[Lauren]

People probably don't have this. It seems relatively rare for us all to have.

The thing is, most of us stay up on our laptop til the early hours, or watch TV - and then claim we can't sleep. The light from the laptop and television affect the light pigment in our eyes and trick our brain into thinking it's daytime - so we don't feel sleepy. I'd bet loads of us, if we are active and physical throughout the day - then lay down at night in the dark - would sleep.