According to Dr Peter Jonason from the University of Western Sydney and his colleagues, people who stay up late at night are more likely to display anti-social personality traits such as narcissism, psychopathy and Machiavellianism.

Of course, correlation is not causation.

“Those who scored highly on the Dark Triad traits are, like many other predators such as lions and scorpions, creatures of the night,” explained Dr Jonason, who reported the findings in the journal Personality and Individual Differences.

“For people pursuing a fast life strategy like that embodied by the Dark Triad traits, it’s better to occupy and exploit a lowlight environment where others are sleeping and have diminished cognitive functioning.”

last line here is key, from study summary...

AbstractIn this study (N = 263) we provide a basic test of a niche-specialization hypothesis of the Dark Triad (i.e., narcissism, psychopathy, and Machiavellianism). We propose that in order to best enact a “cheater strategy” those high on the Dark Triad traits should have optimal cognitive performance and, thus, have a night-time chronotype. Such a disposition will take advantage of the low light, the limited monitoring, and the lessened cognitive processing of morning-type people. The Dark Triad composite was correlated with an eveningness disposition. This link worked through links with the “darker” aspects of the Dark Triad (i.e., Machiavellianism, secondary psychopathy, and exploitive narcissism); correlations that were invariant across the sexes. While we replicated sex differences in the Dark Triad, we failed to replicate sex differences in chronotype, suggesting eveningness may not be a sexually selected trait as some have argued but is a trait under natural selective pressures to enable effective exploitations of conspecifics by both sexes.

KeywordsDark Triad;Narcissism;Psychopathy;Machiavellianism;Morningness:eveningness;Chronotype;Evolutionary psychologyFigures and tables from this article:

Table 1. Descriptive statistics and a summary of zero-order correlations and regression values for the Dark Triad (predictor variables) and chronotype (outcome variable).