Post-nap nighttime polysomnographic sleep variables for Short and Long conditions at (a) mid and (b) end laboratory sessions. Sleep stage percentages, including wakefulness after sleep onset, are expressed as a percentage of the interval from sleep onset to wakeup time, or sleep period time (SPT). The duration of nighttime SPT varied among subjects but did not differ between Short and Long groups. A mixed MANOVA (Condition × Session, including all sleep stage percentage variables), n.s. No main effects for Condition or Session, and no interaction effects.