Changes to HSI hardware or software should not force users to have to unlearn existing skills. Additional Information: It is better for an upgrade to require the user to learn additional skills than to expect the user to change existing ones. Thus, changes in the information presented by the system
(e.g., messages, graphic symbols) are less difficult to adapt to if they do not require users to modify their skills or strategies. For example, changes limited to physical appearance do not typically seriously disrupt users’ performance, whereas changes in the operation of the system almost certainly will. However, sometimes the appearance of a system is strongly linked to user skills. For example, the layout of tools on the palette of a drawing program should not be changed in subsequent versions. Users who rely on spatial memory for retrieving tools from the palette will find that this skill leads them to select the wrong tool.6546