We’re all aware that eight hours of sleep is the golden number to be at your most productive, but sometimes a proper night of shut-eye just isn’t in the cards. For the standup sleepers who get a full eight, bravo, you win at life. For those who average closer to six, you’re in trouble. According to a recent sleep deprivation study, subjects who were allowed only six hours of sleep per night for two weeks eventually functioned just as poorly as those who were forced to stay awake for two days straight. And while the groups who slept anywhere from zero to four hours per night showed the lowest functionality and cognitive performance, the six-hour group was actually unaware of just how sleep deprived they were, showing a continued decrease in cognitive performance as the study went on and rating their sleepiness level as being not all that bad. Yikes! What this means is that people often don’t realize how sleep deprived they actually may be, leading to a consistently subpar level of daily functionality. So the next time you catch yourself yawning mid-afternoon, you’ll know why—and that the fix is eight solid hours of rest.