Are scrollbars located close enough to where users typically work with a Website or list box to encourage the fastest possible use?
Studies at the National Cancer Institute (NCI) have shown that many users preferred to have the Website content index located in the right panel because it was closer to the traditional right-placed scrollbar (Bailey, Koyani and Nall, 2000). Kangas (2001) reported that about 51% of the most popular Websites are located flush against the left margin of the browser, with the index on the left site as well. The remaining sites are centered on the page. None were found with the Website aligned to the right margin of the browser. Obviously, the scrollbar remains in its traditional location near the right margin.
Erik Kellener, Michael Barnes and Robert Lingard at California State University in Northridge, California recently reported a study that provides some insights into this issue.
They noted that in most list boxes the alphanumeric information tended to be left-justified, while the scroll bar was always placed on the right side of the box. Like with the Websites, the text was on the left, and the scrollbar was on the right. Advocates of the scrollbar remaining on the right side argued that these controls have been on the right side "from the beginning." This was most likely done, they say, to accommodate a "right-handed" user population. The few advocates of placing the scrollbar on the left side, justified their opinions by observing that the scrollbar should be as close as possible to the left-justified text. It is very interesting that they could find no research studies on this topic.
They conducted a study where they had a group of right-handed subjects make numerous selections from list boxes. Users had to scroll to the correct answer and then make the selection. Half of the items (text) were left-justified and the other half (numbers) were right-justified. Half the scrollbars were placed on the traditional right side, the other half on the left side of the list boxes. They found that subjects were reliably faster with, and preferred, similar item justification and scrollbar orientation – that is, right justification with scrollbars on the right, and left justification with scrollbars on the left. There was no appreciable difference between right and left.
They conducted a second study, with different participants to try to replicate the first study, using only text items (e.g., the names of states, provinces and territories). Again, they found that similar item justification and scroll bar orientation produced reliably faster selection times.
It is not surprising that users will perform better with scrollbars that are located as close to the items being selected as possible. This is probably true for all vertical scrollbars, both in list boxes and in the Website itself. As designers our choice is simple, we can either move the most frequently used information to be near the scrollbar, or move the scrollbar to be closer to the information. Roller buttons on the mouse have helped to alleviate, but not eliminate, this problem.
Bailey, R.W., Koyani, S.J. and Nall, J. (2000), Usability testing of several health information Websites, National Cancer Institute Technical Report, September.
Kangas, S. (2001), Layout and content of popular sites
Kellener, E., Barnes, G.M. and Lingard, R. (2001), Effects of scroll bar orientation and item justification, Proceedings of the Human Factors and Ergonomics Society 45th Annual Meeting
Anyone who thinks vertical scrollbars have always been on the right isn't competent to be making claims like that. The vertical scrollbar was (and still is) on the left for the X11 terminal emulator "xterm" (and the text editor Emacs).
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