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by Geoff Hart
Previously published as: Hart, G. 2009. Attention deficits. Intercom September/October 2009:33—34.
The human brain is surprisingly ineffective at noticing what's going on around us, particularly when we're distracted. This has important consequences whether we're designing printed pages, help files, or Web sites, or documenting a user interface. In this article, I'll discuss three aspects of this problem and the constraints they impose on our designs.
Change blindness is what happens when we fail to notice that some aspect of our environment has changed. It's not surprising that subtle changes will escape our attention. Many of us are familiar with Microsoft Word's "customize" cursor: when you press Control+Alt+[hyphen], the cursor changes from the familiar pointer arrow into a large boldfaced minus sign, providing a visual cue that you're about to "subtract" the next toolbar icon or menu choice you click from Word's interface.
This follows interface-design best practices, which state that a tool's appearance should change to communicate a change in its purpose. But this design choice fails badly because the feature provides no additional warning (such as a confirmation dialog box) of what is about to happen. That warning wouldn't be necessary if users noticed the cursor change, but most don't; the archives of copyediting-l and techwr-l reveal dozens of plaintive queries from Word users who inadvertently deleted a handful of icons or menu functions because they didn't notice the cursor change—they were too busy focusing on their real work.
What's more surprising is that even drastic changes may be missed. An actor may change between scenes without the change being obvious, and Hollywood uses this to their advantage whenever they substitute a highly trained "stunt double" for a famous actor during a fight scene. But it also happens in the real world. In one experiment, a researcher stopped a pedestrian to ask for directions, and in mid-explanation, the explainer was interrupted; during the interruption, a second researcher replaced the original. About half of the test subjects never noticed, even though the second researcher didn't resemble the original. Watch the video yourself at the University of Illinois Visual Cognition Lab's Web site.
The phenomenon interferes with communication whenever a change happens that our audience may fail to perceive. In such cases, we must find a way to document the problem sufficiently clearly that anyone searching the Help file or the index can research the consequences of failing to notice a change and how to fix it. For example, Word's help file should (but does not) include a topic on "missing menu or toolbar items", with many synonyms used to help readers find it.
Change blindness was a key plot device in the movie version of The Andromeda Strain, in which a warning light changed from green to red and a main character failed to notice this change because they suffered from red–green colorblindness. Although changing an indicator from red to green (e.g., from stop to go, from bad to good) is a standard interface convention, red–green colorblindness is the most common form (it affects up to 10% of men in some ethnic groups; fewer than 1% of women show any form of color blindness). This means that up to 10% of our audience may be incapable of detecting the color change, quite apart from the proportion who simply miss it. One solution would be to use a green checkmark and red cross so that viewers who can't perceive the color difference can still perceive the shape change. For the most crucial changes, a popup warning message is better, as such messages are harder to ignore.
"Inattentional" blindness is a closely related phenomenon in we focus so much on one thing that we ignore something else (i.e., we exhibit inattention). Possibly the most famous demonstration of this phenomenon is a classic experiment by Christopher Chabris in which test participants were asked to watch two groups of people passing around basketballs: they were explicitly instructed to count the number of times the ball was passed between one group, a difficult task given the simultaneous presence of a second group of players and how quickly the ball and players were moving. Can you count the number of times the white players passed the ball? Try it before reading any further.
If you didn't notice the actor in the gorilla suit who walked through the scene, you're not alone. Astonishingly, roughly half of the test participants never noticed! "But I don't document gorillas or basketball!" you may exclaim. Fair enough. But you do document things that change, and you do produce documentation for people who are intensely focused on important tasks that consume a high proportion of their attention. Indeed, when people are focused on something other than what we're documenting, our documentation may be the least-important thing on their mind. We can't control the context in which our audience works, and we can't force them to pay attention to something important by interrupting their work with anything but the most crucial popup messages (as anyone who's cursed Windows Vista can attest), but we could at least try document the problem for the developers, and explain the problem and any possible solution to the users.
The split-attention effect is similar. Given that we only have a certain amount of attention we can focus on any given task, then the more things we must pay attention to, the less of our attention is available for each thing. This is why it's so dangerous to drive while using your cell phone: if you're sufficiently interested in the conversation to pay attention, you won't be paying attention to the more important task of driving safely. Combine this with change blindness and inattention blindness, and you can understand why many jurisdictions have made it illegal to drive while using your phone: the distraction can increase the frequency of collisions by up to 400%. A common legal loophole that lets you drive and talk if you use a hands-free phone, thereby keeping both hands on the wheel, entirely misses the point.
How does this phenomenon affect us? For one thing, we must learn to simplify our designs as much as possible to reduce the distractions vying for the audience's attention. Minimalist design is not just esthetically pleasing; it's also more "invisible", and avoids distracting users from what is truly important. Most Web site designers should learn this lesson; when every aspect of a Web page shouts equally loudly for attention, the entire page becomes a "tale told by an idiot, full of sound and fury, signifying nothing" (MacBeth).
Subtler problems arise. When designing data graphics, we're told to define the graph's line or color patterns in a key inside the graph rather than describing it in the caption. This advice is not just about esthetics; it significantly improves the viewer's ability to comprehend. If the patterns are described rather than shown, viewers must first comprehend the description and then translate the meaning into a visual pattern they can seek within the graphic; if they imagine the wrong meaning, they’ll search in vain. Even if the description is clear, viewers must switch back and forth between the caption and the graph each time they want to understand any pattern, wasting time and unnecessarily increasing the required mental effort. Placing all the information within the key eliminates the comprehension problem and the need to translate between textual descriptions and visual images.
Directly labeling the visual features of a graph is even more efficient: it eliminates the need to glance back and forth between the key and graph. This is why graphics labeled with callouts (explanatory text connected to key features by arrows) are easier to use and understand than graphics with numbered keys that describe the meaning of the numbers in a separate list. Comprehension is more direct, and we eliminate the need to search for the definitions of the numbers.
You can learn more about the split-attention effect at the Wikipedia.
Attention-deficit disorder is a hot topic, with debate raging over whether it's a true syndrome or merely pharmaceutical marketing propaganda. Perhaps the truth is that this is more of a spectrum than an absolute: the research in cognitive science described in this article suggests that everyone suffers from this disorder to a greater or lesser degree. As technical communicators, we can't prescribe Ritalin for our audiences, but we can certainly learn to minimize their distractions and help them focus on the task of completing their work.
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