Heat makes people aggressive – these are the reasons

The train stops in Lübeck – and everyone wants to get on the next overcrowded RE train with their beach bags to travel from Hamburg to the sea on one of the last late summer days with around 30 degrees Celsius. But an argument between two women interrupts the excited activity. “Don’t push me,” calls a lady with glasses in a patterned shirt to a young woman in flared trousers and 90s sunglasses who is hurrying past.

And before she knows it, the young woman gets a resounding slap in the face. The rest of the passengers are dismayed. A man from DB security checks to see if everything is OK, and the women part ways, cursing, without any further outbursts of violence. And on the way to the Bay of Lübeck I am left wondering whether the heat is not just literally going to people’s heads.

It quickly becomes clear that the phenomenon has a name: “Long Hot Summer Effect”. It describes the fact that people behave more aggressively and are more easily irritated at high temperatures. The scientists Paul A. Bell and Robert A. Baron first investigated the phenomenon of heat and aggression in the 1970s. They divided 64 male students into two groups. One group was allowed to criticize the other. The other was allowed to punish them with electric shocks. And: the hotter it was in the test room, the more often the students gave their critics electric shocks.

Heat and aggression

The influence of heat on behavior is wide-ranging: from temperatures to penalties in professional football (National Football League in the USA) showed that the hotter it was, the more players violated the rules. The home team in particular tended to behave aggressively. The researchers therefore assume that in addition to the heat, the fans present could also play a role. The heat also seems to have an effect on drivers in traffic: in the research staff, the green traffic light was “overlooked”. On hot days, this caused the waiting drivers to become particularly dissatisfied: it ended in particularly extensive honking. Those who did not have air conditioning in their cars honked the most.

In addition to these rather harmless consequences, heat also seems to have more drastic effects: studies from the USA over a period of 45 years found that violent attacks increase in warm years and seasons. On the other hand, researchers found that people are less helpful in high temperatures. US scientist Craig Anderson showed more than 20 years ago that more violent and sexual crimes are committed during heat waves. A study from 2021 even found that on very hot days, violence among prisoners in prisons increases by 18 percent.

However, due to their design, the results of such experiments and studies can only ever be interpreted as an indication of a connection. They cannot therefore prove that the increased aggressiveness in hot weather is actually due to this. The researchers cannot rule out that other factors, such as more people spending time outdoors or more alcohol consumption, also play a role.

Comfortable temperature for Central Europeans: 22 to 25 degrees Celsius

One thing is certain: heat has a direct effect on our bodies. In addition to the obvious fact that the body increases sweat production when it is hot so that the body temperature does not get too high, the blood vessels also expand. This lowers blood pressure. The heart reacts to this by increasing its pumping capacity. Heat can therefore act as a stressor for us.

For Central Europeans, the comfortable temperature is around 22 to 25 degrees Celsius, Professor Hanns-Christian Gunga told the . He set up the Center for Space Medicine and Extreme Environments at the Charité in Berlin. If the thermometer climbs to 30 degrees and more, this is too much for Central Europeans. One possible explanation for aggressive behavior in hot weather is the hormone vasopressin, which regulates water balance and is released in greater quantities by the body at high temperatures. This is because the body tries to store as much fluid as possible and therefore releases more of the hormone. But this not only affects water balance, the hormone also increases our tendency to be aggressive.

Heat can make us feel unwell

There could be a very simple explanation for why the warm weather drives us crazy: we quickly become irritated when we feel unwell. Among other things, this can be due to: increased sweating, poor sleep, tiredness and

He suspects that when the weather is stressful, people tend to misunderstand ambiguous situations, which can lead to more misunderstandings and conflicts.

High temperatures can have a negative impact on mental health

In addition to aggression, heat can also lead to more . “During a heat wave, there is a significant increase in stress, anxiety and depression, especially among older and weakened people, but also among younger people who are not very fit. The prospect of not being able to escape this heat leads to psychological problems that should not be underestimated,” explains Hans-Peter Hutter, environmental physician at the Medical University of Vienna in . This can lead to panic attacks, among other things.

from the USA and Mexico even comes to the conclusion that the risk of suicide is increased on hot days.