We all know that one person who seemingly sails through life with hardly any sleep, looking as fresh as a daisy while you're propping your eyelids up with toothpicks.
But for those people who think they can skate through life skimping on sleep, researchers have news for you.
A study by the University of Utah has found that anything less than six hours of snoozing impairs your judgement and reasoning - even if you think you're fine.
“Most people feel terrible when they get less than six hours of sleep,” reveals study co-author Professor Paula Williams. “Although [short sleepers] report no daytime dysfunction from short sleep, what if their perceptions are inaccurate?"
Researchers looked at people who had a normal amount of sleep in the previous month, compared to those who had slept for six hours or less a night.
They then split the short sleepers into two groups: those who felt drowsy during the day, and those who claimed to feel fine.
When placed in an MRI scanner, it was found that both groups of short sleepers showed connectivity patterns more typical of sleep than wakefulness.
“We saw evidence that even among people who claim that they don’t have daytime drowsiness or effects of sleep deprivation, when you remove outside stimulation, they are stuck in [the MRI] and there is nothing to do," Paula told ABC News. "They may still lose wakefulness and perhaps very quickly."
One theory is that short sleepers who claim they’re fine have their wake-up brain systems constantly in overdrive, and might actually have a false perception of how awake they are.