Descriptive vs. Causal research

Before talking about simple experiments, you may want to carefully explain the purpose of simple experiments (establishing cause-effect statements), explain the distinction between causal and descriptive questions (many students will not be able to tell you whether a question is a causal question or a descriptive question) and then defend the value of trying to answer causal questions. Begin by explaining that there are two approaches to scientific psychology:
(1) experimental psychology, which emphasizes controlling behavior and which is modeled after physics and
(2) correlational research, which emphasizes describing behavior and is modeled on astronomy (McGovern, Furumoto, Halpern, Kimble, & McKeachie, 1991).

Contrast the different conclusions to be drawn from a correlational study using random selection of participants versus the conclusions to be drawn from an experiment using random assignment of participants. (Handout 10.1 is also useful for illustrating that random assignment allows cause-effect statements).

Once students believe that experiments can lead to cause-effect statements, proceed to explain the value of causal research. Points to emphasize include:

a. If we isolate the cause of a problem, we may be on our way to devising a cure for the problem (as is often the case in medical science).

b. Causal research allows us to find out if a particular treatment is helpful in solving a particular problem. If so, it can be applied to a larger group. If not, the larger group is spared from the treatment.

c. Causal research not only allows us to predict and control behavior, but also to understand behavior. Understanding why people behave as they do may lead to better relations between people.

d. Causal rules often have a high degree of generalizability (e.g., gravity, reinforcement, conformity hold under a wide range of circumstances). Of course, we would test the generalizability of a causal rule in follow-up experiments.

e. Descriptive studies suggest causal relationships that can be tested in experiments. Thus, descriptive research can be a fertile source of ideas for experiments.

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