– Chrie

(This is admittedly a somewhat bad example because Safari and the Finder at least *show* you that one back button is active and the other isn’t, but it’s the first example that occured to me)

This is where consistency is important. Looks don’t really matter too much. It doesn’t matter whether your back button is a green arrow like in some versions of Firefox, or a black button with an arrow like in Safari and the Finder. What matters is that all back buttons behave the same so the user can get used to a behaviour, and trust that his actions always lead to the same reactions from the computer.

Creating a new theme for an application to reflect its metaphor is not going to trip users up. iTunes 7 is just ugly, not less usable as the user interaction is unchanged.

However there are issues with custom controls in terms of changing their behaviour (such as brushed metal window dragging) that can cause issues. I think I may post another entry rather than just a comment on that though so I can give it some thought.

Travis, thanks for your comments. I would argue that smart phones, VCR’s and blinking clocks are examples of poor user interaction design and not a lack of consistency.

The two stalk Ford is a good example for consistency. We used to have two cars at one point, each with two stalks but the controls were reversed. However with cruise control, telephone controls and radio controls being incorporated into the steering wheel show if we are too rigid we can stifle innovation. These changes make a compromise between consistency and proximity for the sake of improved safety. The look of those stalks varying from car to car is not an issue. Their relative layout can be an issue. The iPhoto search box being in the bottom right rather than top right can make you pause in your workflow. However absolute placement for specific controls within a window are not covered by the HIG.

The interface guidelines that Logic Pro follows are those from the music and audio studio, not the computer. You control Logic Pro with musical instruments and mixing controllers (banks of programmable knobs and sliders and buttons, transport controls, jog wheel, etc) not a mouse. The interface conventions of music and audio predate the personal computer entirely. I learned audio mixing in the 1970’s before I was 10 years old, it works the same in the current version of Logic Pro.

I regularly get tripped up by clever Flash(TM) designers who decide to redesign the scroll bar. For whatever reason, Flash makes it easy to design scroll bars that are NOT consistent in appearance. I for one find random triangle-like objects floating in vague proximity to possibly truncated text with no vertical throughline unintuitive. Yet these opaque every-Flash-app-makes-you-relearn-navigation approaches seem to proliferate…

Even the most basic metaphors have some idiomatic component. On the surface, my computer’s Trash Can is a metaphor for the trash can I have in my house. However, while rummaging through my real-world garbage to find the half-eaten tuna sandwich I threw out last week is generally discouraged, on my computer that’s the entire point. I can cut and paste pictures and news clippings in real life, but I can’t paste 25 copies without a trip to Kinkos.

These subtle differences are impossible to infer from the metaphor itself; they must be learned through experience and applied idiomatically. This is perfectly fine. Human beings are remarkably good at idiomatic thought, so good that most of the time, we take it for granted.

Idiomatic reasoning is deeply rooted in the principle of consistency. The last time I saw a long strip on the side of my screen with a rectangle and two arrows, I dragged it up and down to see different parts of my document. The next time I encounter a scroll bar, I’ll do the same thing. If scroll bars were not generally consistent in appearance and function, I would have a difficult time to

Now, you are absolutely correct that purely *visual* consistency is becoming less important, and Chris Ryland pinpoints the source of the change: the web.

Buttons on the internet look like all sorts of things, while still maintaining some consistent platonic quality of “buttonness”. Having been immunized by the mess of visual cues on the web, most users these days can spot that buttonness, even if the button doesn’t look 100% identical to the ones they encountered yesterday.

This doesn’t mean that *design* consistency is passé, just that appearances don’t need to be absolutely identical in order to maintain high levels of idiom recognition. Even though some Mac applications were Aqua, and some were Brushed Metal, they were designed pretty much the same way. Nobody panicked the first time they saw a brushed metal button and it didn’t look exactly like the aqua buttons they were used to. They clicked on it, it behaved exactly like the buttons they were used to, and they unconsciously filed away another data point for the next time they encounter an odd-shaped button.

The people still whining about visual consistency on the Mac are either treating outdated UI guidelines as though they were holy gospel, or they’re trying to hide their purely aesthetic complaints behind the usability banner to gain public support. To be honest, I don’t have much sympathy for them either way.