Researchers have observed that fatigue – caused by brainwork or sports overtraining, for example – causes people to pick simpler, faster options.ksuklein/iStockPhoto / Getty Images
Olav Krigolson knows what it’s like to have a tired brain – here and on Mars. Just before the pandemic, the neuroscientist from the University of Victoria and a team of researchers lived for a week in the Mars simulation habitat in Hawaii. They observed “what happens if you do 16-hour workdays, and what happens to decisions.” Not surprisingly, “decision making breaks down, slowly but surely.”
For instance, preparing dinner took extra thought, compared with breakfast. “We used to play a lot of euchre at night,” Krigolson says, and the cards they played weren’t always the best.
Antonius Wiehler has a similar problem. “When I’m tired, I start to snack unhealthily,” he says, and he is particularly attracted to sweets. However, the expert in cognitive neuroscience – working in France at Le Groupe Hospitalier Universitaire Paris psychiatrie & neurosciences – knows that he shouldn’t get mad at his lack of willpower. Rather, the glutamate in his lateral prefrontal cortex is at least partly to blame.
The side effects of thinking too hard
To discover how brain fatigue affects decisions, Wiehler and a team of researchers brought participants into the Motivation, Brain and Behavior Lab at the Paris Brain Institute, Pitié-Salpetrière Hospital. Over six hours, some of the people did difficult activities on a computer, while others did easier ones. Every so often, they were asked to select one of two alternatives, along the lines of, “Would you like us to give you €35 right after the experiment, or would you like to wait two months and we’ll give you €50?”
Earlier in the day, the answers generally leaned toward waiting for the bigger reward. As the hours wore on, however, the folks in the “difficult” group found the quick gain increasingly attractive, while the “easy” people clung to the one that was more substantial, but later. These results replicate previous findings, which have observed that fatigue – caused by brainwork or sports overtraining, for example – causes people to pick simpler, faster options.
The team also used magnetic resonance spectroscopy to measure the biochemical changes in participants’ brains as they did their various activities. The participants who did the difficult duty had much more glutamate in the lateral prefrontal cortex than those who did the easier one – an important neurotransmitter that helps messages get relayed between nerve cells (neurons) in the brain. But using so much glutamate to focus on the computer requirements meant that they didn’t have much to drawn on when the time came to pick between the alternatives, such as the €35 or €50.
Krigolson doesn’t find these results surprising. “It’s kind of like an adrenaline rush,” he says. “When you go to do something, you’re going to pull all of this resource towards where you need it.” Therefore, if your glutamate is busy helping you do an intellectual chore, you won’t have the amount required to give proper thought to an unrelated choice. “The less neurons that are up to the task, the less effective you will be.”
Wiehler is excited by the results, as finding a measurable cause is “fantastic.” Now comes the work of studying how this can aid people who suffer from cognitive fatigue – not just to keep them out of the cookie jar or to win card games, but to help in higher-stakes situations such as burnout or working in air-traffic control. “We can think of many applications.”
Seven ways to help your brain relax and refresh
By the end of a long day applying for grants, Kallee Lins found herself nailing the required questions, but getting a little too creative when it came to the extra details. “They sounded good at the time,” says the arts-organization administrator, based out of Nelson, B.C. But after looking at them later with a fresh mind, she bemoaned, “What was I thinking?”
Many of us also find ourselves making poor decisions at the end of a hard day. We snap at our kids when we should remain calm. We guzzle a soft drink instead of water. We click “purchase” for those shoes we know we can’t afford. So, what can we do to rest and rejuvenate our heads?
1. Leave it till morning
“The practical life advice is that important choices should be done in the morning – or, maybe, if you’re rested, after lunch,” Wiehler says.
Krigolson agrees, explaining that there are two ways we make decisions: system one, which relies on gut hunches, and system two, in which we really think it through. “As we get tired, we move into this gut-hunch system,” he says. Therefore, morning-time choices are better thought-out; even people who consider themselves night owls probably form wiser judgments earlier in the day.
2. Take minibreaks throughout the day
As Wiehler comments, rest is good, too. The ideal length isn’t known, but he states that his study participants’ two short breaks clearly weren’t enough. “This 10 minutes didn’t help. So how long the break needs to be – it’s somewhere between 10 minutes and a night of sleep.”
Could a nap fit the bill? Maybe, but Wiehler says they don’t know. Krigolson also suggests a brief walk, getting fresh air or drinking some water. “There are lots of ways to try to recharge.”
3. Get a full night’s sleep
Not only does a night’s sleep push our decision making until morning, but it may improve off-balance glutamate levels. Although not yet scientifically proven, Wiehler says that “sleep should restore this.”
It’s also essential for brain and body health in general. “Most human beings need between seven and nine hours a night. You can’t get around that,” Krigolson says. “The gold standard for whether you’re in a good mental state is to be able to wake up at the same time every day, without an alarm clock, and without needing a cup of coffee to get going.”
4. Down that mocha – but know it’s temporary
“Yes,” Krigolson admits, “caffeine gives you a small boost in brain function, but it’s for about 15 minutes, maybe 30.” If you’re exhausted, it may be a good idea, “but you’re far better off to go into that situation where you don’t need that cup of coffee because – guess what! – you’re rested.”
5. Don’t buy into nutritional hype. Just eat healthy food
While “there’s no such thing as a superfood” when it comes to boosting your brain’s resources, Krigolson says, a well-rounded diet is the ticket. “The best thing out there is the new Canada food guide. They nailed it pretty much perfectly.”
6. Add some me-time to every day
Our schedules aren’t always optimal when it comes to making choices – especially when we’re trying to cram everything in after a couple of years of doing little because of the pandemic. Krigolson says, “We’re out the door fast, we’re not eating breakfast, we don’t have time to exercise, we’re probably tired from whatever happened the day before, and then we’re sitting there trying to make decisions.”
Make sure to allow for free time, too. Even good-for-you activities like exercise don’t always have to be all-out. “Thirty minutes of walking every day is all you need.”
7. Exercise your brain but don’t make it a chore
To keep your brain fresh, “keep your mind active,” suggests Marc Poulin, an Alzheimer’s researcher and professor of physiology at the University of Calgary. Plus, “Be socially engaged.”
At the same time, don’t stress about always keeping your brain busy with activities like Wordle or Sudoku. Calm and creativity are great brain-boosters, too – whatever way you find your bliss. Get out into nature, bake a cake or sit down for meditation or breathwork.