Alertness refers to the condition of general wakefulness that enables a person to respond quickly and appropriately to any given demand. It is the pre-requisite for effective behavior, and is in this respect the basis of every attention performance.
In this test, reaction time is examined under two conditions. The first condition concerns simple reaction time measurements, in which a cross appears on the monitor at randomly varying intervals and to which the subject should respond as quickly as possible by pressing a key. Intrinsic alertness is measured in this condition. In a second condition, reaction time is measured in response to a critical stimulus preceded by a cue stimulus presented as warning tone ("phasic arousal", or temporal orientation of attentional focus).