Memory encoding
During the encoding phase, there was no significant difference between conditions in terms of accuracy of judgment (i.e. whether a specific feature was present, “yes” or “no,” mean accuracy >0.91, Mean (SD) for picture judgment accuracy and response times as well as memory performance measured by AʹRetrieval performance (Aʹ) on the picture encoding task for the wake, 10 min, 30 min, and 60 min nap conditions. Diamonds with error bars represent the means and +/− standard error. **At retrieval, there was a significant effect of nap condition for A’ (Furthermore, we examined if sleep inertia may have contributed to the effect of nap duration on memory performance. As we observed significant sleep inertia on the DSST median RT measure (see the section below for details), we included this measure as covariate in the model. The main effect of nap condition remained significant, suggesting that differences in sleep inertia incurred after waking did not account for the superior memory performance in the 30 min nap.No significant associations were observed between sleep parameters and memory retrieval performance for the 30 min nap condition (