Numerous studies have shown that lack of sleep hurts—it can lead to weight gain, diseases, and of course weakened cognitive functioning. But a bad night’s sleep doesn’t hurt everyone equally. Unlike me, some people can think clearly no matter what. A study published June 24th in The Journal of Neuroscience helps explain why.

Scientists looked for a genetic marker called Period 3 known to predict the effects of sleep deprivation. People with short versions of the gene do okay when they lose sleep. But the longer gene leads to suffering with lack of sleep.

Researchers tested attention and cognition before and after both good and bad nights’ sleeps. Those with the long Period 3 had poor function in the part of the brain that would usually spring to life. Even after a decent night, the long-gene people had reduced brain activity towards the end of the day. But folks with the short gene did better, and their brains even pulled in extra assistance from surrounding brain areas.