Picture someone in their seventies trying to unlock a banking app with their fingerprint. It used to work. Now it fails, again and again.
Nothing is wrong with the app. Nothing is wrong with the phone. Their skin changed. With age, fingerprints get drier and shallower, and the sensor stops recognizing them. So they type a password with one finger, slowly, while the app warns that this is "less secure."
The product was designed for a user. It just wasn't designed for a body.
Our personas don't have bodies
Most product teams I've worked with build personas the same way: a name, an age range, a job, a goal, a frustration, maybe a stock photo. "Laura, 34, marketing manager, wants to pay faster."
Laura has needs and motivations. What Laura doesn't have is hands, eyes, skin, fatigue, a commute, a cracked screen or a baby on one arm.
That's not an accident. Western thought spent centuries separating mind from body and putting the mind in charge, and software inherited the habit. We design for a rational user who perceives a screen, decides and clicks. The body is assumed, invisible and, conveniently, always in perfect condition.
But every interaction goes through the body first. Before anyone understands your UI, they have to see it, reach it, touch it and hold it steady. The body is the first interface. Our screens are the second.
Bodies change, and products don't notice
Philosophers like Merleau-Ponty argued that we don't have a body that perceives the world; we perceive the world through a body, and that body shapes what we can perceive. Marshall McLuhan, from a different angle, described media and interfaces as extensions of the body.
Put those together and you get an uncomfortable idea for product teams: if interfaces extend the body, they inherit its limits. And bodies are not stable.
- They age. Fingerprints fade, near vision declines, fine motor control gets less precise.
- They get tired. The same person taps less accurately at 11 p.m. than at 10 a.m.
- They're situated. Direct sunlight, a bumpy bus, cold hands, gloves, one free hand.
- They're temporarily or permanently different. A broken wrist, a tremor, low vision, color blindness.
When I built vehicle interface prototypes, this was impossible to ignore. A driver's finger never lands where you expect, because the car is moving and vibrating. Their eyes can only leave the road for a moment. The "user" is a body in motion before it is a mind making choices.
Interfaces are political, too
Here's the part we don't say out loud: when a product only works for one kind of body, someone chose that. Usually not on purpose. It happens through priorities, deadlines and a test group of colleagues who are all 25 to 40, sitting at a desk, with good eyesight and the latest phone.
Over time, users also adapt to us. They learn to squint, zoom, double-tap and retry, and we read their silence as satisfaction. The people who can't adapt, often older adults and people with disabilities, simply leave, and they rarely show up in the metrics as anything but churn.
Sensory ethnography: research that includes the body
Interviews and usability tests are good at capturing what people say and what they click. They're bad at capturing what their bodies go through.
Sensory ethnography, a method from anthropology (Sarah Pink's work is a good starting point), studies experience through the senses: how something feels in the hand, sounds in a noisy room, looks in the sun. In product terms, that means doing research with users in the places where they actually use your product, paying attention to posture, light, noise, movement and touch.
You don't need a research budget to start. Some things I now do or recommend:
1. Give personas a body and a context.
Add a line for each: "Uses the app with one hand while holding a child," "Reading glasses, often forgets them," "Opens the app on the bus, standing." It changes design discussions immediately.
2. Test in the wild, not at your desk.
Use your own product outside, at noon, at full brightness and at low battery. Use it walking. Use it with a cold hand, or a glove. You'll find bugs no linter will.
3. Always ship a fallback for biometrics.
Fingerprint and face unlock are great until they aren't. Make the fallback fast and respectful, not a punishment labelled "less secure."
4. Treat target size as a floor, not a goal.
WCAG 2.2 asks for at least 24 by 24 CSS pixels for targets at level AA, and 44 by 44 at level AAA. For anything used while moving, go bigger.
5. Respect the body's settings.
Font size, prefers-reduced-motion, prefers-contrast, dark mode: these are the body talking to your interface. Honor them by default.
@media (prefers-reduced-motion: reduce) {
* {
animation-duration: 0.01ms !important;
transition-duration: 0.01ms !important;
}
}
6. Watch, don't only ask.
When you do research, look at how people hold the phone, where their thumb rests, when they lean in or squint. The body tells you things users won't think to say.
Design for the body that will use it
Art can ask for effort. A painting can be difficult and still be worth it. Interfaces don't get that privilege: they have to work for people of every age, ability and circumstance, on their worst day, in their worst light.
That person in their seventies didn't get worse at banking. Their body changed, and the interface didn't change with it.
If we start treating the body as the first interface, that's a bug we can actually fix.
This piece grew out of an essay I wrote during my master's in Communication and Digital Humanities, mixing anthropology of the body with UX. It's part of my series on the human side of interfaces.
Where has your own body made a product fail you? Tell me in the comments.
References
- Merleau-Ponty, Maurice. Phenomenology of Perception. 1945.
- McLuhan, Marshall, and Eric McLuhan. Laws of Media: The New Science. University of Toronto Press, 1988.
- Pink, Sarah. Doing Sensory Ethnography. SAGE, 2009.
- Scolari, Carlos. Las leyes de la interfaz. Gedisa, 2018.
- W3C. Web Content Accessibility Guidelines (WCAG) 2.2, Success Criteria 2.5.5 and 2.5.8.
Top comments (1)
Embodied interaction is a useful reminder that accessibility cannot be an adaptation pass after a visual design is finished. The starting question should be what movement, attention, and sensory assumptions the interface makes—and whether each has an equivalent path. That reframes inclusion as a product constraint rather than a special feature.