Correlation vs. Causation

Recall from your textbook that a correlational study investigates the strength of the relationship between two variables. When thinking about correlational research, we must keep in mind that correlations are not the same as causation. That is, just because there is a relationship between two variables does not mean one variable caused the other.

Consider the following: A wealth of research shows that children who consume large quantities of media violence (e.g., watching television violence or playing violent computer or video games) are at greater risk for aggression and mental health problems than children who are not exposed to such content. For instance, a recent study involving 430 children in Grades 3–5 revealed that school-age children who were exposed to large amounts of media violence were more likely than their peers to engage in verbal, relational, and physical aggression, and they scored lower in measures of prosocial behavior (Gentile, Coyne, & Walsh, 2011).

So, does this mean media violence causes aggression in children? The answer is no. To determine causation, we must use an experimental research design. Experimental research requires the investigator to deliberately manipulate one of the factors, or variables (the independent variable) in order to determine its effect on the outcome, or behavior (the dependent variable). It also requires random assignment, an experimental group, and a control group. The control group includes participants who serve as a baseline, or starting point, for comparison with the experimental group. Ethically, we cannot recruit a group of children, randomly assign half to a group exposed to media violence and half to a group exposed to no media violence, and then measure aggressive behavior. Instead, we must rely on groups that already exist—i.e., children who consume large amounts of media violence and children who do not. With correlational research, we must also consider other factors that might contribute to the relationship between variables. When looking at the link between media violence and aggressive behavior in children, perhaps there are other factors at play. For example, aggressive children may seek out violent media, which contributes to and strengthens their aggressive tendencies. It is also possible that some parents are more lenient with their children’s media consumption, allowing their children to engage with age-inappropriate content.

Misinterpretations of correlational relationships occur frequently in the real world. Below are some examples of news headlines that may lead readers to misinterpret correlational findings with cause-and-effect relationships. (Recall that cause-and-effect relationships can only be determined in experimental research designs.)

“Hot and Bothered: Experts Say Violent Crime Rises with the Heat”

“Does Sugar Really Cause Hyperactivity?”

“Does MTV’s Teen Mom Prevent or Promote Teen Pregnancy?”

“Breast Implants Lower Cancer Risks but Boost Suicides”

“Facebook Users Get Worse Grades in College”

Google one of the preceding headlines and briefly summarize the research study. Next, answer the following questions:

Question 1

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Question 2

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Question 3

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Question 4

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____ research studies reveal cause-and-effect relationships.

Question 5

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Question 6

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Question 7

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The article presents an example of a correlational study. Even when two factors are strongly related, as is the case in this study, we cannot conclude that a causal relationship exists. In fact, there may be other factors that explain the correlation. In order to determine a causal relationship, the research must employ an experimental design. A true experimental design requires manipulation of one factor (the independent variable) thought to produce change in another factor (the dependent variable). Unlike correlational research, experimental designs also rely on random assignment, a control group, and an experimental group. None of these key elements of an experimental design were described in the study.