There Should Be Limits to Usability

Innovating UX Practice

Inspirations from software engineering

A column by Peter Hornsby
April 5, 2011

People generally regard improving the usability of products or systems as a major part of our role as UX designers. While there are tradeoffs in all aspects of design, our assumption has generally been that products and systems that are easier to use are preferable to those that are harder to use. However, despite what seemed to be a common understanding, a number of articles have recently reported on research that suggests increased ease of use can be detrimental—specifically:

A study of text in different fonts found that information in fonts that were harder to read had better recall among test subjects than fonts that were easier to read. Researchers hypothesized that increasing the subjective feeling of task difficulty leads people to think harder about things.

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  • The Internet is changing how we think, read, and remember.

Nicholas Carr argues that the Internet is changing the way we think, moving us away from the single?minded concentration that is the consequence of our reading books—the previously dominant medium.

For a UX designer who considers usability to be key, this is counterintuitive. This column examines the research underlying these conclusions and looks at some lessons UX designers can learn from them.

The Massively Plastic Human Brain

“Neurons that fire together, wire together.”—Courchesne, Chisum, and Townsend (1994)

For generations, we have debated the influence of nature versus nurture and which is more important in determining who we are:

  • nature—the innate qualities we are born with
  • nurture—our personal experiences

Research into the workings of the human brain shows that both nature and nurture are key factors in determining who we are. While we are all born with a brain that has certain regions that are devoted to particular types of mental processing, the structure of the brain constantly changes as the brain rewires itself in response to what we learn from our experiences—making stronger connections between some cells and weakening connections between others. This change in structure is called plasticity and happens as a result of all of our experiences—for example, as we form habits from our day-to-day experiences.

This plasticity is most apparent in extreme cases, when people lose limbs or senses. In the case of a lost limb, this rewiring of the brain gives rise to the temporary sensation of a phantom limb, as the part of the brain that was previously responsible for processing information from the missing limb instead processes sensations from another part of the body.

London taxi drivers, who are famous for The Knowledge—an intimate acquaintance with the streets of London within a 6?mile radius of Charing Cross—provide a much less extreme example of the plasticity of the brain. Research has shown that the hippocampus—the area of the brain that is associated with navigation—grows larger as drivers spend more time on the job.

While the brain’s plasticity is the basis of our ability to develop skills and knowledge, it is also true that, if we do not use parts of our brain sufficiently, the associated neural pathways start working less effectively. This is as true for user experiences as it is for any other experiences an individual has.

The Medium Is the Message

It is not only what we experience and learn that matters; how we experience and learn is also vitally important. Human beings have always used tools, or technology, to expand their capabilities. As Marshall McLuhan noted, “the medium is the message.” Therefore, how we experience a message—the medium—influences how we perceive and react to it. Research shows that the brains of illiterate people are structurally different from those of people who are literate. Similarly, research on monkeys who are being trained to use tools has shown that strong growth occurs in the visual and motor areas they have used to control the tools. As we use tools, particularly knowledge?based tools, our brains adapt to them.

For example, compare the task of creating a hierarchical file structure using a command-line interface (CLI) versus using a graphic user interface (GUI). Using the DOS CLI, creating a file structure involved using the md < directory name >, or make directory, command and the cd < directory name >, or change directory, command. Using the Unix CLI, users can string commands together using shell scripting, giving them vastly greater control over what they are doing. Conversely, creating a file structure using a GUI requires a combination of mouse and keyboard actions and typically takes longer. While the GUI is simpler for a novice, it is also more restrictive and less powerful—for performing certain tasks—than its command-line cousins.

We can draw a comparison between logographic languages such as Chinese and alphabetic languages like English. Chinese children grasp the basics of writing in Chinese more slowly than their Western counterparts learn to write, but once they have grasped those basics, their rate of learning is much greater. The initial investment of Chinese children in learning to write is more substantial, but provides a better foundation for learning later in life.

Implications for UX Design

So, what does all of this mean for UX designers and their quest to make things ever?easier to use? First and foremost, there are domains where forcing the brain to work harder is a bad idea—for example, in emergency situations, when a user interface must present users with only the most relevant information to allow them to make a quick decision.

On the other hand, consider one of the most common types of applications: word processors. A word processor that highlights users’ spelling and grammar mistakes might lead users to assume that the application will capture all of the errors they make. As a result, people might employ the part of their brain that they use in checking spelling and grammar less often, and over time, disuse of that part of their brain could lead to a weakening of its neural connections. In other words, employing that part of their brain less leads to a reduction in their ability to spell well and use proper grammar.

The computing ecosystem is a double-edged sword for UX designers: On the one hand, we employ common interaction models, processes, icons, and so forth in our designs that, in most cases, let users quickly get up to speed in understanding the operation of multiple applications. So, users’ knowledge is highly transferable between computing systems.

But this commonality has, at the same time, reduced the flexibility with which users can respond. Because applications mostly work the same way, users’ brains are conditioned to go through particular steps to resolve similar issues. This is, in part, the success of the GUI paradigm. We can be productive within that paradigm, but it also shapes our thinking about what we can do. We have realized the goal of making computing power accessible to everyone. Now it’s time for a new goal: evolving computers into tools that help us to be more productive in the short term, without eroding our own capabilities over time. 


Courchesne, E., H. Chisum, and J. Townsend. “Neural Activity-Dependent Brain Changes in Development: Implications for Psychopathology. Development and Psychopathology. Volume 6, 1994.

Director at Edgerton Riley

Reading, Berkshire, UK

Peter HornsbyPeter has been actively involved in Web design and development since 1993, working in the defense and telecommunications industries; designing a number of interactive, Web-based systems; and advising on usability. He has also worked in education, in both industry and academia, designing and delivering both classroom-based and online training. Peter is a Director at Edgerton Riley, which provides UX consultancy and research to technology firms. Peter has a PhD in software component reuse and a Bachelors degree in human factors, both from Loughborough University, in Leicestershire, UK. He has presented at international conferences and written about reuse, eLearning, and organizational design.  Read More

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