8.1.1 Visibility

Recall that a key usability design feature identified by Donald Norman – from his analysis of using everyday objects such as doors – was visibility. An everyday object such as a door, or a control such as a button on a product should appear to be obvious about how it is used, and indeed it should perform that obvious function. For example, is it obvious how you insert a disc into a player? Is it obvious how you switch the machine on, adjust volume, and so on?