- Briefly on Usability

Briefly on Usability

Haptic Devices, the Fat-Finger Problem, and Fitts' Law

Along the popularity of portable touch screen devices like iPhone, our fingers have become one of the primary "pointing devices" in navigating the Web. While the computer mouse may offer a higher level of precision, our fingers allow us to directly interact with on-screen graphics instead of having to move around the mouse cursor: the result is a much more immersive experience.

With this emerged another problem, aptly named the "fat-finger problem." Referring to general difficulty of using a touch screen device, we often face this problem when browsing a website or trying to compose a text message on a smaller device. These issues often feature buttons that may be too small or close together, and they present a series of user interface challenges to the designer.

User's level of productivity and satisfaction have been analyzed in many ways, but Fitts' Law serves as one of many foundational models in UI/UX design. Originally established to analyze human movement in the physical world, Fitts' Law can be applied to web design to measure the user's movement (more specifically, time spent moving) across the screen. The law states "the time to acquire a target is a function of the distance to and size of the target," and in short, we must reduce the time the user spends travelling between one button to another and increase the size of individual buttons as necessary.

Usability and Xerox PARC

Usability and usefulness may go hand-in-hand when building a successful product, but some opt to erroneously use the two terms interchangeably when discussing user satisfaction. Usability deals with the "effective, efficiency, and satisfaction with which users can achieve task," while usefulness recognizes whether a product meets specific needs and supports real tasks.

For a product to be recognized as highly usable, it must possess the following qualities:

  • Easy to learn and remember
  • Efficient
  • Visually pleasing and fun to use
  • Quick to recover from errors

As one can imagine, poor usability may be a minor inconvenience, but lack of usefulness is a deal breaker. However, a seminal 1983 short film "When User Hits Machine" and the subsequent article in MIT Technology Review "Field Work in the Tribal Office" offer a convincing counter-argument against absence of "user friendliness."

A segment shows two men struggling to make a document copy with the latest Xerox product, while the top Xerox managers assume that they are "technologically incompetent subjects" and that they must have been recruited "off the loading dock." The revelation soon follows: both men were computer scientists filmed at Xerox’s Palo Alto Research Center (PARC). One was a well-known computational linguist Ron Kaplan. The other was Allen Newell, a founding father of artificial intelligence.

This popular anecdote serves as a story behind the big green button that today's users are familiar with, as well as an advocate for good design.