There is a moment, familiar to anyone who has ever stepped out of a dark restaurant into noon sunlight, when your phone becomes a very expensive mirror. You tilt it, cup a hand over it, squint at the ghost of a text message, and finally give up and walk somewhere shadier to read three words. Nothing is wrong with you. Nothing is wrong with the phone, either — it is performing exactly as designed, for a person sitting still indoors with both hands free and twenty-year-old eyes. The failure is that you are not that person, and for the next four minutes, neither is anyone else on the sidewalk.
This is the thing accessibility discourse keeps almost saying and then politely swallowing: the “normal user” that interfaces are built around is a statistical fiction who exists only in the demo. The rest of us cycle in and out of the excluded group constantly — with a broken wrist, a sleeping baby on one arm, a dead earbud on a loud train, a migraine, a new pair of bifocals, or just a body that has been alive for a while. The World Health Organization estimates that 1.3 billion people — about 16 percent of the world’s population — experience significant disability, and its own fact sheet opens with the observation that disability is “part of being human and is integral to the human experience.” That is not a soft sentiment. It is a description of the user base.
The spectrum nobody escapes
The cleanest articulation of this comes from an unlikely source: a corporate design methodology. Microsoft’s Inclusive Design toolkit, developed under Kat Holmes — who expanded the argument in her 2018 book Mismatch: How Inclusion Shapes Design — maps any given limitation across what it calls the Persona Spectrum. A person with one arm has a permanent constraint. A person with a broken arm has a temporary one. A parent holding an infant has a situational one. Same problem, three durations. The toolkit’s first principle is “recognize exclusion,” and its pitch is that solving for the permanent case produces results that extend to everyone — the temporary and situational cases being not edge cases but the same case, wearing a watch.
What’s quietly radical in this framing is what it does to the word “normal.” If a constraint can be permanent, temporary, or situational, then the axis that matters isn’t who has it — it’s when. Everyone has abilities and limits, as the methodology puts it, which is a bland sentence until you sit with it: the limits are the constant, the abilities are the variable. Permanent disability is simply the sustained version of an experience everyone has intermittently. The person in the wheelchair and the person on crutches and the person carrying a sofa up the stairs are not three categories of human. They are one category, sampled at different moments.
The fiction in the demo
The design industry has known a version of this for a long time. In The End of Average, Todd Rose recounts how the U.S. Air Force, measuring thousands of pilots against an “average” body in the mid-twentieth century, discovered that essentially no individual pilot was average across all dimensions — the average was an artifact of aggregation, a person made of arithmetic. The fix was not to find better average pilots. It was to make cockpits adjustable. Software mostly skipped this lesson. The cockpit is still fixed; it’s just a checkout form now.
You can watch the fiction do its work in any product review. Someone demos a feature: seated, rested, on fast Wi-Fi, both hands free, screen at full brightness in a dim room, fluent in the language, undistracted. The feature passes. Then it ships into a world of glare and deadlines and tremors and toddlers, and the failure gets logged — if it gets logged at all — as an accessibility gap, a minority concern, a ticket for later. But the gap isn’t in the minority of users. It’s in the imaginary user the thing was tested against. Designing for the fiction is what turns ordinary moments into failures.
This is why the curb-cut effect keeps repeating itself in domains that have nothing to do with wheelchairs. The term comes from legal scholar Angela Glover Blackwell, writing in the Stanford Social Innovation Review in 2017, about the ramps cut into sidewalks — first in Kalamazoo in 1945, then famously in Berkeley in 1972 after disability activists poured their own guerrilla concrete — that turned out to serve nearly everyone. Blackwell cites a Sarasota mall study finding that nine out of ten “unencumbered” pedestrians go out of their way to use a curb cut. Curb cuts were built for a small group and adopted by the majority, not out of solidarity but out of convenience. Captions follow the same arc: designed for deaf viewers, now the default for anyone watching video on a silent phone in a waiting room — which is to say, everyone, eventually, daily. The architect Ronald Mace called the underlying principle universal design: products and environments “usable by all people, to the greatest extent possible, without the need for adaptation.” Mace, who used a wheelchair, founded what became the Center for Universal Design at NC State in 1989. He wasn’t proposing generosity. He was proposing accuracy.
A necessary discomfort
It’s worth being honest about where this argument can curdle. The phrase “temporarily able-bodied” circulates in disability-rights discourse precisely as a provocation — a reminder that the able-bodied are merely between episodes — and some disabled writers have pushed back on it, arguing that flattening a broken wrist and a lifetime of paralysis into one spectrum can erase the difference between inconvenience and lived experience. They’re right that a six-week cast teaches you nothing about fighting an insurer for a power chair, and that “everyone is basically disabled” can become a way of hearing no one in particular. The point of the spectrum is not that all exclusions are equal. It’s that the mechanism is shared: disability arises when a body meets an environment that refuses to accommodate it, and environments refuse intermittently, at random, to everyone.
Which suggests a different standard than the one accessibility usually gets judged by. The question isn’t whether a product serves the disabled — a fixed group, somewhere else, to be accommodated later at some cost. The question is whether it serves people on their bad days, their busy days, their aging days, which is to say whether it serves people at all. The demo user will never file a complaint, because the demo user does not exist. The person squinting at their phone in the parking lot does. She is not an edge case. She is the base case, caught in the brief honest interval before she forgets again that the normal user was never her.