Responsiveness

The responsiveness of an interactive system describes how quickly it responds to user input.

Long delays can be a major cause of user frustration, or let the user believe the system is broken, or that a command or input gesture has been ignored. Responsiveness is therefore considered an important issue for human-computer-interaction (HCI).

Responsiveness is not the same as performance. A system with a good performance can have a poor responsiveness, and vice versa.

How much delay is too much?

The frustration threshold can be quite different, depending on the situation. The three "magic numbers" are 0.1s, 1s, and 10s.

See also
* http://www.useit.com/papers/responsetime.html
* http://performance.netbeans.org/responsiveness/whatisresponsiveness.html
* http://developer.gnome.org/projects/gup/hig/2.0/diff-from-1.0/feedback-response-times.html

Solutions

Usually, the best and most common "medicines" to responsiveness issues are
* a decent process management system, giving highest priority to operations that would otherwise interrupt the user's work flow, such as typing, onscreen buttons, or moving the mouse pointer. Usually there is enough "idle time" in between, for the other operations.
* Using idle time to prepare for the operations a user might do next.
* Let the user do something productive while the system is busy - for instance, writing information in a form, reading a manual, etc. For instance, in a tabbed browser, the user can read one page while loading another. Ideally, the
* Deliver intermediate results, before the operation is finished. For instance, a web page can already be operated before all images are loaded.
* If some waiting is inevitable, a progress indicator can significantly reduce frustration. For short delays, an animated icon might be sufficient, longer delays are better covered with a progress bar.
* Provide a control to stop the process and try something else.

See
* http://www.baychi.org/calendar/20031111/

See also

Responsivity, a related concept in electrical engineering.

Reactivity, an unrelated concept in chemistry.

External links

* [http://developer.kde.org/documentation/books/kde-2.0-development/ch09.html] Chapter 9. Constructing A Responsive User Interface. by David Sweet