Andrew's Usability in the Real World: A Mars Bar among Light Bulbs

I'm fascinated by what people see, and what they don't: what you might call 'the rules of attention'. Understanding these rules is important for those of us who deal with websites and other interactive designs, but before I get to that – and an interesting phenomenon with web design that we've recently observed – I’d like to tell you a story.

I used to live in the United States. In the early 1990s we had new friends who had just emigrated from what was then the Soviet Union. One day we went together to one of those vast warehouse stores, the kind that sell everything in enormous multipacks.

It was a bit overwhelming for me, but for our new friends fresh to this kind of consumer culture it was all but impossible to take in. Standing in front of a 30-foot bank of tinned tomatoes, corn, and green beans, they would ask 'Where are the canned vegetables?' They couldn't see them.

The rules of attention were different for them compared to the average US consumer, and rules of attention can be different for anyone depending on context. But the rules are not entirely arbitrary, and to the extent that they can be understood, they give a designer great power. This is true whether the design is for the layout of a grocery store or the template of a web page.

The 'rules of attention' can be based on unique idiosyncratic circumstances, as with our friends who moved to America. Or they can be universal, based on physiology. Or they can be culturally learned.

Anyone who has observed other people using websites has probably noticed that people often fail to notice what's right in front of their face. It's so common when we run usability tests that we have had to develop a standard patter to make sure people don't become embarrassed when we point out that the button they are looking for is in front of their noses.

It's an important issue for designers and product managers who want to make sure that certain key features of a site are noticed, only to be frustrated that their efforts are all but ignored.

Those of you who have studied usability will be familiar with eye tracking studies that tell us where the 'hot spots' and 'cold spots' on the screen are – what parts of the screen are most likely to attract attention, and which are not. The short version, for anyone interested, is that in cultures that read from left to right, we scan most web pages from top-left to bottom-right in a Z pattern. The best hot spots are in the upper left and lower right.

Based on recent observations in our UK labs, we'd like to propose a refinement to that common wisdom. In our labs, we notice that while users may still scan in a Z-shape, they typically don't scan the whole screen. Instead, they scan a smaller portion of the screen that we call the rectangle of interest, or ROI(!). The ROI includes the content area of the screen, and excludes the browser, tool bars, banner ads at the top, scroll bars, and sometimes titles, crumb trails, and other bits. One of the ways users focus on the task at hand is to find the rectangle most likely to have the content they asked for, and ignore everything else.

If you want something noticed, you need to insert it into the ROI. But here's the tricky bit. Users adapt to changing circumstances very quickly, and so if you put too much extra stuff at the edges (top/bottom/left/right) of the ROI, the user will unconsciously start to shrink the ROI.

Clever and intuitive designers with a commercial bent have already started to take advantage of this phenomenon by inserting ads and cross links inside the ROI. Here are our rules of thumb for designing with ROIs in mind.
• Assume that anything outside the ROI is unlikely to be noticed by most users who are focused on a task.
• If you want something besides the main content to be noticed in the ROI, make sure it is not at the top, bottom, left, or right edge of the ROI, and make sure it never fills up an entire vertical or horizontal space within the ROI.
• In addition to the main content, include only one or two items in the ROI – three at the most.

We're exploring further refinements to the ROI concept, looking at whether the ROI is different in different circumstances. We suspect it changes from platform to platform, and that it evolves as a user's experience increases. The first time a user looks at a web page, the ROI is probably bigger than for subsequent viewings. It may well be different on a home page than on other pages.

The details of how ROIs work will be filled in over time. In the meantime, keeping ROI in mind as you design and evaluate websites will help you ensure that you can help your users find the Mars Bar among the light bulbs.

I'd appreciate your views on this and related subjects. Have you noticed anything similar? Please write to me at aswartz@usability.serco.com.

by Andrew Swartz, Serco Usability Services
© 2004 Serco Limited, All Rights Reserved.

I'd like to thank my colleague Ben Weedon who worked on the initial project where we developed these ideas, and my colleagues Owen Daly-Jones and Marie Markowski who helped refine them.

Andrew Swartz
Principal Consultant
Serco Usability Services
www.usability.serco.com
020.7421.6499

Associated Link: Serco Usability Services

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