The Usability / Functionality Trade-off

3 min readDec 21, 2018

Imagine you were designing an app that did a thing. And the only UI component of that entire app was a button that said “Do The Thing“. Your users would push it, the thing would happen, and that would be it. The end. It would be effortless. But ease-of-use is only one part of what a usability designer should consider in their designs. Letting your user be in control of how The Thing happens is just as important.

Too much control can be so overwhelming that your users won’t be able to figure out how to do the thing and struggle or give up.

Options, functionality, and features usually sound like a good idea, but can often get in the way of your user’s goals. A potential user may look at long list of options and features and be fooled into thinking that it’s a great product. However, if any functionality isn’t helping your user achieve their goal, then it’s likely in the way of it.

The reason that unnecessary options get in the way is because of the way that our brains store information. Cognitive load refers to the amount of mental effort a person uses during a task. You can think of a cognitive load like a score. Everything that your user has to stop and think about or question has a point value that adds to that score. If that score goes over a certain threshold, they’ll have to put in more mental effort to do the task. (I know that’s not exactly how cognitive load works, but for illustrative purposes, bear with me).

Your system may be intrinsically difficult to use, and that’s OK. For example video games are supposed to be difficult at times. Your application may have your user making tough decisions about their financial future or what to eat for lunch. No matter what, there’s going to be an intrinsic cognitive load. Be sure that the interface and experience that you design isn’t going to add extraneous cognitive load that interferes with their goals. If your user has to stop and think about how a specific option is going to affect what they’re doing, that’s extraneous cognitive load, and it adds up.

With most advanced systems, having fine-grain control of options and settings is paramount in giving your user control they want and need. The difficult part of this is triaging which settings and options to include. You can use a tool like open card sorting where users would create their own pieces of information, in this case which settings they feel are important, and put them in groups. You then translate those results into your UI. Optimal Workshop has a great suite of tools to do just that.

However, be sure to not lose the “Do The Thing” button. This may be helpful for novice users trying to find what to do next. Create your system with the all the fine grain control and edge cases that your advanced users want and need, but define a clear path that tells your users what they should do next (usually in the form of big, green buttons). This way if a novice user gets stuck, they know that they can always click the “Do The Thing” button.

Remember that it’s not always about making your system as easy as possible. Function and control are also just as important.

Photo by Daniele Levis Pelusi on Unsplash

Originally published at on December 21, 2018.




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