Consistency in Design is the Wrong Approach
Current Knowledge is a much better way to think about the problem.
Consistency in design is about making elements uniform—having them look and behave the same way. We often hear designers talk about consistent navigation, consistent page layouts, or consistent control elements. In each case, the designer is looking for a way to leverage the usability by creating uniformity. After all, if the user learns to operate the design in one place, why not have that knowledge transfer to the next. This is all good. But wrong.
For example, let’s look at a design decision our friends at Avis.com once made. At the time, they chose to use the asterisk (*) to denote optional fields instead of denoting mandatory fields. Less than 10% of the fields on the entire site are optional. If they were consistent with the outside world, entire forms would have every field denoted with an asterisk. That might create its own problems.
So, Avis.com’s designers did what designers are supposed to do: they made a choice. They chose to be inconsistent with practically every other form on the web. But they were internally consistent with themselves.
The problem with thinking in terms of consistency is that those thoughts focus purely on the design and the user can get lost. “Is what I’m designing consistent with other things we’ve designed (or others have designed)?” is the wrong question to ask.
Instead, the right question is, “Will the user’s current knowledge help them understand how to use what I’m designing?” Current knowledge is the knowledge the user has when they approach the design. It’s the sum of all their previous experiences with relevant products and designs.
If the designers at Avis had asked, “Will the user know how to separate optional fields from mandatory ones?” they would likely have come to the conclusion that using asterisks to denote optional fields might confuse a user or two. They could’ve used a different typographic or visual solution, or resorted to the old-tried-and-true “(optional)” text next to the appropriate field label.
When you think about consistency, you’re thinking about the product. When you’re thinking about current knowledge, you’re thinking about the user. They are two sides of the same coin. We’ve just noticed that the designers who spend more time thinking about the users are the ones that end up with more usable designs.
Why do we gravitate to consistency? Because it’s easier to think about. You don’t actually have to know anything about your users to talk about making things consistent. You only have to know about your design, which most designers are quite familiar with.
Current knowledge, on the other hand, requires in-depth knowledge of the users. And that takes research time and investigative effort. It doesn’t come cheap, like consistency does. But it produces much, much better results.
Funny thing about thinking about current knowledge: when you’re done, your interface will feel consistent. Why? Because it will match the users’ expectations and, where they expect it to behave like something they’ve encountered before, it does.
(This has the interesting side effect of reinforcing the wrong thing. When you run into a site that feels consistent, you’re not likely to say, “Hey, those designers did a good job because they obviously researched what my current knowledge would be.” Instead, you say, “Hey they made things consistent. We should do that.” Thus, the cycle of poor practice is reinforced…)
My recommendation: anytime someone on your team starts talking about making things consistent, change the conversation to be about what the users’ current knowledge is.
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The original version of this article was published on Sep 15, 2005.