Because distortion can be a serious limitation of survey research, scientists may choose to observe subjects' behavior directly through observational research. Observational research takes place in either a laboratory (laboratory observation) or a natural setting (naturalistic observation). In either research method, observers record participants' behavior within an environment. Observational research reduces the possibility of subjects giving misleading accounts of their experiences, not taking the study seriously, being unable to remember details, or feeling too embarrassed to disclose everything that happened.
Observational research has limitations, however. Volunteer bias is common, because volunteers may not be representative of the general public. Individuals who agree to be observed and monitored may function differently than respondents who do not want to be observed and monitored. Individuals may also function differently in a laboratory setting than respondents who are observed in more‐natural settings.
A developmentalist may also conduct correlational research. A correlation is a relationship between two variables (factors that change). Variables may include characteristics, attitudes, behaviors, or events. The goal of correlational research is to determine whether or not a relationship exists between two variables, and if a relationship does exist, the number of commonalities in that relationship. A researcher may use case‐study methods, surveys, interviews, and observational research to discover correlations. Correlations are either positive (to +1.0), negative (to–1.0), or nonexistent (0.0). In a positive correlation, the values of the variables increase or decrease (co‐vary) together. In a negative correlation, one variable increases as the other variable decreases. In a nonexistent correlation, there is no relationship between variables.
Although correlation is commonly confused with causation, correlational data does not indicate a cause‐and‐effect relationship. When a correlation is present, changes in the value of one variable reflect changes in the value of the other. The correlation does not imply that one variable causes the other variable, only that both variables are somehow related. To study the effects that variables have on each other, an investigator must conduct an experiment.
Experimental research is concerned with how and why something happens. The goal of experimental research is to test the effect that an independent variable, which the scientist manipulates, has on a dependent variable, which the scientist observes. In other words, experimental research leads to conclusions regarding causation.
A number of factors can affect the outcome of any type of experimental research. For instance, investigators face the challenge of finding samples that are random and representative of the population being studied. Additionally, researchers must guard against experimenter bias, in which their expectations about what should or should not happen in the study sway the results. Researchers should also control extraneous variables, such as room temperature or noise level, that may interfere with the results of the experiment. Only when experimenters carefully control extraneous variables can they draw valid conclusions about the effects of specific variables on other variables.
Western cultural standards do not necessarily apply to other societies, and what may be normal or acceptable for one group may be abnormal or unacceptable for another group. Sensitivity to others' norms, folkways, values, mores, attitudes, customs, and practices necessitates knowledge of other societies and cultures. Developmentalists may conduct cross‐cultural research, research designed to reveal variations existing across different groups of people. Most cross‐cultural research involves survey, direct observation, and participant observation methods of research. The challenge of this type of research is to avoid experimenter bias and the tendency to compare dissimilar characteristics as if they were somehow related.
Participant observation requires an observer to become a member of his or her subjects' community. An advantage of this method of research is the opportunity to study what actually occurs within a community and then consider that information within the political, economic, social, and religious systems of that community. A disadvantage of participant observation is the problem of subjects altering their behavior because, as subjects of the observation, the participants know that they are being watched.