The expression ‘hot-headed’ might be more meteorology than metaphor.

The tendency of tempers flaring when the mercury rises is a long-documented fact, according to the Association for Psychological Studies. The same phenomenon applies behind the wheel of a car as well, researchers find.

In an experiment that might seem downright cruel, researchers Douglas Kenrick and Steven McFarlane purposely annoyed drivers by remaining stopped through a 12-second green light, and tracking the amount of time before drivers started honking.

The experiment took place in Arizona under temperatures ranging from 86 to 116 degrees Fahrenheit.

“As it got hotter, they wouldn’t wait as long to honk, and would lean on the horn longer,” Kenrick said in a telephone interview, adding the correlation was stronger in cars with windows open, indicating a lack of air conditioning. He also noted that young men were quickest to lean on their horns, particularly if there were other young men in the vehicle.

The work of another researcher, Craig Anderson, indicated that the increase of aggressive behaviors wasn’t limited to honking horns.

“Anderson found serious crimes like assault seem to go up during heatwaves,” Kenrick said.

Although heat tends to make people more irritable, and therefore more likely to lash out irrationally, there are things people can do to keep their cool.

It could be as simple as having a cool drink.

A 1976 experiment indicated that higher temperatures led test subjects to irrationally administer electric shots to others, however, a follow-up experiment indicated that a cool drink tamped down the ‘overt aggression’ displayed under hot conditions.

For those who find themselves succumbing to anger amid the stresses of traffic, the first 30 seconds are key.

“The thing about anger is, you have to keep paying attention to it,” Kenrick said. “You get more angry by keeping thinking about the (offense).” Something as simple as drinking cold water, turning on the radio, or other distractions can help break ‘that little loop’ of anger that could lead to destructive behavior if allowed to flare.

Kenrick said he feels road rage is an example of an ‘evolution and behavior mismatch.’ A confrontation might have served humans in past times, when people lived in smaller communities where everyone knew one another. But these days, most likely you will never see that jerk that cut you off in traffic.

His advice was to think of the offensive driver the way you would about a barking dog on the street – a dog you might simply cross the street to avoid.

“Thinking of them as angry dogs doesn’t annoy you as much as thinking of them as (rational) human beings,” he said.

“Thirty seconds later you’ll probably be over it,” he said.