The Mind’s Why

Goldfish and Human Attention Spans: They're a lot closer than you think.

Our attention spans are very simil -- let's get Chinese for dinner.

There it is, pinned to an office partition near you, under the Dilbert cartoon: a list of user-interface design guidelines. There’s been at least one copy stuck to a cubicle wall in every office I’ve ever worked at after 1996. Sometimes it’s Shneiderman’s, Eight Golden Rules of Interface Design. Sometimes it’s Jakob Nielsen’s Ten Usability Heuristics, or it maybe be one from Norman or Brown. If you hold these lists side by side, you’ll find they’re strikingly similar. Two separate rules on one list may be combined into one rule on another. The phrasing may be different, but the ideas are the same. Why is this?

The top five user experience superstars – Norman, Nielsen, Molich, Shneiderman, and Brown – helped create these guidelines years ago, right around the time your alphanumeric command line interface switched to a graphic one. Goodbye,  “rmdir c:\finances /s /q.” Hello, “drag to trash.”

What made these guys our industry’s MVPs? Unlike most people working in our field today, they had backgrounds in cognitive psychology, and they applied their knowledge of cognitive science to try to improve the design and usability of interactive computer systems. They weren’t interested in pretty or profitable; they were scientists, doing research independently, on how are brains solve problems.

Have you ever listened to Jakob Nielsen take 45 minutes to explain the mathematic formulas – N(1-(1-L)n) and others – that went into the study of the number of usability problems found in a usability test with n users where N is the total number of usability problems in the design and L is the proportion of usability problems discovered while testing a single user? I have. See, the typical value of L is 31%, averaged across a large number of projects he studied. You’re getting sleepy. Plotting the curve for L=31% gives the following result that we need to run qualitative test with 5 users.


Not even his “I’m feeling lucky” Google boxer shorts joke could wake most of us out of the stupor he created in that auditorium. And that’s because he’s not a poet, or and artist, or even a particularly good story teller. But Jakob is hardcore when it comes to his research analysis.

So when he came up with his top ten, he wasn’t out to differentiate himself from those who had gone before. He wasn’t trying to impose his own like and dislikes upon the HCI community. His rules call for things like clarity, consistency, error prevention, recognition, and recovery, just like the rules of those that had gone before him, because the those rules’ origins come from a common source. His guidelines, like his colleagues’, are based on human psychology: how we learn, reason, remember, and absorb information.

And this is useful information to those in our field because the human brain is often terribly inadequate when it comes to helping us understand things. Our color vision is minimal; mantis shrimp have 12 types of color receptors in their eyes – humans have three – and can also see  ultraviolet, infrared and polarized light. Our peripheral vision is limited; the average German Shepherd has a visual field of 250 degrees, while a human’s visual field is only 190 degrees. Our focused attention span is around eight seconds, only slightly above goldfish, whose attention spans last three seconds. And truckloads of neuropsychology test results show us that our own memories cannot be trusted, that our brains are constantly messing with our heads, and that we need to address these issues if we’re going help users successfully perform tasks using a computer interface.

Recently I’ve heard talk from those in our industry who don’t have a scientific background, of changing these rules to suit different business plans, marketing concerns, or design choices. “They’re old”, they argue, implying that, “old is bad.” And while it is important to keep current with new technology in our field, please let’s keep in mind that the original and best user-interface design guidelines were created by exploring the limits of the human brain and discovering what errors we are likely to make. As technology advances, and neuropsychologist learn more about how our brains work, we may find these lists of guidelines being augmented or updated. But for now, instead of trying to differentiate ourselves by making up our own personal list of interface guidelines based on our personal wishes, let’s focus on designing something to help our users cope with their brain’s limits and the corresponding errors that arise because of them.


For your cube wall:


2 Responses to “The Mind’s Why”

  1. andrew
    May 24, 2012 at 1:51 pm #

    you left out Daniel

  2. bethany lankin →
    May 29, 2012 at 4:18 pm #

    Thank you so much for taking the time to reply to my post. I’m flattered to be included in your class! Your comments have inspired me to keep contributing to this blog. Again, I thank you. Cheers!