Figure 4.

Subjective sleepiness across hours of the day. Visual analogue scale (VAS)-measured subjective sleepiness averaged across protocol days for No Nap (black circles) and Nap (white circles) groups, respectively. (A) Sleepiness plotted for each time of day as differences from baseline, as in Figures 2 and 3A. Vertical lines indicate timing of afternoon nap. (B) Sleepiness collapsed into three segments, as in Figure 3B, reported as marginal means from mixed-effects analyses reported in the manuscript. Error bars indicate standard error of mean (SEM). *p < .05.