It’s so hot right now, I can’t even think of a hook for this article. And apparently, all the heat is to blame. Scientists have discovered that heat can—in fact—make you stupid. While it’s technically not as straightforward as all of that, heat does play a (potentially) negative role in the performance of the human brain. 

In 2018, researchers at the National Bureau of Economic Research (NBER) published a working paper on the effects of heat on the test scores of China’s gaokao or the National College Entrance Examination. 

From 2005 to 2011, they looked at the relationship between temperature and the scores of the students who took the test. They found that on hotter days, students would score lower in exams. 

According to the study, if the temperature increases by 3.29 degrees Celsius from the regular temperature in the area, students’ test scores drop by 1.12 percent on average. Chinese officials have even acknowledged that temperature plays a part in test scores, so they turn the air conditioning off in some regions in the spirit of fairness. 

In the United States, a similar study yielded similar results. 

A working paper by Jisung Park of University of California Los Angeles and Harvard University studied the standardized test scores of students in New York City from 1998 to 2011. The study found that the students taking an exam on a day where the temperature was 90 degrees Fahrenheit (or 32 degrees Celsius) reduced the performance of the student by 14 percent versus on days that the temperature was 72 degrees Fahrenheit (or 22 degrees Celsius). 

The study also found that when students take tests on hot days, students were 10.9 percent less likely to pass the classes they were taking, which meant that there was a 2.5 percent decrease in their likelihood of graduating on time. 

We deserve an explanation, an acceptable reason

The reason our brains perform on less optimal levels when exposed to high temperatures has a lot to do with what our brains are made of. A 2022 paper published in the Journal of Neural Engineering explores the link between neural activity and temperature changes. 

Dr. Steven Schiff, vice chair for global health in neurosurgery at Yale School of Medicine and one of the authors of the study, discovered that even a single degree Celsius change in temperature can affect the way neurons fire, and in turn, how the brain performs. 

The human brain gives off electric and magnetic signals, which is how the brain controls the rest of the body and regulates itself. When it gets too hot, the neurons that are in charge of firing those signals can go silent. But when these neurons return to a more acceptable temperature, they can resume firing. 

So yes, heat is the devil when you’re trying to do something important. 

While there are a few caveats in these studies (like how all of the subjects were students taking important tests), we can’t ignore how the brain works (or doesn’t work) in extreme temperatures. 

More than taking important tests on hot days though, the true problem lies in climate change. The earth’s temperatures are increasing at an alarming rate, which threatens the environment, people’s livelihoods, and potentially, how our brains function. 

But for now, at least we now have an excuse for that third iced coffee of the day.