The wide variety of strategies employed by psychologists to answer research questions.
Psychologists use a wide variety of techniques to answer research questions. The most commonly used techniques include experiments, correlational studies, observational studies, case studies, and archival research. Each approach has its own strengths and weaknesses. Psychologists have developed a diversity of research strategies because a single approach cannot answer all types of questions that psychologists ask.
Psychologists prefer to use experiments whenever possible because this approach allows them to determine whether a stimulus or an event actually causes something to happen. In an experimental approach, researchers randomly assign participants to different conditions. These conditions should be identical except for one variable that the researcher is interested in. For example, psychologists have asked whether people learn more if they study for one long period or several short periods. To study this experimentally, the psychologist would assign people into one of two groups—one group that studies for an extended period of time or to another group that studies for the same total amount of time, but in short segments.
The researcher would make sure that all the participants studied the same material, for the same total time, and were in the same study environment; the only thing that would differentiate the two groups is whether the learners studied for short or long segments. Thus, any difference in the amount of learning should be due only to the length of the study periods. (This kind of research has revealed that people learn better with several shorter study periods.) The experimental approach is useful when the research can establish control over the environment; this work is often done in a simple laboratory setting.
A second approach involves the correlational technique. This approach does not include control of the environment by the researcher. Instead, measurements are made as they naturally occur. For example, a group of high school students took two tests that required them to solve analogies and to recognize antonyms. The researchers discovered a correlation between students' abilities to complete analogies correctly and to identify antonyms. In general, students who were good at one task were also good at the other; students weak in one task were weak in the other. In correlational research, no attempt is made to state that one thing causes another, only that one thing is predictable from the other.
Correlational approaches are most useful when the researchers cannot control the environment or when the phenomena they want to study are complex. Instead of trying to simplify the situation, the researchers observe the complex behaviors as they naturally occur. A third approach is called naturalistic observation. This kind of research often is not highly quantitative; that is, observations are likely to be descriptive. The researcher decides on some class of behavior to observe and records the situations in which that behavior occurs and how it develops. A classic example of observational research was done by Jane Goodall in her work with chimpanzees in the wild. She spent years observing their social interactions and how the chimp "society" changed over time.
The previous techniques all involve observing a group of individuals. Sometimes, psychologists are interested in studying a single person in depth. This is called a case study. This approach is common when clinical psychologists work with a person over a long period of time. The final product in a case study is an in-depth description of a great number of different aspects of the individual's life and development. The strength of this approach is that detail is abundant; the weakness is that the psychologist cannot generalize to other people from the single individual being analyzed because that person may differ in important ways from the average person.
Finally, psychologists can use archival information to answer questions. Archival research differs considerably from the other approaches because it does not rely on direct observation or interaction with the people being studied. Rather, psychologists use records or other already existing information. For example, some psychologists were interested in whether the percentage of left-handed people in the population has remained constant throughout history. They obviously could not observe people who have died, so they decided to use existing information about the past. They recorded the percentage of left-handed people in paintings and other such renderings. After poring over paintings, they concluded that the percentage of left-handed people has not changed over the last few centuries. More commonly, archival information comes from birth and death records and other official statistics.
Cozby, Paul C. Methods in Behavioral Science. Mountain View, CA: Mayfield Publishing Company, 1993.