The True Measure of Usability

By Deane Barker on May 11, 2006

Lately, I’ve struck upon a new benchmark for usability: the extent to which the interface disappears. Let me explain —

My wife drives a Honda Odyssey minivan. This is the Swiss Army Knife of minivans. It’s set-up perfectly, to the point where I’ve often said, “If you need to find something, close your eyes and use your gut instinct to reach out to where you think it is…and it’s probably right there.” The “interface” of that van disappears. It’s so usable, you don’t even think about it.

I’ve discovered this with two apps with which I’ve been working a lot lately:

  1. GMail
    GMail takes a lot of liberties with how email works, but I don’t even think about the changes. I just expect that a “conversation” will have a list of emails in chronological order. I just expect that a new email should be considered the “reactivating of a conversation.” It just works.

  2. The silverorange Intranet
    This is an old favorite of Gadgetopia, and it’s something we’ve been doing some super-secret work with lately. In the course of this work, I had a long running intranet-based conversation with one of the principals at silverorange. It was during this conversation that I realized that the tool had vanished from my perception, and all that was left in its place was pure communication. There was a point where the tool become such a natural part of how I worked that it just faded into the background.

I remember reading a tutorial a while back about dynamically adding form fields to an HTML form (this was a few years ago — back when this was a really novel thing). The author said that when you do this, your users shouldn’t even notice. Being able to add an extra phone number field dynamically will feel so natural to them, that it won’t even jump out as being a technological achievement.

This, in my mind, has become the true measure of usability, and it’s a combination of a lot of things: interface architecture, visual design, application performance, browser interaction, etc. In a perverse way, the highest compliment someone can pay your app is that they never even noticed it was there.

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Comments

  1. I understand what you’re saying. I know very well the joy of using an intuitive interface (iPod, TiVo). However, I think what you’re describing is that you are just approaching the asymptote of the learning curve for these interfaces. All interfaces have a learning curve, even if they’re so intuitive all you are doing in the first use of the interface is confirming your instictive actions.

    From Wikipedia: “The learning curve effect states that the more times a task has been performed, the less time will be required on each subsequent iteration.”

    As the number of times the task has been performed approaches infinity, the time required to perform the task approaches zero! So, it all depends on where you are on the learning curve. Just the way driving a car becomes second nature, any interface could probably similarly become second nature with enough repetition, right?

  2. Congratulations Deane, you just summed up why many Mac users love using Macs. Things are where you’d expect them to be and things just work. I never thought you’d make my argument for me. Perhaps now you see where Dave and I are coming from.

  3. The two comments above bring up a good point and provide an example. The first commentor says that everything will fade into the background if you use it enough, but some apps are so usable that this “training period” is shorter than others.

    The second comment from Rob the Mac Troll got me thinking about Windows. It too fades into the background when I work — I don’t even think about it. But it’s not a good example because I’ve been using it so long. So does it fade away because it’s well-designed, or because I’ve been working with it for 10 years?

    What this means is that perhaps you can only measure usability in this way on a new app. Apps that you’ve used long enough to get profficient with can’t be measured objectively.

  4. bicyclists have known this for decades. the ultimate complement for a bicycle is that “it disappears underneath me.”

    from smartcycles.com:

    “At times the bicycle disappears underneath me and I ride with the utmost ease, sometimes I get out of the saddle and sprint and look with disbelief that my accurate Cateye computer is showing 35 mph, but overall I get the feeling that this bike is telling me, “Ride me, I will show you how it’s done; ride me.”

  5. As somebody who often finds himself teaching others to use Windows, I can assure you it’s just because you’ve been using it for so long.

    Interestingly, more non-computer users I see can adapt to a Mac relatively quickly. The only problems that occur are when Windows users expect the Mac to work the same.

    Umm… YMMV.

  6. I don’t think even measuring it on a new app will be accurate, because even if the app (or car) is new, how well you are able to make use of its interface will be affected by other user interfaces that you have already mastered, or just used.

    I read a study a while back about how average IQ has risen steadily in the last century (I guess it’s called the Flynn effect), and the study’s authors concluded it’s the user interfaces that bombard our lives that are doing that. It’s not that we’re getting smarter, it’s just that we’re getting more adept at figuring out how to get things done with the gadgets, gizmos & software that we use every day. And as those gadgets become more mainstream, our kids become accustomed to them at earlier ages, and thus become more adept more rapidly at using whatever comes out.

    So I guess it’s not necessarily the interface as much as what we’re expecting the interface to do. If a Rip VanWinkel from 100 years ago were to wake up & find himself in the driver’s seat of your Honda Odyssey, he’d be totally lost.

  7. So does it fade away because it’s well-designed, or because I’ve been working with it for 10 years?

    To some extent, it depends on the situation and severity of poor design. We use an app at work that says “You did not properly shut down the software the last time you used it.” EVERY time you start it up. It does not matter how you shut it down, it always says this.

    No matter how long I use that app, every time see that message it makes me mad. It certainly has not faded into the background with extended use. It annoys me because as a programmer, I know that this sort of this is fixable. However, this may not annoy a non-tech person. It is just another message box to click to log into the system.

  8. I agree wth what Noel says – whoever designed our SQL database here did an extremely poor job with it. It’s buggy and very counterintuitive to work with. I know how to get everything done that I need to do, but if you have to fight the programming every step of the way to do it, it’ll never ‘disappear’.

    But on the other hand, like Noel also said, for someone who doesn’t know that there are better ways to do things, they’d probably have no issues with it. If I had no SQL experience or just little tech experience in general, I’d probably assume that our database represents the status quo of databases and deal with it.

  9. As a user interface designer I’ve come across this many times. In systems philosophy these two states are referred to as “ready at hand” and “present at hand”. The school example for ready at hand is a pencil. Once you’ve grabbed the pencil it no longer exists.

    On the opposite side I would place “setting the digital clock on a vcr”.

    Why can’t I just open the plastic lid to the digital clock and rotate a virtual dail to the right time using my finger?

  10. The problem with the learning curve on Mac’s and PC’s is that the more people use PC’s the less they can use Mac’s, or vice versa. This problem of Mac vs. PC will only get worse as time goes on, because people will become so accustomed to using their PC that when attempting to use the Mac will become frustrating. I don’t really see a way to solve this expect to see what more people use at the end of ten years, then we will see not what OS is best, but what OS more people use.

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