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.

The scientists assessed 263 people’s tendency to be a morning- or evening-type person to discover whether this was linked to the so-called ‘Dark Triad’ of personality traits – Machiavellianism, narcissism and psychopathy. They found that participants who were awake in the twilight hours displayed greater anti-social tendencies than those who went to bed earlier.

“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.”

Dr Jonason said there may be an evolutionary basis for the link between anti-social behavior and a preference to being awake late at night.

“There is likely to be a co-evolutionary arms race between cheaters and those who wish to detect and punish them, and the Dark Triad traits may represent specialized adaptations to avoid detection.”

“The features of the night – a low-light environment where others are sleeping – may facilitate the casual sex, mate-poaching, and risk-taking the Dark Triad traits are linked to.”

“Indeed, most crimes and most sexual activity peak at night, suggesting just such a link.”

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Bibliographic information: Peter K. Jonason et al. 2013. Creatures of the night: Chronotypes and the Dark Triad traits. Personality and Individual Differences, vol. 55, no. 5, pp. 538–541; doi: 10.1016/j.paid.2013.05.001