Vigilance, which is also known as sustained attention, is the ability to sustain attention during prolonged,
monotonous tasks. In a traditional laboratory-based vigilance task, the participant must maintain continuous alertness and watchfully wait to detect a signal stimuli that appears at an unknown time. Real-world vigilance tasks include watching a radar screen for occasional unexpected
blips, proofreading a text looking for spelling errors, remembering to check the speedometre at certain intervals to make sure we do not speed, etc.
Relevance for interaction design
A well-known usability principle states that designers should strive to put the user in control. The user, and not the system, should initiate and control actions. Vigilance tasks are however one area where it may be wise not to take the principle too literally. Humans are infamous for their poor performance on vigilance tasks, so it makes sense not to burden users with tasks such as reminding us of our appointments, auto-saving our word processor documents, etc.