What is Usability?

Somebody called me a usability expert the other day.  Usability expert, I repeated to myself, smiling  — ohhh, I liked the sound of that.  Yes, I’m completing a masters in human computer interaction, this is true.  Yes, I love to think about usability and am constantly considering the usability of everything I interact with.  Yes, you will find books related to various aspects of usability and human-centered design on my bookshelf.

So, you can understand how quickly my satisfaction turned to emotional catastrophe when I found myself deer-eyed when confronted with the question, “So, what exactly is usability?”  I floundered for a few minutes, then said some nonsensical sentence filled with fluffy superlatives designed to obfuscate the fact that I hadn’t taken the time to really think about this most obvious question.  So, humbled, I took to the place of knowledge…

A quick Google search for usability returned a wide variety of responses to the seemingly simple question “What is usability?”  The range of responses was really quite incredible.  I couldn’t believe it, but I could not find one unified, reasonable definition of what usability is.  Examining the definitions and abstracting their ideas, I found a few key ideas repeated throughout:

1. Usability relates to how easy it is to use an object to achieve specific goals.

This is the one thing that is central to the definition of usability in almost all cases. One definition includes the stipulation that it must be easy to use without specific training.  That seems reasonable: usability is about how easy it is to use things.

2. Usability is a measure.

The US government defines usability as is the measure of quality of a user’s experience when using a website.  Another definition states that it’s the measure of the potential of a product to accomplish a user’s goals.  Okay, so usability is a measure.

3. Usability is defined by a number of qualities.

Many definitions of usability include lists of qualities that a product must have in order to be deemed usable.  Qualities that are frequently listed include:

  • learnability
  • efficiency
  • error tolerability
  • effectiveness
  • engaging

After reading all of these definitions, I couldn’t help but feeling… disappointed.  To summarize what I’d learned through this exercise, I asked myself “okay, so what is usability?”

“Well, usability is the ability use something easily to accomplish a specific goal (or set of goals) that a user wants to achieve.  There are a number of factors that make something usable including… It relates to the … ugh.  This is all crap.”

Clearly, I wasn’t convinced.  It’s a no-brainer to write sentences like “usability is the art and science of … with respect to… <list a bunch of desirable qualities here>”.  This sounds somewhat professional, and to the non-critical mind, convincing.  But what does it mean?  What makes something easy to use?  What kind of measure is usability?  What are we really measuring?

So, my search continued.

I read further, probing the Internet for answers, searching deeper and deeper only to find more lists of factors that make things usable.  At least almost everybody agrees on that usability has something to do with using something to achieve a goal.  I just kept reading, and I got nowhere.

To make matters worse, as I was typing, my computer stopped registering all of my keystrokes so half of my words appeared misspelled and I had to spend half of my time going back and correcting “my” mistakes (which were not my mistakes at all, but the fault of the system I use to write my blog).  I just coldn’t hlpbut feing lke th definiton o usabiliy ws missing something very imporant, but I cldn’t quite put m fingeron what tht fctor ws…

FRUSTRATION SET IN.  I felt hopeless.  Convinced that nobody knows what usability is, (especially the manufacturers of my keyboard), I went to bed.

— The next day —

This morning, as I recovered from my nightmares of my inability to find or come up with a functional definition of usability, I was performing my usual morning rituals (I’ll spare you the details) which generally includes some good reading.  And there it was!  The definition I was looking for!  In Steve Krug‘s great book on Web Usability, in plain English that just makes sense, he writes:

…usability really just means making sure that something works well: that a person of average (or even below average) ability and experience can use the thing–whether it’s a Web site, a fighter jet, or a revolving door– for its intended purpose without getting hopelessly frustrated.

As I read it, a rush of pleasant tingling sensations swept over my body.  It just felt right.  Beautifully articulated, it encompasses all of my conceptions about usability.  No fancy words, no long lists, just the plain and simple truth.  Now that’s practising what you preach.

But this still leaves some lingering questions:  What makes a site easy to use?  How do you measure a site’s usability?  These are valid questions, and I will be answering them in other posts.

About Jonathan

Following an undergraduate degree in computer science, some worldly adventures, and years in the software industry, I find myself back at school getting a masters degree in Human Computer Interaction. And I love it.
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