Table 1. Nocturnal sleep variables for the night before the experiments Variable measured (mean ± SD) Nap No-nap p Cohen’s d Total time in bed (min) 406.7 ± 71.9 415.2 ± 61.4 0.725 0.12 Total sleep time (min) 371.4 ± 75.0 379.8 ± 70.6 0.714 0.12 Latency to sleep onset (m) 24.7 ± 16.9 24.4 ± 16.3 0.958 0.02 Wake time after sleep onset (m) 35.6 ± 20.9 32.4 ± 17.6 0.591 0.15 Sleep efficiency (%) 91.0 ± 5.0 91.8 ± 4.9 0.591 0.17 No significant difference was observed in the measurement of nocturnal sleep on the day before the experiment.