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Yesterday, this newspaper looked briefly at the link between cold weather and violence. Today we take that analysis further to explain in a more technical manner why cold weather is such an important risk multiplier when food prices, transport costs, political anger, social media agitation, and incitement are already present.

Over recent weeks, The Common Sense has reported on how three factors have traditionally aligned in South Africa before outbreaks of mass violence. The first is the rising cost of food and transport. The second is incitement. The third is cold weather.

The answer to why that third factor is so important lies in the physiology of the brain.

When people are cold for a long time, especially when they are also hungry, tired, unemployed, under financial pressure, or living in poorly heated homes, the body enters a stress state.

The key part of the brain involved here is the prefrontal cortex. This is the area behind the forehead that helps people think before they act. It is the brain’s control room. It helps with planning, judgement, restraint, emotional control, and decision-making. When a person is calm, warm, and rested, the prefrontal cortex helps them absorb frustration without immediately lashing out.

Cold-induced stress weakens that control.

When the skin detects cold, signals travel rapidly to the brain. The body then begins protecting itself. Blood vessels tighten. Muscles may shiver. Heart rate and blood pressure may rise. Stress chemicals such as adrenaline and noradrenaline increase. If the stress continues, cortisol can rise too. These chemicals are useful for survival, but they also change how the brain works.

Under stress, the prefrontal cortex becomes less effective. It has less capacity to hold the bigger picture in mind. It becomes harder to weigh consequences, ignore provocation, or control anger. Research on stress and the prefrontal cortex shows that high levels of stress chemicals can impair the very brain circuits needed for working memory, self-control, and careful judgement.

At the same time, the amygdala becomes more important. The amygdala is the brain’s alarm system. It scans for threats, danger, and insults. Normally, the prefrontal cortex keeps the amygdala under control. It tells the emotional brain to calm down. It helps a person decide that a queue, a taxi fare increase, a rumour, or an argument is irritating, but not an immediate emergency.

Cold stress can weaken that brake. Cold stress reduces the connection between the amygdala and parts of the prefrontal cortex that usually help regulate emotion. That is the brain chemistry of irritability.

Put simply, the alarm system gets louder and the control room gets weaker.

Then incitement enters the picture.

Incitement works best when people are already primed for anger. It turns discomfort into blame and then uncontrollable anger. Cold weather therefore lowers the threshold at which existing social tensions explode.