Protocol. Each of the four groups received 9.0-hour nocturnal TIB for two nights prior to a 3-day manipulation period. These groups subsequently had: 9 hours nocturnal TIB (23:00–08:00), 6.5 hours nocturnal TIB (12:15–06:45), 5 hours nocturnal TIB (01:00–06:00) with a 1.5 hour TIB daytime nap opportunity (14:00–15:30), or 5 hours nocturnal TIB (01:00–06:00). On the second baseline day (B2), several measures from an evening test battery (KSS, N-back, and PVT) were analyzed to establish that groups did not differ prior to sleep manipulation. The Four Mountains Test took place at 16:45 on the third manipulation day (SR3), after the KSS, N-back, and PVT. Note that stated times on SR3 refer to the 6.5h and 5.0 + 1.5h groups (NFS4 study), while tests were consistently 30 minutes earlier for the 9.0h and 5.0h groups (NFS3 study). For the three manipulation nights, the 9.0h group could sleep from 23:00 to 08:00, the 6.5h group from 12:15 to 06:45, and the 5.0h group from 01:00 to 06:00. The 5.0 + 1.5h group were permitted the same nocturnal TIB as the 5.0h group (01:00–06:00), but had an additional 1.5 hour TIB during a mid-afternoon nap (14:00–15:30).