Understanding user interface design rules - Part 2: System vocabulary and risk

People want to focus their cognitive resources on their own goals and tasks, not on the software they are using. They just want to accomplish their goal, whatever it is. They are not interested in the software. They interpret what the system presents only superficially and very literally. Their limited attentional resources are so focused on their goal that if they are looking for a Search function but it is labeled "Query" on the current screen or page, they may miss it. Therefore, the terminology in an interactive system should be designed for maximum consistency.

The terminology used in an interactive system is consistent when each concept has one and only one name. Caroline Jarrett, an authority on user interface and forms design, provides this rule:

This means that terms and concepts should map strictly 1:1. Never use different terms for the same concept, or the same term for different concepts. Even terms that are ambiguous in the real world should mean only one thing in the system. Otherwise, the system will be harder to learn and remember.

An example of different terms for the same concepts is provided by Earthlink's frequently asked questions (FAQ) page in the Web-hosting section of its site (see Fig. 11.10). In the question, the two available Web-hosting platforms are called "Windows-based" and "UNIX-based," but in the table they are referred to as "Standard" and "ASP." Customers have to stop and try to figure out which one is which. Do you know?

An example from Adobe Photoshop shows that inconsistent terminology can impede learning. Photoshop has two functions for replacing a target color in an image: Replace Color, which replaces the target color throughout an image with a new color, and PaintBucket, which replaces the target color in an enclosed area with a new color. Both functions have a parameter that specifies how similar a color in the image must be to the target color before it will be replaced. The inconsistency is that the Replace Color function calls this parameter "Fuzziness," but the Paint Bucket function calls it "Tolerance" (see Fig. 11.11).

FIGURE 11.11 Photoshop uses different names for the tolerance parameter in two color-replacement functions: (A) "Fuzziness" in Replace Color; (B) "Tolerance" in Paint Bucket.

Photoshop's online Help documentation for Replace Color even says "Adjust the tolerance of the mask by dragging the Fuzziness slider or entering a value" [emphasis added]. If the parameter were simply called "Tolerance" in both color replacement functions, people who learned one function could quickly transfer that learning to the other. But it isn't, so people have to learn the two functions separately.