Consistency and Perceived Stability

The principle of consistency supports users by allowing them to transfer their knowledge from one application to another (Apple Computer Macintosh Human Interface Guidelines 7; Microsoft 5). An application has to be consistent within itself, with earlier versions of the product, its use of metaphors, and also with the user's expectations (Apple Computer Macintosh Human Interface Guidelines 7-8). The latter is the most difficult kind of consistency due to individual differences (Apple Computer Macintosh Human Interface Guidelines 8, Microsoft 5; see also section 3.3.7).

 

Figure 3: A SimpleText Pull-Down Menu

The concept of perceived stability is closely related to the principle of consistency. Users are given a visual sense of stability, for example, [even] when particular actions are unavailable, they are not eliminated from a display but are merely dimmed (Apple Computer Macintosh Human Interface Guidelines 11; see Figure 3 for an example of a menu with dimmed actions). Both principles correspond to what has been said in section 3.2.2 and 3.2.3.