Designing Web Interfaces

Part VI. React Immediately

The previous two principles introduced the power of invitations and the usefulness of Transitions. Invitations are powerful because they directly address discoverability and provide feedback before an interaction happens. Transitions are useful because they provide visual feedback during an interaction. But another class of feedback exists. It is the feedback that happens immediately after each interaction with the system—an immediate reaction paired with the user’s action.

Newton’s Third Law of Motion states:

For every action, there is an equal and opposite reaction.

This law explains how a bird flies. Its wings push air downward. At the same time the air pushes the bird upward. The amount of force downward on the air equals the amount of upward force from the air. For every action there is an equal and opposite reaction. These are often called action-reaction force pairs.

While we can’t literally extend Newton’s law to the world of user interfaces, we certainly can apply this principle to the way we should interact with users. When users click on a button, they expect the button to depress. When they type in a field, they expect to see characters show up in the text box. When they make a mistake, they want the application to tell them where they goofed. When they start to search, they would like the results to show up as they type. When they start an unknown process, they hope they will be guided step by step with clear, timely, and contextual feedback. ...