Scientists use a technique known as psychomotor vigilance tasks or PVTs to understand the impact of sleep deprivation on human in studies. Simply put, it’s a reaction test: a red button randomly turns green and people have to push it as fast as possible. Not so surprisingly, those who get 8 hours of sleep over a 2-week period show very few lapses in attention and no cognitive declines. But those groups that receive either 6 or 4 hours of sleep see declining PVT results on almost a daily basis for the entire 2-week period. Of course the 4-hour group performs the worst. But these results don’t just show a loss of concentration, they show full lapses and awareness called “microsleeps”. In other words, their brains aren’t just slower but shutting off for moments at a time. When looking at the results deeper, scientists concluded that getting 6 hours of sleep for 10 days in a row was the same as not sleeping for 24 hours straight. That’s the same cognitive decline as being legally drunk. And if you get 4 hours of sleep for 11 days, it’s like you haven’t slept for 48 hours straight.