Write Clear Text and Messages 579

Step 8: Write Clear Text and Messages 579

–– Separate paragraphs by at least one blank line. –– Start a fresh topic on a new page. –– Use lists to present facts. –– Emphasize important things by

• Positioning. • Boxes. • Bold typefaces. • Indented margins.

–– Provide a screen design philosophy consistent with other parts of the system.

Prose Text. Present prose text in the standard sentence style, capitalization to start sentences and to indicate proper nouns and acronyms. To attract attention, dis- play an item in all uppercase, bold, or italics. Be conservative in using these tech- niques, however, restricting them to one or two words, or a short phrase. Overuse slows reading speed for extended prose.

Fonts. Fonts chosen for text should be plain and simple and of adequate size for easy reading, either 12 or 14 points. Proportional spacing (width governed by actual letter size, when an “l” is narrower than an “m”) is preferred to nonpro- portional spacing.

Justification. Left-justify blocks of text to give the eye a predictable starting point when moving from one line to the next. Text at the right margin is usually best left unjustified to avoid large gaps that justification can cause between words. Studies also find that non-right-justified (or ragged-right edge) text lines are just as legible as justified text lines. Large spaces left in right-justified text interrupt eye movement and impede reading. The reading speed of right-justified text was actually found to be 8 to 10 percent slower than non-right-justified text in one study. Non-right-justified text has another advantage in that word hyphenation is not required. Experts also say that non-right-justified text creates more visual interest, and is best for very narrow columns of text. Full left- and right-justifica- tion may be considered for long works that require continuous reading and con- centration, such as long text, newspapers, and novels.

Length. The optimum width of a line of text has been the topic of research studies since the late 1800s. The following is a brief summarization of this research. It is derived from an extensive review by Bailey (2002).

The earliest reported studies were by Weber (1881), Javel (1881) and Cohn (1883). The composite of their conclusions was that ideal length was 3.6 to 4 inches in width and their maximum length recommendations did not exceed 6 inches. Tinker and Peterson (1929) found that for 10-point black type on white paper, line lengths between 3 and 3.5 inches yielded the fastest readings and lengths of 7.3 inches yielded the slowest.

The introduction of computer monitors found a reversal in this trend toward shorter line length allowing faster reading. Studies by Duchnicky and Kolers (1983), Dyson and Kipping (1997, 1998), Dyson and Haselgrove (2001), Youngman and Scharff (1998), and Bernard et al., (2002c), most using 12-point

580 Part 2: The User Interface Design Process

Longer line lengths (7.3 to 9.6 inches) yielded faster reading rates than shorter lengths (1.8 to 6.0 inches).

People, however, preferred shorter lengths (3.3 to 5.7 inches) and a three-col- umn format to a wider and faster-reading one-column format.

The conclusion: People read faster with longer line lengths, while short line lengths impede rapid reading. In spite of this, people preferred the shorter line lengths (another example of a preference-performance disparity). So, for fast reading, create line lengths in the 75-100 character range. For user preference and acceptance, use lengths of about 50 characters per line. Avoid very narrow line widths because they fragment the text, making it more difficult to con- struct the meaning.

Line endings. Short lines, if used, are easiest to read and understand if their end- ings coincide with grammatical boundaries or thoughts. Do not break lines at arbitrary points, whenever possible. For example:

Very short lines Very short are easier to read

lines are if line endings occur

Is much better than

harder to at grammatical boundaries.

read if the line endings occur at any arbitrary spot.