This article originally appeared in TidBITS on 2011-01-07 at 2:45 p.m.
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User Interface Conservatism versus Liberalism

by Adam C. Engst

John Gruber, who puts a lot of thought into small things, has posted on Daring Fireball an excellent discussion [1] of user interface conservatism versus liberalism. He writes:

There’s a conservative/liberal sort of fork in UI design, in the sense of traditional/non-traditional. The conservatives see non-standard custom UI elements as wrong. Liberals see an app built using nothing other than standard system UI elements as boring, old-fashioned, stodgy.

This has been on my mind of late as well, and the highly liberal interfaces of the App Store application and the new Twitter application bring them to the forefront (Tim Morgan [2] pores over the details in his blog). What has happened to the Apple Computer of the past, with its vaunted Human Interface Guidelines?

[image link] [3]

Well, things have changed, as Gruber points out, and Apple itself has become a UI liberal over the history of Mac OS X. The Finder, iTunes, iPhoto, Safari—they’ve all served as UI experiments for Apple, although it’s hard to see the experiments being coordinated, given how different those applications are. The screenshot above is a joke, by the way. Apple does still publish Human Interface Guidelines for Mac OS X and for iOS [5]. The question is, are they being followed?

The problem with UI liberalism is not that it necessarily makes for bad interfaces. On the contrary, there are some very good interfaces that provide new and innovative ways of interacting with virtual tools. And the problem with UI liberalism is not even that it’s easier to create a bad interface, though that is certainly true, since a UI conservative can create a decent interface merely by slavishly following the rules and relying on standard controls.

No, the real problem with UI liberalism is that it reduces the usability of the platform as a whole. That’s of little concern to the individual developer, who just wants her app to stand out, but it is—or at least it should be—of concern to Apple, whose platform becomes harder to use with every app that reinvents the steering wheel.

To be fair, platform usability is less of a problem in iOS than it is in Mac OS X. Users interact with only a single app at a time, enabling mental models to swap with app switches. And the dictates of the small screens often override what would be ideal in a larger space—let’s hope that explains the hidden Search field in Apple’s iBooks app, which can be found only by being told about it or exploring the app like a video game. Plus, as I’ve said before, the magic of iOS devices is that they become the app that’s running, so it’s less disconcerting when each app’s interface looks radically different. And finally, because most iOS apps are quite simple and used for short durations, unusual interfaces don’t radically increase the learning curve or reduce productivity.

But on the Mac, platform usability is a big deal. To start, many of us use multiple applications simultaneously, viewing both on the same screen and switching back and forth with merely a click. Even more important is the fact that Mac applications work together—you expect to move data from one application to another seamlessly, whether by copy-and-paste or built-in mechanisms like Apple’s Data Detectors. The more you use applications in concert—and many of us spend our entire days at our Macs—the more you benefit from the consistent user interfaces designed by UI conservatives. And when applications rely on consistent user interfaces, they become easier to learn as well, which translates directly to the bottom line when we’re talking about productivity applications.

For better or worse, though, UI liberalism would seem to have the upper hand within Apple, with iOS developers, and, increasingly, with Mac developers. Apple’s full-screen interface for iPhoto ’11, for instance, may or may not be a good interface on its own, but it makes iPhoto ’11 harder to use for anyone who has experience with previous versions of the program, not the least because now there are two largely distinct interfaces for the program, each with its own pros and cons. And until Mac OS X Lion ships with Mission Control, switching from iPhoto ’11 in full-screen mode to another app causes iPhoto to drop out of full-screen mode, making it even more frustrating to move back and forth.

Who knew that Kai Krause, with his alien-inspired interfaces for Kai’s Power Tools [6], was merely a few decades ahead of his time?