Part 6: 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.

In short, users want the application to react to their every action. The interface should React Immediately.

While there is a possibility of too much feedback (or, more accurately, too much of the wrong feedback—a concept we will discuss in the upcoming chapters), a system with little or no feedback feels sluggish and thickheaded. Immediate reactions are an expected part of intelligence. You can't have an intelligent interface without them.

Wundrbar.com is an example of an interface that reacts immediately (Figure P6-23). Wundrbar provides a search layer to a number of third-party services such as purchasing flight tickets, renting cars, or checking gas prices. As the user types a flight search in an input field, the interface formats a flight search form in real time. The tight loop between input and immediate feedback makes it easy to create a correct search (Figure P6-23).

Figure P6-23. As the user types in a flight search, Wundrbar immediately displays what it understands; the user is able to express all the needed input

It should be noted that while interfaces built in this style have only recently shown up on the Web, this principle is not new to the world of user interfaces. The Mac OSX Human Interface Guidelines calls this principle "Feedback and Communication," and describes its goal as:

...keeping users informed about what's happening by providing appropriate feedback. When a user initiates an action, always provide an indication that your application has received the user's input and is operating on it.^[47]

^[47] http://developer.apple.com/documentation/UserExperience/Conceptual/AppleHIGuidelines/XHIGHIDesign/chapter_5_section_2.html

Jakob Nielsen, in his widely recognized heuristics research, described a principle of "visibility of system status" in which:

...the system should always keep users informed about what is going on, through appropriate feedback within reasonable time.^[48]

^[48] http://www.useit.com/papers/heuristic/heuristic_list.html

Bruce Tognazzini, founder of the Human Interface Group at Apple, captured the essence of this in his design principle called Latency Reduction,^[49] in which the user is kept engaged throughout a lengthy process. The emphasis is on communication, feedback, and engagement.

^[49] http://www.asktog.com/basics/firstPrinciples.html#latencyReduction

The next two chapters will look at two areas where we can directly apply this principle:

Chapter 13

Discusses Auto Complete, Live Suggest, Live Search, and Refining Search.

Chapter 14

Covers Live Preview, Progressive Disclosure, Progress Indication, and Periodic Refresh.