High temperatures can make us miserable. Research shows they also make us aggressive, impulsive and dumb.
In July 2016, a heat wave hit Boston, with daytime temperatures averaging 92 degrees for five days in a row. Some local university students who were staying in town for the summer got lucky and were living in dorms with central air-conditioning. Other students, not so much — they were stuck in older dorms without A.C.
Jose Guillermo Cedeño Laurent, a Harvard researcher at the time, decided to take advantage of this natural experiment to see how heat, and especially heat at night, affected the young adults’ cognitive performance. He had 44 students perform math and self-control tests five days before the temperature rose, every day during the heat wave, and two days after.
“Many of us think that we are immune to heat,” said Dr. Cedeño, now an assistant professor of environmental and occupational health and justice at Rutgers University. “So something that I wanted to test was whether that was really true.”
It turns out even young, healthy college students are affected by high temperatures. During the hottest days, the students in the un-air-conditioned dorms, where nighttime temperatures averaged 79 degrees, performed significantly worse on the tests they took every morning than the students with A.C., whose rooms stayed a pleasant 71 degrees.
A heat wave is once again blanketing the Northeast, South and Midwest. High temperatures can have an alarming effect on our bodies, raising the risk for heart attacks, heat stroke and death, particularly among older adults and people with chronic diseases. But heat also takes a toll on our brains, impairing cognition and making us irritable, impulsive and aggressive.
How heat makes us dumb
Numerous studies in lab settings have produced similar results to Dr. Cedeño’s research, with scores on cognitive tests falling as scientists raised the temperature in the room. One investigation found that just a four-degree increase — which participants described as still feeling comfortable — led to a 10 percent average drop in performance across tests of memory, reaction time and executive functioning.