People who stay up late are narcissistic, manipulative psychopaths.
Or at least they are on average. That's the conclusion of winners of the 2014 Ig Nobel Prize in psychology, Peter K. Jonason, Amy Jones and Minna Lyons, in their paper "Creatures of the night: Chronotypes and the Dark Triad traits", originally published in the September 2013 issue of Personality and Individual Differences.
http://www.sciencedirect.com/science/article/pii/S0191886913001918
The Ig Nobel Prizes are given by the scientific humor magazine The Annals of Improbable Research for science that first makes people laugh, and then makes them think. The 24th First Annual Ig Nobel Prize ceremony was held yesterday evening.
A full list of the winners, which included prizes in categories such as neuroscience (for a group of researchers trying to understand why people see the face of Jesus in toast) and biology (for a paper carefully documenting that dogs prefer to align themselves on a North-South axis when they shit), can be found at
http://www.improbable.com/ig/winners/