In “fast-paced situations with uncertain outcomes and imperfect information,” good decision-making is “significantly hampered” by sleep deprivation, according to a new study by researchers from Washington State University and the University of Melbourne, Australia.
Police officers, soldiers, disaster management personnel, and other emergency responders whose lives–and the lives of others–may depend on their ability to quickly recognize and adapt to changing circumstances may suffer “catastrophic effects” because sleep loss blunts their reaction to feedback regarding the situation they’re in, the researchers report.
“Although this theoretical study examines rather extreme sleep deprivation, the findings send an important cautionary message to law enforcement,” says Dr. Bill Lewinski, executive director of the Force Science Institute. “This study adds important weight to the evidence that fatigue can have a profound effect on an officer’s performance and needs to be addressed on both a departmental and personal level.” (The Institute was not involved in the new experiments.)
SLEEPLESS IN SPOKANE
At WSU’s Sleep and Performance Research Center in Spokane, WA, researchers led by Dr. Paul Whitney, a psychology professor and associate dean, randomly divided 26 healthy, drug-free volunteers, 22 to 40 years old, into two groups.
Both groups initially spent two restful days and nights in the laboratory, with 10 hours in bed each night. Then one group was kept continuously awake for 62 hours (2 1/2 days), followed by two “recovery” days with 10 hours in bed each day. The control subjects continued their normal sleep pattern throughout this period.
At 48-hour intervals, all participants were subjected to various “decision tasks” to measure their cognitive capability.
The core testing component involved “go/no go” decision-making. A series of two-digit numbers was repeatedly flashed before the participants for three-quarters of a second each in random sequence. Four of the numbers represented “go” or “hit” signals, another four “no go” or “false alarms.” But the volunteers were not told which were which. They had to figure this out through trial and error. Their “accuracy feedback” was coupled with fictitious money rewards and losses to underscore that risks underlay their decisions.
After each volunteer had several dozen trials to learn the go/no go sets, the meaning of the numbers was reversed without warning or announcement. The subjects then had 40 trials to determine and master the new “response sets,” based on outcome feedback from their decisions.
This experiment, conducted on three occasions with different numbers, “captured three key elements of decisions” made in real-world circumstances, Whitney writes. The choices were forced “under time pressure; [the] choices produced good or bad outcomes; and feedback from outcomes [had to] be used to guide future choices.”
Diminished ability to use feedback to shape decisions became “especially prominent” when the sudden, unpredictable need for “reversal learning” was introduced, the researchers discovered.
Before sleep deprivation was imposed on the one group and “all subjects were well rested,” both groups “performed equivalently,” the researchers report. They were gradually able to determine the initial go/no go pattern and with reasonable practice overcome the “immediate and substantial disruption” of the sudden reversal.
After sleep deprivation kicked in, however, “striking differences in performance emerged,” the study found.
Even before the reversal point, the sleepless volunteers were “less effective” at figuring out the proper response pattern. After the reversal, their decision-making failed alarmingly.
While the rested group detected the new pattern within eight to 16 tries and “quickly returned to its previous high level of performance,” the sleep-deprived subjects “showed a profound inability to differentiate” the new numerical associations, even across 40 trials. Indeed, their average score of proper responses was “reduced to near zero” after the change of circumstances and showed no improvement going forward.
Even after recovery sleep, “significant differences” persisted with the sleep-deprived group, reflecting marked “decreases in hits and increases in false alarms” compared to the control group. Separate tests of concentration (“sustained attention”) also revealed notable deficits among the sleep-deprived, the researchers report.
Sleep loss appears “particularly problematic for decision making involving uncertainty and unexpected change,” the researchers conclude, with “blunted reactions to feedback” seeming to underlie the failure to adapt to “changing contingencies.”
“The results reveal that no matter how hard a sleep-deprived person tried to make the right decision, sleeplessness created short-circuits in the brain that prevented them from making the right choice,” Psychology Today reported.
Lewinski told Force Science News: “There’s a failure in processing information and subsequently formulating judgment that appears to come with fatigue. You just can’t get your brain to think about things correctly.”
Whitney’s team is convinced that something more than a compromised ability to focus attention is involved. But the researchers are not certain what that mystery factor might be.
Still, “our findings tell us that putting sleep-deprived people in perilous environments is an inherently risky business,” says Dr. Hans Van Dongen, director of the sleep center and a member of the research team.
The study does not reveal at what point sleep deprivation begins to affect decision-making. But Lewinski points out that other research has shown that being awake even for 18-20 hours can produce cognitive impairment equivalent to a DUI-threshold level of intoxication.
“In a threatening situation outside of a laboratory, you may get an adrenalin jolt that will temporarily off-set fatigue and facilitate better performance,” Lewinski says. “But that surge lasts only a very short period of time, you have to be aware of the threat for the adrenalin even to be released, and it never brings you to the same cognitive state where you’d be if you were fully rested.
“Fatigue is a critical issue for the safety of officers and those they are sworn to protect. Departments need to be conscious of fatigue in scheduling shifts, and officers need to be mindful as well in accepting overtime and planning their off-duty hours.”
The 12-page Washington study, titled “Feedback Blunting: Total Sleep Deprivation Impairs Decision Making that Requires Updating Based on Feedback,” appears in the journal Sleep. It can be accessed free of charge by CLICKING HERE.
Our thanks to Force Science Certification Course graduate Robert Bragg Jr., manager of fitness, force, and firearms training for the Washington State Criminal Justice Training Commission, for alerting us to this research.