Big targets and no mistakes: why the parent's screen has nothing to break

Ask a designer to make an app usable for an 80 year old and the first thing they’ll do is make the buttons bigger. It’s the right instinct and it’s in every guideline. It’s also where most of them stop, and stopping there misses the part that actually matters.

This is the last of four posts on the research behind the senior screen. It’s about hands, and about fear.

Fitts’s law, and hands that have changed

In 1954 Paul Fitts showed that the time it takes to hit a target depends on two things: how far away it is and how big it is. Small, distant targets take longer and get missed more often. The result has held up for seventy years, across mice, fingers and styluses, which is rare for anything about human behavior.

On a phone, it means a small link in the corner is slower and riskier than a big button in the middle. That’s true for everyone. What differs is what a miss costs.

Vision is the aging change everyone knows about. Hands are the one people forget. Arthritis is common, tremor gets more common with age, and fine control drops. Dry fingertips don’t always register on a touchscreen at all, which is why some parents tap three times and get nothing. The confident single tap a 30 year old makes without looking can become a slower, less certain press, and a finger that lands a few millimeters off a small target hits whatever is next to it.

Stack that on Fitts’s law and small controls on a senior’s phone aren’t just slow. They sometimes do the wrong thing. On a caregiving app, the wrong thing might be canceling Thursday.

The 44 point rule

The guidelines agree on a number. Apple’s Human Interface Guidelines ask for tap targets of at least 44 by 44 points. WCAG, at its strictest AAA level, asks for 44 by 44 pixels. Plenty of apps meet it for their main buttons and quietly break it for the small stuff: the x that closes a sheet, or the toggle tucked inside a settings row.

The few things you can tap on your parent’s side of Marlow are big. That was the easy part, and on its own it isn’t very interesting. Every well meaning “senior mode” ever built has big buttons.

The fear of breaking it

It’s well established in the accessibility literature that older adults are more reluctant to explore an interface when they’re afraid of breaking something, and slower to recover from an error once it’s happened. The CREATE center’s researchers, who have spent years on older adults and technology, find that anxiety and low confidence predict whether a technology gets used better than age does, and that lowering the stakes matters more than simplification on its own.

Read those together and big buttons stop being enough. A big button that can cancel an appointment is still a button that can cancel an appointment. Plenty of parents have already lived the rest: the one time she touched the screen, something happened to the calendar, her daughter had to sort it out, and she’d rather not go through that again.

That’s the failure. Not the mistap itself. The phone on the counter nobody looks at, because looking might lead to touching and touching might break something.

Why the answer wasn’t bigger buttons

So on the senior side we removed the possibility. There is nothing on your parent’s screen that changes the schedule. She can’t add an appointment, and she can’t cancel or move one. There’s no account to sign out of and no password to get wrong. Nothing she taps by accident can touch the schedule. The screen is something to read, the way a wall calendar is something to read.

One tap on her phone does record something, and you should know which. The medicine reminder asks whether she’s taken it, and a tap says yes. That’s a note for the family, not a change to the schedule. It’s also the one place an accidental tap leaves a mark, so if your parent is likely to press things without meaning to, keep whatever you use now to check on medicines.

That’s the bet. If nothing can break, there’s less to be afraid of, and a parent who isn’t afraid of the phone is more likely to pick it up. The lock screen and the home screen widget carry the same facts, when to be ready and who’s coming, so most days she doesn’t need to touch anything at all.

It’s a bet about a particular parent. If your father runs his own calendar and would find a screen he can’t touch insulting, this isn’t for him, and nothing stops you inviting him into the circle like anyone else. The post on why the senior screen has no buttons covers what this rules out. The short version: it’s a display for her and a tool for the family, and those aren’t the same thing at two type sizes.

Read only, enforced below the app

Hiding buttons doesn’t make an app safe. It makes it look safe. Apps have bugs, and a hidden control is still there for a bug to trigger.

So the read only rule on the senior side isn’t a matter of what’s drawn on screen. Your parent’s phone is paired to the family’s circle as its own account, and that account is granted read access at the database, not write. The server refuses a change from it. If the app on her phone had a bug that tried to move an appointment, the request would be turned down before it touched anything. The permission lives in the one place a tap can’t reach.

That’s what lets the family stop worrying about it. There is no sequence of taps, deliberate or accidental, that deletes Tuesday. The senior side page says the same thing in fewer words.

What we haven’t tested

We followed the published guidance on target size and on the fear of errors. We didn’t run a study of our own, and we can’t see whether your father ever mistaps, because Marlow runs no analytics. We ask families, and the parents using it are the ones who tell us when something is awkward. If yours finds the screen hard to use, tell us. That’s the whole feedback loop, and it’s the one we’re comfortable with for someone who never agreed to be measured.