Are you a night owl? You already know from previous studies that you are less likely to be a CEO than your early-rising colleagues, emphasising a perception that rising late is associated with being a indolent, ill-disciplined sluggard.
Now an Anglo-Australian research project has shown that those who sleep in and then stay up late tend to display more narcissistic, manipulative and psychopathic tendencies.
The lead researcher, Dr Peter Jonason of the University of Western Sydney, postulated that there might have been an evolutionary advantage for the distinction, based on an adaptation to the low-light environment late at night for antisocial activities.
What is not clear is whether this finding has any relevance to this region, where the well-known fondness for late nights is more a reaction to the climate than to any other factor. In the West, people sleep earlier.
And night owls can take comfort in the findings of a Belgian study that showed that they have more mental stamina and think more freely.
And which group would you rather be in: President Obama, Winston Churchill and Marcel Proust - night owls all - or George W Bush, Thomas Edison and Napoleon, who were always up with the dawn?