading time is. Finally, the more the actions necessary to reach a goal are complicated, the more the cognitive load increases and consequently the risks of error are higher.

Solutions to support cognitive load

1. Don’t make users memorize many items at once.
The number of elements that present core interaction points would rather be considered around the memory span (more or less 7 items) which is a function of working memory introduced by the psychologist George Miller in 1956. Beyond the visual simplicity, aim for content simplicity. All essential information should be on the same page as the call to action button. Don’t ask the user to go back and forth to retrieve all information needed to make a choice.

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2. Don’t present too many elements for the choice together.
It’s important to care about the concentration ratio. According to Hick’s law, if you present several choices, buttons, options at once, you should be ready that it will take more time and effort for user’s short-term memory to work them over and this can distract them from making the final decision or interaction.

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3. Save memory effort with recognizable patterns and symbols.
Humans are better at recognising things than they are at remembering them. Moreover, recognition requires less processing in the human brain than recalling, so the risk of error or failure is reduced. We can apply this by for instance using pictures, which the user will quickly associate with an action or information.

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4. Know the mental model of your users.
A mental model is the users intuitive knowledge of how something is supposed to work based on experience. Using layouts and models which your users already encountered in the past, you reduce the energy they need when browsing your website.

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Even if theories allow us to understand multiple behaviours, we are far from knowing all the factors involved in cognitive processes. So there is only one last solution: put a user on your website and watch them!

REFERENCES

  • Nothing Interactive: Psychology in web experience - minimising the cognitive load
  • UXplanet: Designing for memory