On Control Center’s Norman Door problem

Michael McWatters, on Medium, illustrating the Norman Door problem with iOS 10’s split-up Control Center:

You swipe up to reveal the Control Center, then swipe sideways between the two panels. This has created a couple usability problems:

  • The only indication that there’s another hidden panel is the carousel-style dots at the bottom of the screen; these are tiny and easy to miss, so users may not even know there’s more than one panel.
  • Once you swipe to a given panel, you have to swipe in the opposite direction to go back, and this is where the Norman Door problem arises.

Here’s how this plays out: you swipe up to reveal the Control Center’s Home panel, the default. You need the Now Playing panel, but you’re not sure where it’s hiding, so you swipe right. Wrong! That’s a dead end, but you had a 50% chance so better luck next time!

Later, you want to go back to the Home panel, but you’ve forgotten whether it’s off screen to the left or right, so you swipe left again. Wrong! Another dead end. You swipe right and you’re in the right place.

His proposed solution:

[…]treat the two panels as an infinite alternating carousel: no matter which panel you’re on, the other panel is off-screen on either side.

While reading Micheal’s article, I was constantly reminded of the way Apple Music solves this problem of indicating ‘There’s more content to the other side’ by showing the user just a bit of said content from the edge of the screen. (If you’re an Apple Music subscriber, open the Music app and switch to the For You tab to have a look for yourself.)

Instead, Micheal proposes the edge-revelation method I just described when his readers pointed out that people who use Home-Kit devices have a third Control Center panel. In this case the infinite carousel solution breaks because the user is forced to either hit-and-try, or memorisation (until they’re habituated—of course) to get to the panel they want.

But I think the infinite-carousel solution is flawed even if there weren’t the problem of a third panel. Here’s why:

  • The metaphor being used by this panel/screen-swipe gesture is that of flipping the pages of a book. (For iOS apps, the related element is called ‘UIPageViewController’.) It has a sense of familiarity with the analog world where flipping (swiping) forward gets you to the ‘next’ object. Keep going ‘next’ and you reach the end. You never encounter the same object again—like you would in a carousel. If you’re thinking, ‘Yes, but people are comfortable with the digital world now; designers can come up with metaphors native to the digital world’, you’d be right. Allow me, then, to put forth my second argument.
  • Doing an infinite-carousel would break familiarity with other parts of iOS. Consider, for example, the iOS lock-screen—it uses the same paginated control. Lock-screen (with notifications) at the center, widgets and camera to the left and right, respectively. An infinite carousel solution with these screens seems incredibly bleak—even if you chose just two screens.
    It would be confusing for a user to have to remember two pagination paradigms—one that scrolls in a loop and one that doesn’t. (I suspect this could be the reason why playing music in a playlist doesn’t make songs loop by default; it’s only due to the nature of music listening that music apps include a loop option).

The problem still stands though: Control Center does need some attention, and of the existing solutions, I too think the shrink-panes-to-reveal-other-panes solution is the best.

In Uncategorized by Mayur Dhaka