The time it takes for someone to respond to some sort of event, notification, alarm or cue. This may be affected by the form in which the event is presented (e.g. a loud sound vs a subtle change at the edge of the screen), and by the cognitive state of the user (e.g. waiting attentively or highly focused on another task). In the case when some sort of decision is also needed, then other issues will also be important, such as the number of choices and preparedness or implicit biases of the user.
