Humans Have Limited Working Memory
Consider a very common, high-level EHR design. The screenshots that follow are from a particular EHR, but many vendors use a similar design.
A row of clickable tabs at the top of the screen is used to designate the different categories of data that make up the patient visit. When a tab is clicked, the window for that category of data opens to full screen size. The tabs can be clicked in any order.
The screenshot above shows what I would see after having clicked on the History of the Present Illness (HPI) tab and having entered some data.
If I were then to click on the History (Hx) tab and enter some data, the new screen would look like the one above. The HPI data is no longer visible because the HPI window automatically closes when the Hx tab is clicked.
This EHR design is completely logical. It is also completely usable, if usability is defined as being able to easily navigate from one part of the record to another with a single click. In fact, it is a totally reasonable design if it weren’t for one problem — humans have absolutely terrible short-term (working) memory.
It used to be thought that humans could retain about seven unrelated elements in working memory, but recent work suggests that the actual number is more often in the range of four to five. In contrast, a modern computer has no problem retaining thousands of unrelated data elements in random access memory.
Given our severe limitation in working memory, this EHR design doesn’t work very well. Every time I click on a new tab, the previous window closes and that data is no longer visible. I have to carry that information in my head. Furthermore, the row of tabs itself contains no information. It just serves as a navigation tool.
In other words, this design is based on how a computer — not a human — thinks. It is a computer-centered, not a user-centered design (see my first post).
As a clinician, I need to devote my full cognitive resources to my patient’s health issues. I need to be able to retrieve information from any part of the record quickly and effortlessly. While completely logical, this very common EHR design just doesn’t do a good job of extending my working memory. From personal experience, I can tell you that using a system like this is enough to drive you crazy.
So what’s the alternative? The alternative is to design an EHR based on what humans are good at — using our visual system to make sense of the world. The data needs to be organized spatially, assigning each module to a fixed location on the screen the way that T-Sheets and other paper forms do (see my previous post). Instead of making the overview of patient data just a row of information-less tabs, display the actual data in a one- or two-screen view, allowing the clinician to see the information rather than forcing him to remember it.
Of course, every design requires compromises. If you decide to use a compact, fixed spatial layout for your high-level design, then you need to solve the twofold problem of what to display in the default view and how to display more information on demand.
In my next post, I will present an example of one widely used EHR design solution to this problem.
The Problem with Scrolling
Rick Weinhaus MD practices clinical ophthalmology in the Boston area. He trained at Harvard Medical School, The Massachusetts Eye and Ear Infirmary, and the Neuroscience Unit of the Schepens Eye Research Institute. He writes on how to design simple, powerful, elegant user interfaces for electronic health records (EHRs) by applying our understanding of human perception and cognition. He welcomes your comments and thoughts on this post and on EHR usability issues.