Easy to use vs Intuitive

This topic is a staple of UX. The basic idea is that there are two slightly different components to usability: the ability to discover the feature when attempting an unfamiliar task, and how easy it is to accomplish the task using the feature.

Sometimes one of the components suffers for a good reason. Nuclear launch interfaces are not easy to use, if movies are to be believed. There are keys, the little clear door covering the red button, launch codes, an interface requiring two people, etc. That’s the point. Intuitive use is most often sacrificed for speed, such as in the case of command line interfaces, copy edit notation, or code.

This gets more interesting when not looking at extreme examples, because that balance between ease of use, speed, and intuition is trickier to strike. Consider the uses of the home button on an iPhone:

1. Press while using phone: leaves application to the home screen
2. Press when phone is locked: activates screen and shows the slide to unlock element.
3. Hold (any state): voice control
4. Double press when phone is locked (but the screen is activated): shows ipod controls, double press again to hide controls
5. Double press when phone is awake:
   1. Phones that multitask show the task bar
   2. Previous versions allowed for customization allowing the user to set this action to open phone favorites (dearly missed by yours truly) or ipod controls.

Many people are not aware of #4 or 5.2, arguably because it is not something that people try with a button, making the action unintuitive (#3 also fails in this category as well). These features are shortcuts, so the 'speed over intuition' argument can be made.

It’s interesting to note that multitasking (#5.1) ‘took over’ an unintuitive feature. It was solved by.... training. Of course, Apple’s version of training was actually a demonstration by Steve Jobs himself, reinforced with at least one TV commercial, but it amounts to the same thing. One way to make the easy to use intuitive is to say “let me show you how great this is”.

This shows that in real life one has to make trade offs. The multitask home button action can be considered a shortcut, most people don’t use it often, and once the user learns it: it's fast and easy.