Short winter days depress some individuals and bad weather gives most of us cabin fever. Yet, the weather has little to do with happiness overall. The well-known pattern of summertime riots may have little to do with heat-related irritability. Like everyone else, rioters just like to be outdoors on fine days.

The psychology of weather is as iffy as the forecast

We all complain about bad weather. Yet, the climate has little or nothing to do with how happy people are. Thirty years ago when Ireland was a poor country its residents were far happier than those of other poor countries. In fact they were as happy as Americans who were much richer then. Irish happiness defied dismal weather with perpetual cloudiness and drizzle.

So darkness doesn’t necessarily cause unhappiness. However bad the weather, people get used to it—a phenomenon that happiness researchers refer to as gravitating to a fixed happiness level (or set point) that is set by genes and childhood experiences.

So although some individuals are vulnerable, most people do not get depressed during the dark days of winter. What about the related claim that the heat of summer makes us irritable thereby contributing to violent crime and riots?

Heat and violence

There is a correlation between violent crime in American cities and average temperature (1). Hotter cities have more crime. In general this means that Southern cities are more violent. Does the heat make us southerners flip our lids and commit horrible acts of violence? Perhaps not. Criminal violence varies with family structure, ethnic group, and other factors that vary across cities and were not controlled by the researchers. In my own cross-country comparison, I also found that average temperature was unrelated to violent crime (2).

My impression is that there is far less substance to the heat-aggression claim than meets the eye. This is hardly surprising in view of the complex results produced by social psychologists who took this problem into the lab decades ago.

Turning on the heat—in the lab

When people are exposed to high temperatures in the lab, we respond much like a dog in midday sun. We become irritable. Yet, we are unwilling to put out unnecessary effort. Generally speaking heat does not increase aggression although it may well sap our intellectual energy and make us prone to following bad examples (3).

That finding likely encouraged researchers to investigate whether riots are more likely to occur on hot summer days. Interestingly, they found that there is a substantial increase in the probability of riots on hot days (4).

Summers of discontent?

This might seem like compelling evidence that heat causes aggression but only if one bought in to similar interpretations of the other correlations. Yet, skepticism is often rewarded in these matters.

After all, the decline in rioting on cold days is easy to explain in more mundane ways. The Wall Street protesters (the 99 percent) were determined to keep going during the winter but cold weather defeated them in the end. Even the Taliban avoid fighting during Afghanistan’s brutal winter.

So winter chills riots by chilling rioters. But why would the hottest days produce more mass violence on the streets? We do not really know. One of the more plausible explanations is that there are simply more people outdoors during the summer and therefore more material for agitators to work with.

The relevant research also covered periods when there were a lot of people living in stifling homes that lacked air conditioning. Many people went outside during the hottest days to seek shade and some even slept outdoors in parks. Perhaps we should stop blaming the weather for our rioting as well as our moods.

To paraphrase Marie Antoinette, if the people are angry, let them have AC. That will encourage them to stay indoors and stop revolting.

Sources

1. Anderson, C. A. (2001). Heat and violence. Current Directions in Psychological Science, 10, 33-38.

2. Barber, N. (2000) The sex ratio as a predictor of cross-national variation in violent crime. Cross-Cultural Research, 34,264-282.

3. Baron, R. A. (1972). Aggression as a function of ambient temperature and prior anger arousal. Journal of Personality and Social Psychology, 21, 183-189.

4. Carlsmith, J. M. and Anderson, C. A. (1979). Ambient temperature and the occurrence of collective violence. Journal of Personality and Social Psychology, 37, 337-344.

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