4. Designing an interface

The HCI designer can take advantage of people's mental model of how interfaces should work. This allows the interface to be predictable and therefore easy to use.

Have a look at this unusual interface.

It is not immediately obvious how this works. You can probably guess that the figure can be rotated in some way, but what do the UI dots in the lower left do? You will have to follow instructions or you will simply try things out and learn as you go along.

This does not mean that this is a poor interface, in fact it makes sense once you understand what it is trying to do - But - you had no mental model already in place and so you had to work much harder.

Now compare it to this familiar interface of a web browser

It does not really matter what web page you are viewing, you instantly understand how this interface is likely to behave. You have a mental model in place from your experience with similar interfaces.