The Psychomotor Vigilance Test

The psychomotor vigilance test (PVT) is a tool used to measure a person’s behavioural alertness. It is a visual test which involves measuring the speed at which a person reacts to visual stimuli (e.g. a red dot against a black background).

The standard PVT is ten minutes in duration.1 Five minute and three minute PVTs are also available. The PVT is becoming an increasingly valuable tool in the sleep field as it is a very good measure of behavioural alertness in relation to sleep loss/deprivation or circadian rhythm misalignment. 

David F. Dinges, an American Sleep research and professor of Psychology developed the PVT.5 The standard ten- minute PVT measures response times to the visual stimuli, which are presented to the subject on a device such as a laptop, at random times during the ten-minutes. Lapses in attention measured by the PVT can occur as a result of lack of sleep and/or prolonged hours on the job.  Sleep loss has been shown to impact the reaction times measured by the PVT by lengthening reaction time values and increasing the number of lapses and false starts (i.e. responding in anticipation of the stimulus).

Parameters measured by the PVT include lapses of attention and impulsivity (false starts) and well as mean, median and standard deviation response times. Slowest and fastest reaction time percentage values can also be determined. The parameters measured as well as the definitions of these parameters may differ depending on the specific PVT software and hardware used.

An advantage of the PVT is that it is not very time-consuming and it requires no training. It only involves a brief explanation of the procedure to the subject prior to the start of the test. It has the ability to be utilised in a number of fields e.g. in determining behavioural alertness in commercial drivers, pilots and heavy-machinery operators.2 A five minute reaction self-test has been undertaken by NASA astronauts while in space, as well as for land missions and training exercises, in order to measure their alertness as a result of sleep loss or circadian rhythm misalignment.4 The PVT gives a more objective measure of alertness compared to tools like Epworth Sleepiness Scale (ESS) which relies on the patient giving a subjective measure of their sleepiness/alertness.  

A limitation of the PVT is that certain patients (e.g. colour-blind, patients with cognitive impairment, patients with physical impairments like Parkinson’s disease) would not be suitable as the outcomes of the PVT would be influenced by their physical/mental limitations.  The results of the PVT may also vary depending on the PVT software and hardware used. Another limitation, particularly of the ten-minute PVT, is that in certain clinical/operational settings, the test may be considered too long and therefore impractical. Some of the shorter PVT versions however may lose their sensitivity compared to the standard PVT as they may be considered too short to detect a significant deterioration in alertness.1

There are several PVT apps and software available, some of which are free to access e.g. PEBLTM and CorwareTM. Other cognitive tests are available for purchase e.g. Joggle ResearchTM (for AppleTM devices).3

PVT testing

 

Research into the use of the PVT in sleep has been undertaken over the past years and it ongoing e.g. developing an adaptive version of the standard ten minute PVT for use in measuring alertness in sleep restricted subjects.1 It is proving to be a resourceful tool in objectively measuring behavioural alertness in patients referred for sleep-related issues.

By Conchita Rego

Princess Alexandra Hospital

References

1.      Basner M, Dinges DF, An Adaptive-Duration Version of the PVT Accurately Tracks Changes in Psychmotor Vigilance Induced by Sleep Restriction, Sleep 2012; 35 (2): 193-202

2.      Basner M, Dinges DF, Maximizing Sensitivity of the Psychomotor Vigilance Test (PVT) to Sleep Loss, Sleep 2011; 34 (5): 581-591

3.      Pulsar Informatics Inc, Quickly & Easily Measure the Effects of Fatigue; 2013 [Accessed 08/11/2014]. Available from: http://buypvt.com/

4.      Victor M Escobedo Jr, NASA, Psychomotor Vigilance Self Test on the International Space Station (Reaction Self Test),; 2014 [Accessed 08/11/2014]. Available from: http://www.nasa.gov/mission_pages/station/research/experiments/982.html

5.  University of Pennysylvania, David F. Dinges, Ph.D. Director, Unit for Experimental Psychiatry; 2008 (Accessed 08/11/2014), Available from: http://web.archive.org/web/20071114225121/http://www.med.upenn.edu/uep/dinges.shtml