We normally associate the arrival of warmer weather with positive experiences, such as vacations, walks on the beach and evenings eating on outdoor patios with friends. However, exposure to heat can also generate negative feelings that lead to socially inappropriate behaviour, such as excessive violence in sports.
When it is too hot, people become irritable and are more likely to believe that others are being hostile toward them. In response to these negative feelings, some people engage in violent and inappropriate behaviours.
This is especially true in the world of sports, where emotions already run high due to the competitive nature of the activity. An increase in temperature can become the straw that breaks the camel’s back and leads to violent behaviour in situations where it is neither desirable nor tolerated.
As researchers interested in how sports generate socially unacceptable behaviours, such as violence, we have been studying the influence of temperature on violent behaviour in Major League Baseball (MLB).
Violence in baseball
Violence is an appropriate behaviour in some sports. For example, in ice hockey and football, hitting an opponent to stop his or her progress may be the right thing to do to help your team win. However, the same act is wrong in other sports, such as baseball, where the rules prohibit violence.
In baseball, violence automatically results in the offending person being thrown out of the game. This is true for both physical violence, such as intentionally throwing the ball at an opponent, and verbal violence, such as insulting an umpire.
There are several factors that can lead baseball players and coaches to engage in violent behaviours. The desire to avenge a teammate who has been assaulted, the perception that the umpire has made an unfair decision and anger over an impending loss are just a few examples.
But in addition to these contextual factors, there is the question of how hot it is outside.
The influence of temperature on violent behaviour
The hypothesis that heat increases the level of violence in baseball has been explored by researchers in studies in 1991, 2011 and 2017. The results of all three of these research projects suggest that as temperatures increase, so does the likelihood of observing a specific violent behaviour — throwing the ball at an opponent.
However, it was not clear whether this is the case for other observable violent behaviours in baseball.
To determine if high temperatures have the same effect on all violent behaviours in Major League Baseball, we collected data from over 29,000 games where 2,322 people (players and coaches) were ejected as a result of various physical and verbal violent behaviours, between the 2008 and 2019 seasons.
From this data, we were able to observe that as the temperature increases, so does the likelihood of a player or coach being thrown out of a game. As an example, the probability of being ejected from the game in Major League Baseball is less than five per cent when it is 0 C, but six per cent for a temperature of 20 C and greater than seven per cent when the thermometer reads 40 C.
The results are similar for physical and verbal abuse, allowing us to conclude that heat has a similar effect on different types of abuse.
It is impossible to control the temperature outside in the hopes of reducing violent behaviour during baseball games, so the knowledge gained through our research project should be used to educate players and coaches on the potential effects of extreme heat.
Since excessive heat makes people more irritable and causes them to believe that others are more hostile, baseball players should learn that their aggressive impulses may be due to the temperature. By being better informed about the source of their discomfort, they may avoid reacting violently toward others.
Considering that global warming is expected to increase temperature extremes in the coming years, it is essential to consider the impacts of heat on socially unacceptable behaviours, such as excessive violence in sports. Although heat is not solely responsible for the adoption of aggressive behaviours, it is still an important factor to include in the equation. Our results add to those of many scientists who have already observed the role of heat in increasing violent behaviours, such as road rage, domestic violence and major crimes.
By improving the ability to control negative emotions when the mercury rises excessively, people will be able to enjoy the benefits that come with good weather, such as the incomparable atmosphere of a baseball stadium on a beautiful summer day.