Humans are Generalization Machines
As human beings, without even realizing it, we are constantly creating generalizations as devices of cognitive efficiency.
For example, you probably know that this is a blog even though it’s content and design are completely unique. However, it has enough blog-like characteristics for you to stick it into the blog “bucket” in your brain. It lights up enough neurons that you have associated with blogs that you can say to some degree of certainty it is a blog.
As I said, this is a device for creating cognitive efficiency. Think about what it would be like if every time you saw a different make, model, and color of car, you would have to re-learn that what you were looking at was a car. You would never make it across the street.
Generalization allows us to see a tree, a pile of lumber, or a boat and think “wood”, which comes in handy when you need to find something to build a bonfire. It is a survival mechanism that is hard wired into our neurology. We know that big animals with sharp teeth are probably dangerous - even if we encounter a totally new animal.
Generalization is why one of the most important rules of web usability is also the title of one of my favorite books - Don’t Make Me Think. In general (huzzah!), novelty reduces usability. This is why so many computer and web UI controls mimic physical controls. A button looks like a button. Even the use of the word ‘button’ is a device to link machinery to something already familiar from clothing.
This is not to say that innovative controls don’t have their place. It’s just that you had better have a good reason for the novelty, and it should survive user tests.
Certainly the iPod control works very well for most people and it is a very new device control. However, it still relies on many standard user control paradigms. Fast forward is on the right and reverse is on the left. Sweeping your finger over the control surface behaves predictably like turning a knob or a jog-wheel. Pressing the big button in the middle selects a song (or whatever you are highlighting). These are not totally new ideas in user control. The brilliance of Apple is the combination of something new with things that people were already used to.
Through email I once debated the usefulness of top and side navigation bars with a user interface “guru” who publishes a lot and produces a lot of conferences. He argued that contextual, in-page navigation is much better and that top level navigation didn’t matter. Hogwash. That idea violates many tested web UI principles - generalization being one. You have a top level navigation because users expect to use it, and use it most often, even when contextual navigation is in place. I have been a part of many usability studies that have proven this out time and time again.
This is not meant to say that human experience design should be stale and unchanging. However, if you want people to use your web site or new device - you will not force them to spend a lot of time figuring out how to use it.
