People who have not slept well are more likely to take bigger gambling risks than when they are fully rested, according to a study showing that sleep deprivation makes a person more reckless when it comes to the risk of losing money.
Most people are naturally cautious about taking a risk that could put them out of pocket, but this in-built fear of a "negative outcome" vanishes when people are deprived of a good night's sleep, something that has not been lost on all-night casinos, scientists said.
The study has implications for doctors and emergency services workers who may have to take life-threatening decisions at night, or when they have worked long hours without sleep or rest, said Professor Scott Huettel of Duke University Medical Centre in Durham, North Carolina.
A doctor who has to take a risky decision on a patient employs a similar judgement about likely positive or negative outcomes that someone makes when they take a gambling risk, yet if that doctor is sleep-deprived then he or she is more likely to think about the good outcome rather than the bad outcome, Professor Huettel said.
"Even if we give these people extra time at night to make a decision to try to compensate for them being tired, they are still more likely to put greater emphasis on the positive outcomes of their decision rather than the potential negative outcomes," Professor Huettel said. "This is the first time we've been able to show that we can relate sleep deprivation to a change in the way we tend to view things. One night's sleep deprivation is enough to change people's preferences when it comes to gambling on a likely outcome."
The study involved 29 young, healthy volunteers who were asked to stay up all night before undertaking a series of gambling tasks. Scientists also used a brain scanner to analyse the activity of their brain regions known to be involved in controlling positive and negative outcomes.
When rested, the volunteers showed a typically cautious pattern of behaviour when it came to gambling. But as they became more sleep-deprived, the behaviour switched to being less sensitive to potentially negative outcomes, with greater emphasis on the positive possibilities.
"We've shown that sleep deprivation is more likely to change how people value things. It may cause them to value something more, and other things less. Sleep deprivation surely makes gambling even more tempting to many people," Professor Huettel said.
Vinod Venkatraman, the lead author of the study, which is published in the Journal of Neuroscience, said: "Late-night gamblers are fighting more than just the unfavourable odds of gambling machines. They are fighting a sleep-deprived brain's tendency to implicitly seek gains while discounting the impact of potential losses."
Casinos and other gambling joints employ a range of psychological tricks to encourage gambling, from distracting lights and sounds to free alcohol and the abstraction of money into gambling chips or electronic credits.
Professor Michael Chee of Duke University said the findings have implications for professional financial advisers. "Even if someone makes very sound financial decisions after a normal night of sleep, there is no guarantee that this same person will not expose you to untoward risk if sleep deprived," Professor Chee said.
High achievers who couldn't sleep
The Victorian novelist's sleeplessness produced his essays, Night Life, which detail his walks through London's streets.
The French leader built an empire on less than four hours sleep a night, using the extra time to plan his next invasions.
The comedian developed insomnia after the stock market crash of 1929 in which he lost much of his fortune. He eased his symptoms by phoning strangers to shout insults at them.
Alexandre Dumas, père
The Count of Monte Cristo author might have sought help for his insomnia, but he also produced 1,200 volumes and claims to have fathered 500 children.
The 'Iron Lady' was famous for running the country on just four hours' of sleep a night, not sleeping at all during the three-month Falklands War, and having 20-minute cat-naps in the day.