Vigilance
PVT
Improvements in objective measures of vigilance and speed of processing were less clear. While improvements in vigilance emerged half an hour after waking from the 10 min and 30 min naps, the 60 min nap did not show consistent benefits. As discussed, the less pronounced benefits to these domains compared to other studies may be related to participants keeping to their habitual short sleep schedule without deprivation beyond their usual amount of sleep. In support of this, none of the participants had more than two lapses or more than two false alarms for any of the PVT sessions, suggesting the presence of a ceiling effect. The 3-min PVT used here compared to the longer 10-min PVT may also have contributed to the decreased sensitivity of this task to nap effects under conditions of habitual sleep.