This should explain why your wife or girlfriend always wants to wake up early on Saturday to do brunch and take on the day when all you want to do is keep sleeping.

A study at Brigham and Women’s Hospital in Massachusetts found that the average woman’s internal clock runs about six minutes faster than the average man’s.  A six-minute difference doesn’t seem like much, but the researchers found it makes a huge difference.

Women are much more likely to identify themselves as “morning people”, have an easier time getting out of bed and have more trouble staying up late when they’re tired.  It also leads to more insomnia in women.  The researchers say that if you are a woman who has trouble with insomnia or constant fatigue, one strategy is getting shades that make your bedroom go completely dark.

Your internal clock is tuned to need darkness earlier so by blocking out all of the light, it makes it easier for you to go to sleep.