UI Design Newsletter – April, 1999

Effects of screen presentation on text reading and revising, Piolat, A., Roussey, J.Y., and Thunin, O., International Journal of Human Computer Studies, 47, 565-589 (1998).

In Dillon's 1992 review of the literature related to reading from computers or from paper, he reported that past research has shown no reliable differences in user performance between reading a full "page at a time" or reading a "line at a time" while scrolling. (Dillon, A., (1992) Reading from paper versus screens: A critical review of the empirical literature, Ergonomics, 35 (10), 1297-1326.)

Do we elicit faster reading performance on the Web when people read a "page at a time," or when they scroll a "line at a time?" Piolat, Roussey and Thunin (1998) attempted to answer this question.

Full-screen paging can be done either using page-up and page-down keys, or by clicking on the on-screen scroll bar to shift the text by a span of lines equal to the screen size. In most systems, changing the entire screen can be much faster than scrolling individual lines.

Scrolling provides only an approximate idea of location (beginning, middle, end) on the screen itself. Scrolling can be slow and tends to disrupt the perception of spatial layout, particularly while the text is moving. This makes it difficult for readers to grasp the overall organization of a text on a screen (i.e., gain a "sense of text"). Having a "sense of text" can be useful to readers, and may help with overall comprehension - the "where" serves to help recall the "what."

Consistent with the results of past studies, these researchers found that reading time did not differ significantly between paging and scrolling. However, the "paging" participants did build better mental representations of the text as a whole, and were better at locating relevant information and remembering the main ideas.

There is a study that does suggest a difference between paging and scrolling for older users. Mead, Spaulding, Sit, Meyer and Walker had young (ages 19 to 36) and older (64 to 81) adults with little computer experience conduct searches using different web sites. The web sites had 19 related pages and were stored on a hard drive.

The participants were tested during 2 two-hour sessions. Nine search tasks were used, and subjects were given 10 minutes to complete each task. The older users had the most problems with tasks that required 3 or more clicks. Also, older users searched less efficiently than younger users (making 81% more moves). Older users were more likely to use a "page at a time," while younger users tended to scroll a "line at a time" while reading.

They found that older users performed best when using full pages of information, rather than long, continuous pages. Most of the difficulties encountered by older users seemed to be directly related to memory limitations. Viewing a "page at a time" seems to require less cognitive load than viewing a "line at a time" while scrolling.

For web sites where older users are involved, we may want to ensure that they are able to view full pages as much as possible, and not always require them to scroll while reading.