Vigilance (psychology)
[2] The study of vigilance has expanded since the 1940s mainly due to the increased interaction of people with machines for applications involving monitoring and detection of rare events and weak signals.
[citation needed] The systematic study of vigilance was initiated by Norman Mackworth during World War II.
[3] Mackworth's 1948 study investigated the tendency of radar and sonar operators to miss rare irregular event detections near the end of their watch.
Mackworth simulated rare irregular events on a radar display by having the test participants watch an unmarked clock face over a 2-hour period.
SDT assumes an active observer making perceptual judgments as conditions of uncertainty vary.
A decision maker can vary their response bias, characterized by Beta, to allow more or less correct detections (hits), but at the respective cost of more or less false alarms.
The degree to which the observer tolerates false alarms to achieve a higher rate of detection is termed the bias.
Mental workload, or cognitive load, based on task differences can significantly affect the degree of vigilance decrement.
In 1977, Parasuraman and Davies investigated the effect of two task difference variables on d', and proposed the existence of a vigilance taxonomy based on discrimination type and event rate.
Parasuraman and Davies employed discrimination tasks which were either successive or simultaneous, and presented both at high and low event rates.
[12][13] The effect of event rate on monitoring task performance can be affected by the addition of non-target salient objects at varying frequencies.
Clock test research conducted in the late 1950s and 1960s indicates that an increase in event rate for rare irregular low salience signals reduced the vigilance decrement.
Beginning in the late 1990s, neuroimaging techniques such as positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and Transcranial Doppler sonography (TCD) have been employed to independently assess brain activation and mental workload during vigilance experiments.
Studies employing PET, fMRI and TCD indicate a decline in activity in the prefrontal cortex correlates with vigilance decrement.
Neuroimaging studies also indicate that the control of vigilance may reside in the right cerebral hemisphere in a variety of brain regions.
These include the right frontal, inferior parietal, prefrontal, superior temporal cortices and cingulate gyrus.
[21] Activity in the LC noradrenergic system is associated with the alert waking state in animals through the release of noradrenaline.
Chemically blocking the release of noradrenaline induces drowsiness and lapses in attention associated with a vigilance decrement.
The role of the cingulate gyrus in vigilance is unclear, but its proximity and connections to the corpus callosum, which regulates interhemispheric activity, may be significant.
[32] Experiments involving both audio and visual stimuli indicate the expected training performance improvement within the first five to ten hours of practice or less.
In pilotage and airport security screening experiments, trained or expert subjects exhibit better detection of low salience targets, a reduction in false alarms, improved sensitivity, and a significantly reduced vigilance decrement.
[40] Berardi, Parasuraman and Haxby reported no differences in 2001 in the overall levels of vigilance and the ability to sustain attention over time for when comparing middle aged (over 40) and younger subjects.
More recent ERP studies indicate that when performance declines during a vigilance task, N100 amplitude was not diminished.
