In the November 2002 issue of the HFI newsletter, Bob Bailey discussed the research on optimal line length when reading text on a monitor. He concluded that users read faster if the line lengths are longer (up to 10 inches), but users tend to prefer lines that are moderately long (4 to 5 inches). Some of the research he cites is recent, but some predates computers. I suggest that the research results are not so clear cut.
This issue of the newsletter takes a close look at two recent research studies. Dr. Bailey referenced one study by Bernard, Fernandez, and Hull. I'd like to take a closer look at that study here, and review even more recent results that just came out in 2003.
In the Bernard, Fernandez, and Hull study from 2002, the researchers used both adults (ages 18 to 61, median of 29) and children (ages 9 to 12). They used 3 different line lengths:
They found no significant differences on reading time for either children or adults when comparing the different lengths.
But when they asked a series of preference questions they got some interesting and statistically significant results. The adults said it was easier to concentrate on the narrow length than both the medium and full length (statistically significant at p<.01). The children did not have any significant difference on perceived concentration.
Both children and adults had definite preferences. No adults chose the full length as their favorite. Most chose medium length, and narrow length was not far behind. For the children the full length was also the least preferred, with a strong preference for the narrow length.
The researchers were also interested in the relationship between scrolling and line length. They asked the adults which condition had the optimal amount of scrolling, and there was a significant difference there – the full length condition was perceived as more optimal for scrolling than the medium or short line lengths.
So adults prefer a medium line length, children a narrow length, even though this preference doesn't translate into faster reading. But what about the scrolling? Is vertical scrolling for reading really bad? Should we use longer line lengths because it has less scrolling? Is people's preference for less scrolling more important than their preference for medium or narrow line lengths?
Another study by Ryan Baker adds more interesting results to ponder. Baker set up three online reading conditions:
Results of the study showed that users took significantly longer to read a passage in the paging condition than in the other conditions. The areas that showed no significant differences are telling as well. There were no significant differences in any of the following: perception that a particular condition was more well-suited for reading, that one condition made information easier to find, or that a particular layout was better for comprehension.
What should we conclude from previous research and these two newer studies? Are we ready to make definite statements about paging vs. scrolling and line length for online text? I don't think so. Although research on line length dates back to previous centuries, research on online reading and paging vs. scrolling is still pretty new. It will take a larger body of research before we can state these guidelines with research certainty. In the meantime, I suggest that so far the results tell us to use a medium line length for adults and a narrower line length for children. Don't be afraid of vertical scrolling, in fact it is better to put more text on a page and have users scroll than to break text up into a lot of pages with no scrolling. Balance is always preferred, though, rather than very long and lots of scrolling or very short and lots of paging. And, be ready to make changes as we learn more.
Bernard, M., Fernandez, M. and Hull, S., (2002), The effects of line length on children and adults' online reading performance, Usability News, 4.2. Baker, J.R., (2003), The Impact of paging vs. scrolling on reading online text passages, Usability News, 5.1.
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