Experiments are the only research method that allows us to isolate cause and effect. This is because in an experiment, strict control is maintained over all variables so that one variable can be isolated and examined.
For example, let’s say you want to teach high school students about AIDS, but you don’t know which teaching methodology would be most beneficial. You could design an experiment to examine this more closely. First, you choose a high school and randomly assign all the students to one of three groups. You might start by giving them a questionnaire about AIDS to establish baseline data about what they know or believe. Group 1 then listens to a lecture about AIDS, group 2 is shown a video, and group 3 listens to a person with AIDS talk about his or her experience. Strict care is taken to make sure that all of the information that is presented in these classes is identical. The only thing that differs is the teaching method. In scientific terms, the type of teaching method is the independent variable, which is manipulated by the researcher. After each class, the students are given a test to determine what knowledge they have gained about AIDS. This measurement is to determine the effect of the independent variable on the dependent variable, which in this case is knowledge about AIDS. If one group shows more learning after one particular method was used, we might be able to attribute the learning to the type of methodology that was used.
Experiments can be more costly than any of the other methods discussed, both in terms of finances and time commitment. It is also possible that in an attempt to control the experiments, a researcher may cause the study to become too sterile or artificial (nothing like it would be outside of the laboratory), and the results may be faulty or inapplicable to the real world. Finally, experiments are not always possible in certain areas of research, especially in the field of sexuality. For instance, what if we wanted to examine whether or not early sexual abuse contributed to adult difficulties with intimate relationships? It would be entirely unethical to abuse children sexually in order to examine whether or not they develop these problems later in life.