Principles of Good Interface and Screen Design 175

Step 3: Principles of Good Interface and Screen Design 175

The research on textual material is clear. One of the earliest studies, Tinker (1955), in

a study of reading from hard-copy materials, found that mixed-case text is read signif- icantly faster than uppercase text. Subsequent studies also found large advantages in reading speed and reading comprehension for mixed-case text. The advantage of mixed-case over uppercase text is that it gives a word a more distinctive shape. Uppercase letters are all the same height while lowercase letters have different heights. These height differences aid comprehension.

The research on screen captions and menu choice descriptions, however, leans in another direction. Studies have found that captions and menu choice descriptions using uppercase characters are searched faster than those using mixed-case characters.

Why this difference? The materials giving better results for mixed-case text appear to be of a longer, textual nature. The caption materials appear to be single words or short phrases. It may be that the superiority of mixed-case text does not exhibit itself until text of an extended nature is read. Why short uppercase captions were actually superior to mixed-case ones is unknown. In light of this research, the following is rec- ommended.

Mixed case. Always use mixed case for anything textual in nature, including text

itself, messages, instructional information, figure and table descriptions, and so forth. Text, messages, and instructions reflect the years of research on readability. Also use mixed case for most other screen components, including control cap- tions, data, control choice descriptions, and menu descriptions. These mixed-case recommendations also reflect what is becoming a de facto standard, found in var- ious product style guides. One choice in using mixed case is whether to use the sentence style or headline style of presentation. Sentence style is what you are read- ing now: the initial sentence letter is capitalized and the remainder of the sen- tence is lowercase (except for acronyms, abbreviations, proper nouns, and so on). Headline style involves capitalization of all significant words in a sentence. For anything more than one sentence in length, the sentence style must be followed in presenting textual information. For short phrases, such as control captions and headings, the more declarative headline style may be used.

Uppercase. Unfortunately, many style guides recommend presenting everything on

a screen in mixed case. That this is an extrapolation of the textual reading research to all written words can only be assumed. Contrary to style guide rec- ommendations, on screens capitalization can and should be judiciously used. Consider using uppercase text for the screen title and, most importantly, for all screen headings. Capitalization will set headings off from the many other screen components described above, which are displayed in mixed case. Headings on screens are a learning aid. They enable the user to become familiar with screen organization and relationships. With experience, the screen user finds headings less important. Capitalization will set them off from the remaining screen ele- ments, making them easier to ignore when they are no longer needed. Screen design research does not discount using uppercase. On Web screens, the endless variety of display techniques (different fonts, sizes, weights, and so on) makes the use of capitalization for component differentiation much less necessary. On all screens, however, do consider using capitalization to call attention to impor-

176 Part 2: The User Interface Design Process

substituted for mixed case when a small font size is necessary within a screen component, and the small size degrades word legibility.

All lowercase. In an attempt to be different, text or sentences in all lowercase have begun to appear; that is, there is no initial capital letter on the first sentence word. Be cautious in using this approach; it does not conform to the mental model con- cerning sentence structure we have well-ingrained within us. The visual begin- ning of a sentence anchor point has disappeared, it looks out of context, and it looks very casual. This style is rarely appropriate for a business application.