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Hot Weather Really Does Turn People Into Jerks

Don't take it personally.
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Summer: a time for beach trips, patio drinks, and August vacations. Also summer: a time of year when everyone is a bit more of a jerk.

Since the 1970s, social psychologists have studied the many correlations between heat and hostility. People honk their car horns more when it's hot; major league baseball pitchers get more aggressive; college students who've been slighted by a "negative evaluation" are more tempted to give their evaluator an electric shock.


On perhaps a subtler level than electric shocks, hot temperatures may also make us less helpful to others. The findings come from research published in the European Journal of Social Psychology, by co-authors Liuba Belkin, an associate professor of management at Lehigh University, and Maryam Kouchaki, an assistant professor of management at Northwestern. The researchers, who both have backgrounds in organizational psychology, conducted a three-part study to research the effects of ambient temperature on "prosocial" behaviors—that is, instances of helping others that don't come with a reward.

In part one of the study, Belkin and Kouchaki compared archival data from a large Moscow retail chain for travel and leather goods. The data came from undercover shoppers hired by the company to observe and report on customer service. In 2010, the region faced what Science magazine called a "mega-heatwave," breaking a 500-year record for heat in Europe, with temperatures exceeding 100 degrees Fahrenheit—made worse by Moscow's then-lacking infrastructure for central air conditioning. To compare, 2011 was a typical summer for Moscow, with average temperatures around 73 degrees.

When the researchers compared the secret shoppers' reports from 2010 and 2011, they found the mega-heatwave really did make a difference: when it was uncomfortably hot, sales associates were 50 percent less likely to help customers. Those helping behaviors included things like greeting customers, volunteering to help, actively listening, and providing suggestions on merchandise. But Belkin and Kouchaki didn't know where the drop in helpful behavior was coming from—was it heat-induced fatigue, an increase in negative feelings, a drop in positive feelings, or some hellish combination of all three?


In their second study, the authors tried to tease out an answer. They conducted an experiment online with 160 paid participants, and divided them into two groups: they asked half of the participants to "recall a time when they felt uncomfortably hot" (with help from pictures of people suffering from heat), and the other half to recall the events of the previous day. In the meantime, participants answered easy trivia questions, and filled out questionnaires about their perceived levels of fatigue and positive and negative feelings. At the end of the study, participants received a request from the researchers to complete an additional brief survey for a new project, for which they would not be paid extra.

By the end of the experiment, only 44 percent of participants in the heat condition chose to help with the additional survey, compared to 76 percent in the control group. Those in the heat group also reported higher levels of fatigue and a decrease in "positive feelings"—which contributed to the drop in prosocial, survey-completing behavior in the heat group, according to the authors.

To test their hypothesis more directly, the authors conducted a third experiment with two groups of undergraduates at a US university, who were taking the same management course with the same professor, but were in different "sections" taught on the same day. The instructor taught one section in in a hot classroom (80 degrees) and one in an air-conditioned room (69 degrees). After covering the day's lesson, the professor asked both sections to complete an optional survey for a non-profit organization that helps underprivileged kids in their community with their remaining classroom time. They were allowed to answer as many questions as they liked—from one to the total of 150.

By this point, the results shouldn't be surprising: students in the hot classroom were less likely to stick around to fill out the survey (36 percent left class without responding to any questions, compared to just 5 percent of students in the cool classroom). Among those who did stay, students in the hot classroom filled out an average of 6 questions, compared to 35 in the cool classroom. Students who reported feeling more fatigued also tended to answer fewer questions.

In their conclusion, Belkin and Kouchaki used the "conservation of resources" theory to explain their findings: heat makes people feel tired, a state of resource depletion. With fewer "resources," people have fewer positive feelings, which are considered our inspiration for prosocial behavior. In other words, when you're feeling sweaty and gross, you lack the spring in your step to go out of your way and help other people.

"The point of our study is that ambient temperature affects individual states that shape emotional and behavioral reactions," Belkin told Quartz. "So people help less in an uncomfortable environment, whatever the reason they come up with to justify why they cannot do [it]." If your fellow citizens are ruder than usual on a really hot day, try not to take it personally.

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