Perception of simulated driving performance after sleep restriction and caffeine.
OBJECTIVE
As feelings of alertness are reported to be highly correlated with performance perception, the objective of this study was to determine whether caffeine, a common countermeasure to driver sleepiness, affected a sleepy driver's ability to monitor his or her simulated driving performance.


METHODS
Twelve healthy young adults (six males, six females) participated in three counterbalanced, blinded, daytime conditions: control [9 h time in bed (TIB)], 100 mg caffeine (4 h TIB), and placebo (4 h TIB). Driving performance was measured through lane drift on a series of 30-min simulated driving sessions. Subjective sleepiness and perception of driving performance were measured at 5-min intervals during driving sessions via the Karolinska Sleepiness Scale and a corresponding perception scale.


RESULTS
Sleep restriction had a significant detrimental effect on driving performance and subjective measures. Caffeine resulted in significant improvements across all measures. Subjective measures were found to be significantly correlated after sleep restriction and prior to caffeine. Correlations between actual and perceived performance were nonsignificant across all conditions.


CONCLUSIONS
The strong correlation between subjective measures supports the postulation that sleepiness is used as a cue for performance prediction when sleep restricted. The relationship between perceived and actual performance after fatigue countermeasures remains inconclusive. Further research, addressing limitations, is needed.
Biggs
Sarah N
SN
School of Psychology, Centre for Sleep Research, University of South Australia, Adelaide, Australia. sarah.biggs@adelaide.edu.au
Smith
Andrew
A
Dorrian
Jill
J
Reid
Kathryn
K
Dawson
Drew
D
van den Heuvel
Cameron
C
Baulk
Stuart
S
D000328:Adult; D001334:Automobile Driving; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D010468:Perceptual Disorders / Q000209:etiology*; D012720:Severity of Illness Index; D012892:Sleep Deprivation / Q000150:complications* / Q000175:diagnosis; D012894:Sleep Stages; D014584:User-Computer Interface; D014796:Visual Perception / Q000502:physiology*
D000697:Central Nervous System Stimulants; D002110:Caffeine