Cognitive test battery
sleepiness, PVT
POSITIVE
The cognitive test battery consisted of two tasks and two questionnaires and was administered in the following order: Karolinska Sleepiness Scale (KSS) [In the KSS, participants rated their level of self-reported sleepiness on a 9-point Likert scale (1—very alert, 9—very sleepy, and great effort to keep awake). The 2-min DSST was used as a measure of the speed of processing. In this task, participants were required to match symbols to digits as quickly as possible following a key shown on screen. The total number of correct trials was used as the critical measure. On the PANAS, participants responded to 20 adjectives describing positive and negative mood states on a 5-point Likert scale (1—very slightly, 5—extremely). Positive and negative affect scores are represented by the sum of the item responses. We also examined the “Alertness” and “Attentiveness” ratings on the PANAS. Finally, the 3-min PVT assessed levels of vigilance. At intervals varying randomly from 2000 ms to 10 000 ms, a counter on the screen appeared and participants were to press a key as quickly as possible. Lapses were defined as responses exceeding 500 ms.