There’s a well known rule that we are only able to process 7 plus or minus 2 pieces of information at a time – it’s the magic number 7. We can improve the usability of our products by taking this in to account and reducing the cognitive load for our users.
There are 3 kinds of Cognitive Load:
Intrinsic Cognitive Load
The Intrinsic Cognitive Load is the inherent complexity of the task in hand. Drawing a square is a lot easier than drawing a portrait. There is little we can do about the intrinsic cognitive load, some things are simply harder than others. However, we can manage it by chunking the information in to smaller problems so that each can be dealt with in turn before re-integrating the information back in to the whole.
Extraneous cognitive load
Extraneous Cognitive Load is the result of the way that the interface or information is presented and structured. As designers this is where we have the greatest impact. For any given task, a well designed and clear interface will have a lower extraneous cognitive load than a badly designed one. Obviously, we should not add to the complexity of the underlying problem by producing complicated interfaces!
Intrinsic and Extraneous load are additive – they combine to form the load of the task. A simple problem presented badly can have the same total cognitive load as a complex problem presented well.
Germane Cognitive Load
This is the “good load” and we want to maximise it. It’s the spare capacity to deal with the underlying information (the intrinsic load) – the capacity available to perform the mental work that leads to understanding. If a task has a high intrinsic load but a low extraneous load, then the Germane load will be high as the user is able to focus their available resources on understanding the problem. If the same task has a higher extraneous load then the Germane load decreases because the user is having to expend resources on dealing with the extraneous elements.
How to lower cognitive load
- Minimise the “noise” in your interface by remove unnecessary visual elements. These increase the cognitive load as they need to be processed in order to determine their relevance.
- Chunking – reduce number of things that a user has to worry about at once by breaking the task down in to chunks. For example a “Wizard” style interface can help reduce the amount a user has to focus on at any one time.
- Consider having an “Expert Mode” for the more advanced settings
- Ensure the information relevant to the task in hand is available (so the user doesn’t have to remember it) people are much better at recognising the thing they want than they are at remembering it!
- The time it takes to make a decision increases with the number of choices available (Hicks Law), so try to reduce the number of choices (e.g. by writing opinionated software)