Both social conditions lasted 12 hours (10 a.m. to 10 p.m.), and was followed by 22 hours of sleep deprivation, during which time participants were tested hourly for alertness and performance. Technicians monitored participants continuously to ensure that participants did not fall asleep. All told, participants remained awake for 36 consecutive hours.
During sleep deprivation, scores for speed on the Psychomotor Vigilance Test (PVT) deteriorated in all groups but was more pronounced in extroverts assigned to the socially enriched exposure compared with extroverts assigned to the socially impoverished condition at 4 a.m., 6 a.m., and noon.
The socially impoverished condition had minimal impact on test performance or subjective sleepiness in any of the groups.
"The ability of introverts to resist sleep loss, on the other hand, was relatively unaffected by the social environment," the authors noted.