Anecdotally, we know we make worse decisions when we’re tired than after a good night’s sleep. Now, a new study published in the Journal of Neuroscience puts a finer point on the link between sleep deprivation and unwise decision-making, finding that a sleepy brain tends to make overly optimistic gambles.
Any casino owner probably could have told you that. The study found that when asked to make money-based decisions after pulling an all-nighter, people tended to try to maximize their winnings instead of defending against potential losses. Further, brain scans showed that activity increased in the reward-related regions that assess positive outcomes in the sleepy brain, while those that process judgment of negative outcomes declined. (More on Time.com: Do You Love Your Stuff Too Much? Maybe It’s Because No One Loves You)
That helps explain why casinos keep gamblers awake all night, plying you with free booze, bombarding you with bright lights and offering no windows to the outside world. “Late-night gamblers are fighting more than just the unfavorable odds of gambling machines; they are fighting a sleep-deprived brain’s tendency to implicitly seek gains while discounting the impact of potential losses,” said Vinod Venkatraman, lead author and a psychology graduate student at Duke University, in a statement.
Until now, scientists had thought that sleep deprivation impacted decision-making by hobbling the brain’s memory and ability to focus attention. The current study, the authors say, is the first to show that sleeplessness also affects economic behavior and the brain’s assessment of monetary gains and losses — and perhaps other types of valuation — independent of attention.
The researchers asked 29 healthy adults, average age 22, to complete a series of gambling tasks at two separate times: first at 8 a.m. after a full night’s sleep, then again a week later at 6 a.m. after a night of sleep deprivation. The researchers used functional MRI scans to measure brain activity while the participants were gambling and also when they were asked to witness the outcomes of some of their decisions. In addition, the participants completed tests of vigilant attention. (More on Time.com: Young Adults Choose Self-Esteem Boost Over Sex and Money)
The authors write:
While well-rested participants sought to minimize the effect of the worst loss, sleep deprivation caused the same individuals to be less concerned about losses and to shift to a strategy that improved the magnitude of the best gain. … Sleep deprivation appears to create an optimism bias; for example, participants behave as if positive consequences are more likely (or more valuable) and as if negative consequences are less likely (or less harmful).
“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,” co-author Dr. Michael Chee, professor at the neurobehavioral disorders program at Duke-NUS in Singapore, said in a statement, noting also that studies show that after long stretches of on-call wakefulness, medical students tend to make more mistakes.
So could an extra cup of coffee help bring restore your judgment? “Stimulants may improve vigilance but their influence on other aspects of cognition, such as decision making, is less clear,” the authors write. Which is just another reason to turn off the lights, switch off the cell phone, close the laptop and get a solid night’s sleep.