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UI Design Newsletter – November, 2002

In This Issue

Optimal Line Length

Bob Bailey, Ph.D., Chief Scientist for HFI, discusses the optimal line length when reading prose text from a monitor.

The Pragmatic Ergonomist

Dr. Eric Schaffer, Ph.D., CUA, CPE, Founder and CEO of HFI offers practical advice.

Optimal Line Length

What is the optimal line length when reading prose text from a monitor?

Certain aspects of usability have been researched for over 120 years. One active area of investigation has been the influence of line length on the speed of reading prose text. Weber (1881) made the first research-based recommendations when he suggested that an ideal line length was 4 inches (100 millimeters). He stated further that the maximum never should exceed 6 inches (150 mm). The same year Javel (1881) reported that line lengths should be no longer than 3.6 inches (90 mm). Two years later, Cohn (1883) confirmed that 3.6 inches (90 mm) was the best length, and that 4 inches (102 mm) was the longest admissible line length.

These recommendations were for book, magazine and newspaper publishers, and assumed the use of 10-point black characters typeset on white paper. There only were about 2,000 typewriters in use in the early 1880s. Almost 50 years later there was another flurry of activity on this topic.

One of the best studies was done by Tinker and Paterson in 1929. Using 10-point black type on white paper, they found that line lengths between 3 inches and 3.5 inches (75 to 90 mm) yielded the fastest reading performance. Paragraphs with line lengths of 7.3 inches (185 mm) were read slowest. The authors proposed that longer line lengths obviously require greater lateral eye movements, which seemed to make it more likely that users would lose their place within the text.

As computer monitors were used more in these studies, longer line lengths seemed to enable faster reading performance. Duchnicky and Kolers (1983) found that a full screen length of 7.4 inches (187 mm) resulted in 28% faster reading times over a 1/3 screen length of 2.4 inches (62 mm). In fact, both full screen and 2/3 screen line lengths were read reliably faster than the 1/3 screen length.

Dyson and Kipping (1998) also found that reading rates increased as characters per line increased. In their study using 12-point type, the 4-inch line length produced the slowest reading rate and the 7.3 inch line length produced the fastest. However, users preferred the 4-inch (102 mm) line lengths. They also reported that even though a single wide column was read reliably faster than three columns, users preferred the 3-column format.

Youngman and Scharff (1999) used 12-point type and found that with no margins, an 8-inch line length elicited the fastest overall reading speed, when compared with 4 and 6 inch line lengths. Again, users preferred the 4-inch line length.

Bernard, Fernandez and Hull (2002) had participants read 12-point prose text with line lengths of 9.6 inches (245 mm), 5.7 inches (145 mm) and 3.3 inches (85 mm). They found no reliable differences in the average reading speed for the differing line lengths. Their adult subjects preferred the two shorter line lengths.

The research also suggests that line lengths (columns) can be too short. Dyson and Kipping (1998) found that a line length of 5.5 inches (140 mm) was read reliably faster than a narrower 1.8 inch (46 mm) line length. A more recent study by Dyson and Haselgrove (2001) reported that a 4-inch line length resulted in faster reading than the shorter line length of 1.7 inches

What can we conclude when users are reading prose text from monitors? Users tend to read faster if the line lengths are longer (up to 10 inches). If the line lengths are too short (2.5 inches or less) it may impede rapid reading. Finally, users tend to prefer lines that are moderately long (4 to 5 inches).

References

Bernard, M., Fernandez, M. and Hull, S. (2002), The effects of line length on children and adults' online reading performance, Usability News, 4.2. [This article had a line length of 9 inches on the screen (1024x768 pixel resolution) and 6.2 inches when printed]

Cohn, H. (1883), Die Hygiene des Auges in den Schulen, Leipzig. [See Tinker and Paterson, 1929]

Duchnicky, J.L. and Kolers, P.A. (1983). Readability of text scrolled on visual display terminals as a function of window size, Human Factors, 25, 683-692.

Dyson, M.C. and Haselgrove, M. (2001), The influence of reading speed and line length on the effectiveness of reading from a screen, International Journal of Human-Computer Studies, 54, 585-612.

Dyson, M.C. and Kipping, G.J. (1998), The effects of line length and method of movement on patterns of reading from screen, Visible Language, 32, 150-181.

Dyson, M.C. and Kipping, G.J. (1997), The legibility of screen formats: Are three columns better than one? Computers & Graphics, December, 21(6), 703-712

Javel, E. (1881), L'evolution de la typographic consideree dans ses rapports avec l'hygience de la vue, Revue Scientifique, 1, 802-813. [See Tinker and Paterson, 1929]

Tinker, M.A. and Paterson, D.G. (1929), Studies of typographical factors influencing speed of reading: Length of line, The Journal of Applied Psychology, 13(3), 205-219. [This journal article had a line length of 3.8 inches (97 mm)]

Weber, A. (1881), Ueber die Augenuntersuchungen in den hoheren schulen zu Darmstadt, Abtheilung fur Gesunheitspflege, Marz. [See Tinker and Paterson, 1929]

Youngman, M. and Scharff, L. (1998), Text width and margin width influences on readability of GUIs. [This Web page had a line length of 15 inches on the screen (1024x768 pixel resolution) and 7.8 inches when printed]

Very interesting article. I work with an advertising company as a graphic designer. We are always at odds with our clients about how typesetting differs from word processing and the common issue seems to be a lack of knowledge by people trained as "word processors". Schools who teach word processing appear to be stuck about 10 -20 years in the past in terms of understanding "what" type is and how it works. They think that the computer is simply a typewriter attached to a monitor. I look forward to reading more of the studies you provided here.

Don Nich
Sandbox Creative Group

Reader comments on this and other articles.
The Pragmatic Ergonomist, Dr. Eric Schaffer
Eric

We apply usability engineering to meet specific business objectives. This is a perfect example. You might be creating a site for use by your company's sales agents. The main objective is speed. In this case we use wider text (about 100 characters wide). If you are creating a site for the general public to read news the objective is satisfaction. We don't really care how long it takes to read the news. We just want people to enjoy it. In this case we would use a shorter width (about 55 characters wide).




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