The way you sleep may reveal aspects of your personality, with dark traits such as narcissism and cheating linked to night owls.
A study by researchers in Sydney and Liverpool has found the "dark triad" of personality traits - narcissism, psychopathy and Machiavellianism - are linked to those who prefer to stay up late.
Dr Peter Jonason of the University of Western Sydney said the study of 263 people found those who employed "cheater strategies" were more likely to do so under cover of night.
"Those who embodied darker aspects of those personality traits had an evening disposition, meaning they're more likely to have optimum cognitive functioning, optimum metabolic functioning later in the day, as opposed to people who are low on those traits." He said those traits might be associated with night owls because night was the best time to avoid being detected in "cheater" activities - which he described as breaking the rules, trying to get something for nothing, and beating the system.
"Someone who repeatedly doesn't pay for their train fare, or tries to get out of things that we as a collective think you should do."
Other research has shown more positive traits associated with night owls, including being extroverted, outgoing, creative and inventive.
Morning larks have been found to be agreeable, conscientious, analytical, logical, and to do better in school, according to studies reported in the Daily Mail.
Dr Alex Bartle of the Sleep Well Clinics said he wasn't aware of particular personality types associated with sleep cycles, other than research showing night owls were more likely to suffer depression, while early risers were more likely to be anxious.
According to Dr Bartle, chronotypes, or sleep patterns, are genetic, so night owls can train themselves to get up early if necessary, but will always revert to their genetic type.
"Because they have a genetic tendency to be evening people, as soon as they sleep in at weekends, then on Monday morning they're going to struggle."
Light is a key factor in resetting your body clock, so getting outside during the day helps keep your sleep patterns on track.
Dr Bartle said about 30 per cent of people were evening chronotypes, and about 15 per cent morning ones, with the rest somewhere in the middle.
India Lopez has been a lifelong lark. The 26-year-old magazine subeditor never has a lie-in.
"I set my alarm for 6.30 but I never sleep till then," she said. "The second I wake up, my mind is instantly active and I want to spring out of bed straight away and start working through my list of things to do."
Ms Lopez says she wakes early no matter how late she goes to bed, and can't remember ever being a late riser, even as a teenager.
She's sometimes self-conscious that early risers are seen as less relaxed, but she identifies strongly with some of the personality traits associated with larks. "I'm an introverted, list-maker, goal-ticker type."
For 20-year-old Henry Mene, mornings are a challenge. He sets six alarms on his mobile phone, but sometimes the battery runs out before he wakes. "My phone dies because the song has been playing over and over for more than an hour and I'm still sleeping," he said.
"I have to leave it on the charger just so the phone can keep going until I wake up."
His natural pattern would be staying awake until between 1am and 3am, and sleeping to about 10am. But having to get up for work at 8.30am means he often gets by on just four or five hours of sleep.
While he doesn't fit the dark triad of personality traits, Mr Mene said he was extroverted, which has been associated with night owls.