In extreme heat, we often find it difficult to concentrate, our productivity decreases, and we become more irritable. Hot weather puts increased stress on the body as a whole, but how exactly does elevated temperature affect our brain and central nervous system? Let’s see what science has to say about this.
In July 2016, Boston (USA, Massachusetts) experienced unusually hot weather — the average daytime temperature did not drop below 93 degrees for almost a week. Some local students were lucky to live in dorms with central air conditioning. Others were not so lucky — the old student dorms did not have air conditioning systems.
Scientists from Harvard University, led by Jose Guillermo Cedeño Laurent, decided to take advantage of this situation to assess how heat (and especially high nighttime temperatures) affected the mental abilities of students [1].
Cedeno invited 44 students (24 of whom lived in dorms with air conditioning, 20 without) to participate in an experiment in which they had to solve math problems and take self-control tests. The testing was repeated several times: five days before the heat wave began, every day during the hot weather, and two days after the heat finally subsided.
“Many people are convinced that hot weather does not affect their well-being. We decided to check whether this is really true,” says Cedeno.
It turned out that even young and healthy students had lower mental performance in hot weather. On the hottest days, students who lived in dormitories without air conditioning (in these buildings, the temperature did not drop below 26 degrees even at night) showed significantly worse results in control tests than students who were lucky enough to live in buildings with air conditioning (in them, the temperature at night was much more comfortable – about 21 degrees).
It is well known that prolonged hot weather poses significant health risks – increasing the risk of heat stroke, heart attacks and sudden death, especially for the elderly and those with chronic illnesses. But elevated temperatures also affect our brains, making it difficult for us to think clearly and making us more irritable, impulsive and aggressive.
Why can hot weather reduce mental performance?
Jose Cedeno’s findings are supported by other studies, most of which were conducted in labs. When the temperature in the lab rose above comfortable levels, subjects’ performance on thinking tests worsened.
In one study [2], raising the room temperature by just 4 degrees (from 24 to 28 degrees) resulted in subjects’ performance on tests of memory, reaction time, self-control and planning deteriorating by 10%.
This effect can have serious consequences for students, for example. American economist Jisung Park studied [3] the results of tests and exams in high schools and found that students’ scores were lower when exams were held in hotter weather (on average, at temperatures above 22 degrees, grades were lower by about 0.4% for each additional degree of temperature).
In another study [4], Chi Sung Park also found that the more hot days there were during the school year, the worse students’ performance on the final exam – with grades particularly affected by days when thermometer readings exceeded 27 degrees.
he scientist believes that the reason is precisely that in such weather, students, on average, learn material worse.
Interestingly, this effect was stronger in schools in poorer areas, which often lacked air conditioning.
Why can heat make us aggressive?
Studying crime statistics, researchers found that on average, hot days see more violent crimes – murders, beatings, domestic violence. Other manifestations of aggression also increase – for example, on such days, Internet users leave more offensive comments, and drivers use their horns more often.
For example, in one of them, subjects playing a computer game behaved more aggressively towards other players if the temperature in the room was higher.
Especially in hot weather, so-called reactive aggression increases. This means that we more often perceive the words and actions of other people as aggressive and offensive and react with counter-aggression ourselves.
“The increase in reactive aggression in hot weather is likely due to the fact that the areas of our brain responsible for self-control are less efficient in such conditions. As a result, we are more likely to act impulsively and rashly, and it is more difficult for us to restrain ourselves,” explains research psychologist Kimberly Meidenbauer.
What happens to our brain in hot weather?
Scientists have not yet been able to determine exactly how heat affects our thinking and emotions, but there are several theories.
One of them is that in hot weather, the brain’s resources are spent on maintaining an optimal temperature, leaving less energy for everything else. “When the air temperature rises, blood flow increases in the areas of the brain responsible for thermoregulation, and they also receive more nutritious glucose. The areas of the brain responsible for higher mental functions may not have enough resources in such a situation,” explains Kimberly Meidenbauer.
“In addition to thermoregulation, the brain creates an acute feeling of discomfort when it overheats, which should prompt us to urgently find a way to somehow cool the body. Of course, discomfort from heat itself contributes to decreased performance and increased irritability,” explains neurosurgeon Shaun Morrison. Heat can also prevent us from getting a good night’s sleep, which in itself has a negative effect on our performance.