Study by Craig Anderson indicates that as the temperature outside
rises, so does violent crime.
When the phone calls started to come, Craig Anderson, professor and chair
of the psychology department, thought they were about his video game research.
Last spring, Anderson was in the media spotlight when his research on violent
video games landed him in front of a U.S. Senate committee. The subsequent
publicity resulted in media outlets from around the world contacting him.
This time the calls weren't on the study that said individuals who play
violent video games were more aggressive than those that didn't. Aggression
however does play a role in the psychology professor's latest research.
Anderson has published an article in the American Psychological Society's
Current Directions journal entitled "Heat and Violence." That
article caught the attention of Reuters news service and soon Anderson's
phone was ringing off the hook.
The article says that hot temperatures can increase aggressive motives and
behaviors in individuals. This conclusion is based on numerous studies conducted
in both field and laboratory settings.
"Laboratory studies show that hot temperatures increase aggression
directly by increasing feelings of hostility and indirectly by increasing
aggressive thoughts" Anderson writes. "Results (from several field
studies) show that global warming trends may well increase violent-crime
rates. Better climate controls in many institutional settings (e.g., prisons,
schools, the workplace) may reduce aggression-related problems in those
settings.
"Other studies show that hotter cities have higher violent crime rates
than cool cities," Anderson says. "Even when we statistically
control for population and social and economic factors like poverty and
unemployment rates, hotter cities will still have higher violent crime rates
than cool cities."
The article considered three different types of studies of heat and aggressive
behavior:
* Studies comparing geographic regions. Data in these field studies consistently
show that violent crime rates are higher in hotter regions than in other
regions of the United States.
* Studies comparing time periods. Field studies comparing aggression rates
in hotter versus colder time periods also support Anderson's hypothesis.
There are more than 2.6% more murders and assaults in the United States
during the summer than other seasons of the year. He also noted that hot
summers produce a bigger increase in violence than cooler summers; and violence
rates are higher in hotter years than in cooler years.
* Laboratory studies of aggression behavior. "In affectively neutral
and positive circumstances, hot temperatures cause increases in aggression,"
Anderson writes. "Recent lab studies show that even in affectively
negative circumstances, heat causes increases in initial retaliatory aggression."
For his field studies, Anderson studied violent crime rates in the US over
a 50-year period. He also sampled the 50 largest metropolitan areas in the
nation according to the 1980 census.
He found that increases in average annual temperature or global warming,
has an increasing effect on murders and assaults in this country, even after
controlling for a variety of other factors.
"For every one degree increase in average temperature, we can expect
an increase of 4.58 additional murders and assault cases per every 100,000
people," Anderson said.
"There are obviously other factors involved," he continued. "I
would never claim that temperature alone would be the main factor that causes
violent crime to be higher. However, there is now considerable evidence
from a variety of sources that suggesting that high temperature is one cause
that contributes to violent behavior, including violent criminal activity."
