Thursday, November 03, 2005

Providing instructions for simple applications

The "Three Designing Women" in their book Interaction Design enumerate six usability evalution principles: effectiveness, efficiency, utilit, safety, learnability and memorability. I've been reflecting on the learnability of a simple application such as Apple's Photo Booth application that I described playing with about two blog entries ago. For an experienced user like me, Photo Booth was easy to pick up. I mapped my prior knowledge of Apple (and Windows) applications and was off pretty quickly. I do remember puzzling about settings and I found out how to do that with a little bit of experimentation.

Photo Booth does not come with trainer wheels. The operational procedure for this simple application is not immediately obvious to the inexperienced computer user. I estimate that it will take no more than a minute, and perhaps even just half a minute, for an experienced person to train a user how to operate the application. Further, once you learn to use it, it is not difficult to remember its operational procedure.

In a case like this, an application designer is faced with the following design choices: should one provide operational instructions on the screen, or should those be avoided altogether and either have the user learn by exploration or be taught to use it by a trainer? The answer to this question is not straightforward, so a discussion is warranted. As I thought about the issue, it became clear that the context of use plays a critical role in determining the answer. Consider a couple of scenarios:

Scenario 1: Photo Booth is installed in an unmanned kiosk that is visited by one-time users. Typically, such users are in a hurry, especially if there is a line of users waiting behind them. On-screen instructions would save users a lot of time and help them focus on their goal.

Scenario 2: Photo Booth is used in a home often by its residents. While on-screen instructions would help the first time, they would increasingly appear annoying after a while, and make the screen appear busy. Further, since there might be more than one person at home, there is most likely someone to help out a novice.

The choice then is to either not provide any instructions, on the assumption that this is an easily learned, easily remembered application, or provide instructions that can be banished forever when desired. Many risk-averse users, however, tend to play it safe by not removing instructions even when they are no longer needed. Also, a vendor may wish to project a perception of ease of use (zero-length learning curve), and providing on-screen instructions may take away from such a marketing goal. One could also point to other devices that one uses like bicycles and refrigerators that are at least as complex but don't carry instructions on the body of the machine itself -- the presence of such instructions may appear foolish after a while (of course, one can always peel off the sticker).

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