A study once found that, for any given year, there was a rise in both ice cream consumption and the crime rate during the summer months. If ice cream consumption was high for a given year, the crime rate was also high; if consumption was low, the crime rate was also low. What can explain this chilling phenomenon?
Psychologists often use a Correlational Study to examine this type of situation. Correlational Studies are designed to study the relationship between two events. It is important not to confuse a correlational study with an experiment. A correlational study cannot prove cause and effect it simply shows a relationship. So then should I wear a bulletproof vest to Baskin Robbins in July? Let us explore the possible explanations.
One's first response to explain this relationship between crime and ice cream is that people are more aggressive during hot weather, they naturally eat more ice cream during hot weather and there is your explanation. Imagine my surprise when I started searching the web for data to support my hypothesis and found that crime rates actually decrease with increasing temperatures!
Another explanation for increased ice cream consumption and rising crime rates could be one of economic origin. Perhaps during times of economic hardship people are more likely to go out for an affordable treat such as ice cream, rather than an expensive dinner. I could not, however find any studies to support this idea. It has been reported that crime increases during economic hardship so this theory is not completely out of left field.
Ice creams vary in their ingredients from brand to flavor, but there are a few consistencies. All ice cream contains, milk, cream, eggs and sugar. Sugar is the only ingredient in this list that has been shown to have some effect on behavior. Perhaps someone should test the hypothesis that criminals eat more ice cream in the summer and therefore commit more crimes.
In evaluating this study I would have to say that it proves neither correlation nor causation. The study does not have internal validity and I highly question its external validity. Internal validity refers to the reliability of the study itself. To say that an experiment has internal validity means that the researcher can be reasonably certain that the independent variable caused the changes in behavior that was observed. External validity determines how well an experiment applies to real life. I would need a great deal more evidence to believe that ice cream causes crime.
Perhaps a better way to examine this phenomenon would be by method of the Ex Post Facto; this type of study falls somewhere between a correlational study and an experiment. In an Ex Post Facto study the researcher examines preexisting subject variables by forming groups based on the differences. For example, a researcher may put career criminals in one group and librarians in the other group and then determine how many in each group choose extra creamy rocky road. Unlike experimental research, the researcher in the Ex Post Facto study does not manipulate anything.
Greene, Dr. (2008). Drgreene.com http://www.drgreene.com/21_496.html
Myers, Anne, & Hansen, Christine. (2006). Experimental psychology. Thomson Wadsworth: Belmont,CA.
Vedantam, Shankar. (2006). The washington post. http://www.washingtonpost.com/wp-dyn/content/article/2006/08/06/AR200608060080_pf.html.