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News, How-tos, and assorted Views on Accordance Bible Software.

Friday, July 20, 2007  

An Essay on Ease of Use

On Wednesday, I promised to dust off an old e-mail I wrote on the different things that contribute to our perception of a program as easy to use. As I've begun editing and expanding it, it's beginning to turn into an essay! I'm not sure how much this will help you to get more out of Accordance, except perhaps that the next time you hear someone say Accordance is "hard to use," you'll be better equipped to show them the light! Anyway, here is the first installment.

Ease of use is determined by a number of different factors, including: (1) intuitiveness, (2) ease of operation, (3) design (4) consistency, and (5) familiarity. While we can talk about each of these elements separately, they are really intimately interconnected. To help us think about how they are interconnected, consider the following diagram of a see-saw.

I have placed "intuitiveness" and "ease of operation" on opposite ends of the see-saw because they are often in direct tension with each other. Design, consistency, and familiarity combine to form the base of the see-saw. The interplay of those three elements determines how intuitive and easy the user perceives a program to be.

The challenge for the developer is to try and fit all these elements together in a way that will make things easy for users with various levels of skill, experience, and interest. It ends up being a delicate balancing act—hence the image of a see-saw.

Let's begin by defining our terms, then we'll examine each one in more detail.

(1) Intuitiveness refers to how readily someone can figure out how to use a piece of software.

(2) Ease of operation refers to a program's convenience and flexibility, to how easy it is to get things done on a day-to-day basis.

(3) Design refers to how the interface is laid out and how the program operates.

(4) Consistency is technically an element of a program's design, but it is such an important element that it is worth considering separately. If a program behaves in predictable and consistent ways, particularly across the full breadth of its feature set, the user can learn to use additional features more easily.

(5) Familiarity is the one thing a developer has absolutely no control over. If a given user is already familiar with at least some aspects of a program's interface, he will find it easier to use than a program which is unlike anything he has ever seen before. In fact, the more familiar he is with a certain way of doing things, the more likely he is to perceive something different to be "hard."

To understand the tension between intuitiveness and ease of operation, consider the classic interface debate about mouse buttons. Few people who complain about Apple's one-button mouse realize that Apple actually experimented with, and rejected, three and two button mice before they ever released the first Macintosh computer (or its predecessor, the Lisa). The reason they rejected extra mouse buttons was that they were not intuitive. No one (besides a few computer scientists at Xerox) had ever used a mouse before, but they had all been pointing with their index fingers at objects they wanted since they were babies. One button mice took a hand position people were familiar with and applied it to the manipulation of objects in a graphical user interface. Nobody was used to pointing with two fingers and picking up an object with the other three.

People can, of course, be trained to do things which are not immediately intuitive, and that's exactly what happened when Microsoft opted for a two-button mouse. The thing Microsoft did right with the two-button mouse was to give it a consistent function, the invocation of a contextual menu. Thus, while the new user would often make mistakes and click the wrong button, he was being trained with each mistake to access more options with the right mouse button. Once learned, the second mouse button provided a convenience—that is, it provided greater ease of operation.

Thus, Apple chose to produce a mouse which was intuitive, while Microsoft chose a mouse which offered greater flexibility and convenience. The widespread adoption of Windows led to most computer users being trained to use a two-button mouse. Ironically, those who switched to Macs from Windows found the more intuitive one-button mouse to be "harder to use"!

This example shows how creating an interface which is easy to use can be a moving target, or to stick with our see-saw metaphor, a delicate balance. In the next post, we'll look more closely at what goes into making an interface intuitive.

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