Have you given a warm handshake, an icy glance, or been in a heated argument? Temperature is often associated with human behaviors—in fact, it’s a phenomenon that persists across languages.
The concept is so embedded in our minds that physical temperature can affect our judgment and behavior, a growing body of research shows. One 2008 study found that subjects holding warm coffee were more likely to judge a target as warm and friendly than subjects holding iced coffee.
It all sounds innocuous until you consider that terms like “cold-blooded” and “hot-headed” refer to two very different descriptions of a similar crime: The slaying of another human.
Researchers in Switzerland and Germany set out to test if ambient temperature in a room could affect the way people judged crimes. “Words associated with coldness typically indicate that the person acted with forethought," they explain in a new paper. "Words associated with heat typically indicate that the person acted spontaneously and impulsively."
People in a cold room were twice as likely to describe a crime as murder than those in mid- and high-temperature rooms.
Those familiar with criminal sentencing (or Law & Order) know that the perceived intent behind a homicide has a large effect on the sentence. Pre-meditated killings tend be judged as murders and result in harsher sentences. Impulsive killings tend to result in lighter sentences.
The study, which was published this week in PLoS One, presented 133 subjects with photographs and descriptions of various crimes. They were randomly assigned to low-, mid-, or high-temperature conditions, with all conditions within an established building-code temperature comfort zone.
Participants were asked to answer “What kind of crime did this person commit?” in an open-response format. They also rated how likely the crime was impulsive and how likely it was premeditated. Two independent raters read the responses and determined prison sentences based on the language of the crime descriptions and “their lay understanding of German law." They also counted how many times the subjects described the crime as murder.
Those in the low-temperature condition were significantly more likely than subjects in the high-temperature condition to describe the crimes as premeditated and less likely to see the crimes as impulsive. They were more likely to refer to crimes as murders, and their descriptions of crimes tended to result in harsher penalties than subjects in high-temperature conditions.
Subjects in the mid-temperature condition did not significantly differ from high-temperature subjects in three out of four measurements, indicating that low temperature has a stronger effect on judgment than high temperature.
In fact, people in a cold room were twice as likely to describe a crime as murder than those in mid- and high-temperature rooms.
The researchers also measured other variables that might affect the results, including age, sex, outdoor temperature, and clothing—none of the factors correlated with the results.
It’s a chilling discovery, and researchers indicate the effect could extend to perceptions of witnesses on the stand or judges’ choices in the courtroom. If the results of this study are confirmed, perhaps 12 Angry Men would have been a shorter movie if someone had simply turned the thermostat up.