Fitts’s Law

Fitts’s Law has been known since Paul Fitts first proposed it in 1954. Wikipedia has a detailed exposition of Fitts’s Law. In essence, it says that “the time required to rapidly move to a target area is a function of the distance to the target and the size of the target.” “Targets that are smaller and/or farther away require more time to acquire.” While this has many applications in industry, we are particularly interested in computer applications, and, specifically, usability of medical software.

Fitt's Law Diagra

Fitts’ Law

We can expand this definition a bit, by being engineers and designers and critics rather than scientists. It is reasonable to assume that the harder something is to do, the more fatigue – mental, physical or both – it will entail.

We know from the Pen-Ivory experiments that paging is better than scrolling. Many vendors are tied to the idea of resizable windows, both due to laziness, and due to user demands to use the maximum space on their monitors. But as with lines of text, increasing the window size may decrease readability and usability.

Many medical applications present us with pages filled with a massive number of small targets. We know that a larger the number of choices on a screen means a more cognitively-tiring process in selecting among them. But there is another dimension to such cluttered pages; when clickable items are widely separated on the page, Fitts’s Law tells us that using the page could be made easier, in both physical and cognitive terms, by decreasing the number of clickable items on the page and increasing their clickable target size. As Strunk and White says: “omit needless clickable items.” (I paraphrase slightly.)

Fitts’s Law is interesting. But for medical applications, where a wrong click may have consequences far beyond navigating to the wrong page, it’s something all developers should keep in the front of their minds. Wrong clicks can kill.



In Icons, Pedagogic Vectors, Forms Design and Posture we briefly discussed icon design. (Icons, in this context, meaning the sketch-pictures on buttons that you can click.) The bottom line was that it’s hard to learn and remember what icons stand for.Icon

In Performance, Data Pixels, Location, and Preattentive Attributes we discussed how icons should be recognizable by preattentive attributes, so there is no Cognitive Friction to overcome when selecting the right icon on which to click.

In Color, we discussed the role of color in icons, coming down to the idea that icons shouldn’t use color, and should be grayscale. Read the rest of this entry »


Signal-to-Noise Ratio

finding the numbers can be hard

finding the numbers can be hard

I work at the University of Pittsburgh Medical Center. UPMC has prioritized IT, and compared with many other academic medical centers, the IT department is fairly well-funded and well-staffed. The central IT umbrella spreads wide, including 16 major hospitals and numerous other facilities. UPMC uses Cerner for an inpatient electronic medical record (EMR) (and for outpatient settings). For clinical charting in the ED, we use Cerner’s PowerChart 2G, dictating into it using Dragon speech recognition. PowerChart is pretty klunky, as are its templates, and in our ED we use our own very simple PowerChart templates, basically a blank page into which to dictate.We in the ED built some standard templates and macros in Dragon, and docs, including residents, can customize or add new templates or speech macros as they wish, which speeds up dictation quite a bit.

However, we actively discourage the use of the PowerChart templates. Why? Because PowerChart templates have a seductive feature that the vendor and our IT people used to tout. But as it turns out, that feature trashes the signal-to-noise ratio of the chart.

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The Master said: “When the noble man eats he does not try to stuff himself; at rest he does not seek perfect comfort; he is diligent in his work and careful in speech. He avails himself to people of the Way and thereby corrects himself. This is the kind of person of whom you can say, ‘he loves learning.’” [Confucius: Analects 1:14]

User interaction design is now the victim of fashion, or perhaps worse, fads. First, we had what artists call trompe-l’œil, which is creating a 3-D impression by skillful painting in 2-D. A great recent example is a painted concrete bridge in Frederick, Maryland. The computer equivalent of the Frederick Community Bridge is skeuomorphism. Some say that computer interfaces took skeuomorphism to excess. Many cite recent versions of Apple’s iOS operating system; others cite Windows 7’s “Aero” interface.

Most obviously with the Windows 8 “Metro” interface, an anti-skeuomorphic design fad took off. Some tout the “flat design” in Apple iOS 7. Others say that Apple stole the idea from Android, from the highly-lauded Windows Phone, and the Windows 8 “interface formerly known as Metro” (Microsoft removed the “Metro” label and now just calls it the Windows 8 interface; most of the rest of us still call it Metro.) UXmatters has an entire post about it.

Flatland: A Romance of Many Dimensions

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A wireframe document for a person profile view

A wireframe document for a person profile view

A common technique for prototyping computer screens is to use wireframes. A recent article in UXmatters discusses wireframes, and asks whether wireframe prototypes are used by program designers as a substitute for real collaboration.

That’s a good question. But I think this is a better one: is showing wireframes to people a poor substitute for figuring out what users need to do, and then designing and refining a workflow process that works for them?

Wireframing, also known as paper prototyping (because it can all be done on paper, without wasting a single electron) can be an effective tool during design. However, it is not a substitute for sitting down with some of each class of users, using anthropological techniques to document the tasks they are accomplishing as they work, and using personas to guide the design of the computer-based work process for these classes of users, and then going back and using discount usability testing to refine the process.

Wireframes are good but not a substitute for either collaboration or task analysis.

//commented out L sidebar 7/26/11 //