How heat affects the brain

In July 2016, Boston was hit by a heat wave that saw daytime temperatures average 92 degrees for five consecutive days. Some local college students staying in Boston over the summer were lucky enough to live in dorms with central air conditioning. Others, however, were not. They were stuck in old dorms without air conditioning.

José Guillermo Cedeño Laurent, then a researcher at Harvard University, took advantage of this natural experiment to show that heat, especially nighttime heat, can Affected the cognitive abilities of young peopleHe had 44 students take math and self-control tests five days before the temperature rise, every day during the heatwave, and then two days after the heatwave.

“A lot of us think we're immune to heat,” says Dr. Cedeño, now an assistant professor of environmental and occupational health and justice at Rutgers University, “so what I wanted to test was whether that's actually true.”

It turns out that even young, healthy college students are affected by high temperatures: On the hottest days, students in unair-conditioned dorms where the average overnight temperature was 79 degrees Fahrenheit performed significantly worse on tests they took each morning than their air-conditioned counterparts, whose rooms were kept at a comfortable 71 degrees.

Another heat wave is coming Northeast, South, MidwestHigh temperatures can cause alarming situations Physical effectsIncreased risk of heart attack, heat stroke and death, especially senior citizen and, Chronic illnessBut heat also puts a strain on our brains, impairing our cognitive performance and making us irritable, impulsive and aggressive.

Why heat makes us stupid

Numerous laboratory studies have found similar results to Dr. Cedeño's, finding that cognitive test scores drop when scientists increase the temperature inside a room. 1 study They found that an increase of just 4 degrees (which participants said was still comfortable) was associated with an average 10% decrease in performance across tests of memory, reaction time and executive function.

This could have real consequences. R. Jisung Park, an environmental and labor economist at the University of Pennsylvania, said: High school standardized test scores They found that for every degree above 72 degrees Fahrenheit, body temperature drops by 0.2 percent. That may not seem like much, but it makes a big difference to students taking exams in 90-degree heat in rooms without air conditioning.

in Another studyPark found that the more hotter-than-average days there are during the school year, the worse students perform on standardized tests, especially when temperatures exceed 80 degrees. He believes this is because longer exposure to heat affects students' learning throughout the year.

The effect was “more pronounced among lower-income and racial minority students,” Dr Park said, possibly because they are less likely to have air conditioning at school or at home.

Why heat makes us aggressive

Researchers first discovered the link between heat and aggression in Crime DataHot days have been found to increase homicides, assaults, and domestic violence, and this relationship also applies to non-violent acts: As temperatures rise, people are more likely to commit violent acts. Hate speech online and Honking the horn in a traffic jam.

Laboratory studies back this up. 2019 ExperimentPeople behaved more maliciously towards others while playing the specially designed game. Video game A hot room is better than a cool room.

So-called reactive aggression tends to be particularly sensitive to heat, possibly because on hot days people are more likely to interpret the behavior of others as more hostile and respond in kind.

Kimberly Meydenbauer, an assistant professor of psychology at Washington State University, believes this increase in reactive aggression may have something to do with the effects of heat specifically on cognitive performance. Decreased self-control“The tendency to act without thinking and the inability to stop certain behaviors also appears to be affected by heat,” she says.

What's happening in the brain?

Researchers aren't sure why heat affects our cognition and emotions, but they have some theories.

For one, it diverts brain resources from thermoregulation, leaving less energy for other things: “If you're allocating all your blood and glucose to the parts of your brain involved in thermoregulation, it's very likely that you won't have enough energy for these higher cognitive functions,” says Dr. Meydenbauer.

Heat and discomfort might be making you feel distracted or irritated, but it's actually part of your brain's coping response. If you can't cool down, your brain “will make you feel even more uncomfortable and will focus all its energy on finding what you need to survive,” explains Shawn Morrison, M.D., professor of neurosurgery at Oregon Health & Science University.

Thermal effects sleep Temperature may also play a role: A Boston study found that hotter temperatures disrupted students' sleep and led to worse test scores.

The best way to counter these effects is calm downIf you can't use air conditioning, a fan can help. And don't forget to stay hydrated. It may sound obvious, but what matters most for your brain, mood, and cognition is how hot your body is, not the temperature outside.