Science Confirms That Summer Heat Makes Us Grumpy

Feeling especially resentful toward your boss today? Before firing off that passive-aggressive email, get up and check the nearest thermostat. Scientists writing in the European Journal of Social Psychology say being in the heat makes people crankier, less cooperative, and less likely to help others.

Researchers Liuba Y. Belkin and Maryam Kouchaki, from Lehigh University and Northwestern University’s Kellogg School of Management respectively, conducted three experiments to test the effects of heat-related discomfort on human emotions and behavior.

For the first part, the researchers pulled data from a summer 2010 study conducted in Russian shopping malls. (Bear with us—this will make sense.) The original study had collected data from secret shoppers visiting a popular chain of handbag and luggage stores. As with any secret shoppers, the study participants’ job was to record and report their experience with the store and its staff. It would have been an ordinary gig—except that many of the stores were stiflingly hot. Moscow was experiencing a "mega-heatwave" that summer, and many malls lacked air conditioning.

Store employees really seemed to be feeling the heat. The data showed that they were 59 percent less likely that summer to ask customers if they needed help, make suggestions, volunteer assistance, or show signs of active listening. They just couldn’t be bothered. Interestingly, they weren't entirely slacking off; for instance, the stores were as clean as they always had been. The mall workers just had trouble with the human relations part of the job.

In the second experiment, the researchers recruited 160 participants to take an online trivia quiz. Before starting the quiz, half the participants were instructed to imagine themselves in an uncomfortably warm setting. Then they answered a few questions about their feelings, and then they took the quiz. After that, they were asked if they’d be willing to complete a short survey about their experience.

The trivia quiz was essentially a ruse; it was the post-quiz survey the researchers were after. More specifically, they wanted to see if anybody took the survey at all.

A lot of people did. But people who’d had to think about being hot were significantly less likely than others (44 percent versus 77 percent) to agree to do it. They also reported feeling more tired and less happy than everyone else.

The final experiment involved 73 of Belkin’s college students. She taught the same class on organizational management in two sessions—once in a stuffy room (80°F) and once in air conditioning. At the end of each session, each student was asked to complete a 100-question survey to support a nonprofit that helped underprivileged children.

You already know where this is going. Students in the hot room answered far fewer survey questions than those sitting comfortably in air conditioning (6 versus 35). Were they ditching the survey in order to could escape the room? It seems likely, Belkin told Quartz, "but whatever the reason, it affected their behavior."

"The point of our study is that ambient temperature affects individual states that shape emotional and behavioral reactions," she said, "so people help less in an uncomfortable environment, whatever the reason they come up with to justify why they cannot do" certain things.

Belkin says these findings carry over into the workplace, and warns employers to keep their employees, like zoo animals, at a safe and comfortable temperature. Sweat them long enough, she says, and they’ll quit. "We know that money matters," she said, "but only to a point."