A team of researchers has developed a new model to better explain why violent crime rates are consistently higher near the equator compared to other parts of the world.

The new model, called CLASH (CLimate Aggression, and Self-control in Humans), moves well beyond the simple fact that heat is linked to aggressive behavior. It suggests that a hot climate combined with less variation in seasonal temperatures can lead to a faster life strategy, less focus on the future, and less self-control, all of which contribute to aggression and violence.

The new model is described in an online article in the journal Behavioral and Brain Sciences.

“If there is less variation, you’re freer to do what you want now, because you’re not preparing foods or chopping firewood or making winter clothes to get you through the winter. You also may be more concerned with the immediate stress that comes along with parasites and other risks of hot climates, such as venomous animals,” said lead author Dr. Paul van Lange, a professor of psychology at the Vrije Universiteit Amsterdam (VU).

People living in these climates are oriented to the present rather than the future and tend to have a faster life strategy — they do things now. This can lead people to react more quickly with aggression and sometimes violence.

“We see evidence of a faster life strategy in hotter climates with less temperature variation — they are less strict about time, they have less use of birth control, they have children earlier and more often,” said Dr. Brad Bushman, co-author of the study and professor of communication and psychology at Ohio State University.

Although many previous studies have shown that levels of violence and aggression are higher in hot climates, the two leading explanatory models — the General Aggression Model and the Routine Activity Theory — aren’t quite satisfactory, said Bushman.

The General Aggression Model (which Bushman helped develop) suggests that hot temperatures make people uncomfortable and irritated, which makes them more aggressive. “But that doesn’t explain more extreme acts, such as murder,” Bushman said.

The Routine Activity Theory suggests that since people are outdoors and interacting more with others in warm weather, they naturally run into more opportunities for conflict. But this still doesn’t explain why there’s more violence when the temperature is 95 degrees F than when it is 75 degrees F, even though people might be outside under both circumstances.

It is believed that the CLASH model offers a more solid explanation regarding the impact of climate on rates of violence in different parts of the world, said van Lange.

“Strong seasonal variation in temperature affects culture in powerful ways. Planning in agriculture, hoarding, or simply preparing for cold winters shapes the culture in many ways, often with people not even noticing it. But it does shape how much a culture values time and self-control,” said van Lange.

The theory is not deterministic and isn’t meant to suggest that people in hotter, consistent climates can’t help themselves when it comes to violence and aggression.

“How people approach life is a part of culture and culture is strongly affected by climate,” said Van Lange. “Climate doesn’t make a person, but it is one part of what influences each of us. We believe it shapes the culture in important ways.”

Since CLASH is a new theory, more research is needed to confirm its validity. But Bushman said a lot of evidence already suggests that the theory may be on to something.

“We believe CLASH can help account for differences in aggression and violence both within and between countries around the world,” he said. “We think it provides a strong framework for understanding the violence differences we see around the world.”

Source: Ohio State University



Image Credit: Robert A. Rohde.

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