As the name implies, hypovigilance is a state of diminished vigilance and attention, which reduces, among others, the abilities to direct attention and to perform multiple tasks at the same time. Hypovigilance is characterised by a decrease in sensory perception. Consequently, a higher level of sensory stimulation is required to get a person's attention. A sensation of muscular heaviness is also a sign of hypovigilance. However, both are usually not noticed by the hypovigilant person. Visible signs of reduced vigilance would include reduced movements and low muscular tension, which can be seen, for example, in the fact that the person's mouth is slightly open.

Hypovigilance can be usually expected in modern aeroplanes, especially during long flights where only monotonous tasks, which do not sufficiently stimulate the nervous system, are required of the pilot and periods without any events are experienced.