If you’ve spent enough time behind the one-way mirror during usability study sessions, you begin to notice some interesting things. While we’ve been at it for much longer, we have collectively run 4,947 usability study sessions in the past three years, our largest clip to date!
Regardless of whether the product is intended for surgeons, nurses, pharmacists, caregivers, or patients, many of the same human behaviors appear again and again. The longer you’ve been in the game, the more you say, “We’ve seen this before.”
These aren’t formal scientific laws, nor do they apply in every situation. Rather, they’re recurring observations that have shaped how we think about human factors engineering and how we design a usability study for our clients.
Users rarely read instructions as much as sponsors expect
I’m guessing most people reading this know this to be true, but it is a common surprise for first-time sponsors.
When participants receive a new device, sponsors often assume they’ll carefully review the Instructions for Use (IFU) before interacting with it. In reality, many participants do, and many others users begin by looking at the device itself. They may rely on prior experience, visual cues, labeling, and intuition to determine what to do next.
This isn’t because users are careless. It’s because they’re behaving much as they do in everyday practice. Experienced clinicians, in particular, frequently approach new devices through the lens of products they’ve used before.
That observation has important implications. If safe use depends on users carefully reading several pages of instructions before beginning, the design itself may deserve closer scrutiny. Instructions remain an important risk control, but they should complement good design rather than compensate for poor usability.
They use QR codes to instructional videos even less
Over the past several years, we’ve seen more manufacturers include QR codes that link to instructional videos. The intention is understandable. Videos can be an excellent way to demonstrate setup or technique.
The reality, however, has been less encouraging.
During a usability study session, participants rarely interrupt a task to scan a QR code. I’d bet that many don’t even notice it. Even when they do notice it, many simply continue with the task instead.
Interestingly, if participants genuinely need help, they’re often more likely to search Google or YouTube using their own terms than to scan a manufacturer’s QR code. Whether that’s due to familiarity with search engines, trust, convenience, or simple habit is difficult to say, but it appears consistently enough to be worth considering during product development.
The existence of an instructional video should not be viewed as evidence that users will actually watch it. If you really want users to watch videos, it’s likely you have to force them to watch it or make incredibly obvious and accessible.
Anxiety changes behavior
Medical devices are often used in stressful situations.
Ironically, participating in a usability study can also be stressful.
Participants know they’re being observed. They may worry about making mistakes or appearing incompetent, particularly when they’re experienced healthcare professionals.
Some participants slow down dramatically. Others rush. Some become unusually hesitant, while others act overly confident in an attempt to appear capable. None of these responses necessarily reflect how they would behave in actual clinical practice.
This doesn’t mean we should eliminate anxiety entirely (as if we could). Some degree of stress is unavoidable and, depending on the intended use environment, may even improve realism. However, researchers should recognize that participant anxiety is not simply background noise. It can meaningfully influence study outcomes and should be considered when interpreting results.
Addressing it can change the quality of the study
We often think of human factors studies as evaluations of products. In reality, they’re also interactions between people.
Participants quickly form impressions about the moderator, the sponsor, and the overall study environment. Small details like a warm welcome, clearly explained expectations, whether mistakes are normalized, and whether they feel genuinely respected can have a surprisingly large impact on the session.
When participants feel judged, they become cautious. They may second-guess themselves, hesitate before acting, or look for reassurance they wouldn’t seek in real use.
When participants feel comfortable, they’re more likely to behave naturally, reveal their thought processes, and recover from mistakes in realistic ways.
Creating psychological safety isn’t simply about being polite. It’s an important part of collecting valid data.
User confidence interacts with device intuitiveness
When a device is genuinely intuitive and aligns well with users’ expectations, confidence is usually beneficial. Confident users move efficiently through tasks, make appropriate decisions, and rarely need to stop and verify every action. The user interface supports their mental model, allowing them to focus on the clinical task rather than the mechanics of operating the device.
However, we’ve also observed a different pattern when a device appears intuitive but contains subtle usability issues.
In these situations, confidence can actually work against the user.
A familiar-looking connector may function differently than expected. A button may resemble a commonly used control but perform a different action. A screen layout may encourage an assumption that turns out to be incorrect. Because users feel confident that they already understand the interface, they often move quickly, relying on experience and intuition rather than carefully verifying each step. As a result, hidden usability problems tend to surface quickly.
By contrast, less confident users often behave quite differently. They slow down, examine labels more carefully, consult the IFU when uncertain, and deliberately verify their assumptions before proceeding. Although this approach may be less efficient, it can reduce the likelihood of errors on devices with non-obvious design features.
This observation has an important implication for product development. A usability study in which every participant proceeds cautiously may not reveal the same issues that emerge when users feel comfortable enough to rely on intuition. In some cases, a confident user provides a more demanding test of the interface because they interact with the product in a way that more closely resembles experienced, real-world use.
Ultimately, the goal of human factors engineering is not simply to create confident users. It is to create interfaces that deserve users’ confidence. When users can safely rely on intuition, confidence becomes an asset. When intuition leads them astray, confidence can expose design weaknesses that might otherwise remain hidden.
Final thoughts
Every usability study is unique. Different users, different products, different clinical environments, and different risks all shape how people interact with medical devices. Yet after years of observing participants across a wide variety of usability study sessions, certain patterns tend to emerge!
These observations aren’t rules, nor do they predict what will happen in every study. Rather, they serve as reminders that human behavior is remarkably consistent in some ways and surprisingly variable in others. People rely on prior experience. They make assumptions. They adapt. They recover from mistakes. They respond to stress, confidence, uncertainty, and the environment around them in ways that are often understandable once viewed through the right lens.
Perhaps the most valuable lesson we’ve learned is that meaningful insights rarely come from simply counting use errors. They come from carefully observing behavior, understanding the context in which decisions are made, and asking why capable people behaved the way they did. Those answers often reveal opportunities to improve a design long before a product reaches patients or clinicians.
Every participant teaches us something. While individual findings may be specific to a particular device, the underlying principles of human behavior often extend far beyond any single project. Those recurring lessons continue to shape how we design studies, interpret results, and ultimately help our clients develop medical devices that are not only compliant, but intuitive, resilient, and safe for the people who use them every day.
