USER INTERFACE DESIGN UPDATE - November, 2002

Insights from Human Factors International, Inc. (HFI)
Providing consulting and training in software ergonomics.
(http://www.humanfactors.com/)


Every month HFI reviews the most useful developments in
UI research from major conferences and publications.
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In this issue:


Dr. Bob Bailey -- What is the optimal line length when reading
prose text from a monitor?


The Ergonomic Pragmatist, Dr. Eric Schaffer, gives practical advice.
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Bob Bailey, Ph.D., Chief Scientist for HFI


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 were only 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).


Note: the references for these studies are posted on the HFI Web
site at http://www.humanfactors.com/downloads/nov02.asp
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The Ergonomic Pragmatist
Eric Schaffer, Ph.D., CPE, Founder and CEO of HFI


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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3-day Annual User Interface Update Seminar presented by
Dr. Robert Bailey.
http://www.humanfactors.com/training/annualupdate.asp.
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REGISTER for Bob's UI Update Seminar:


The schedule for 2003 seminars can be downloaded at
http://www.humanfactors.com/downloads/2003calendar.pdf
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Suggestions, comments, questions?
HFI editors at mailto:hfi@humanfactors.com.


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