Methods Used for Modern Research Developmental scientists must determine how to incorporate age into their research design. There are three general strategies for doing so; the study of different groups of people of different ages, called a cross-sectional design, the study of the same people over a period of time, called a longitudinal design, and the combining of cross-sectional and longitudinal designs in some fashion in a sequential design. What are the strengths and limitations of each of these designs? Other research methods are; systematic observation, self-reports, the clinical method, and ethnography. What are the similarities and differences of these methods? Let us now examine these fascinating topics.

Cross-Sectional, Longitudinal, & Sequential Designs Cross-sectional design studies groups of subjects that are selected at each of a series of ages. The results may seem to indicate that there are major changes based on age. However, cross-sectional data about adults can differ not only in age, but in cohort. Influences of this kind lead to cohort effects, findings that are the result of historical factors to which one age group in a cross-sectional study has been exposed. Cross-sectional studies cannot tell us anything about sequences of change over age, or about the consistency of individual behavior over time, because each subject is tested only once. Cross-sectional research is useful because it is relatively quick to do and can give us a glimpse of possible age differences or age changes. (Berk, 2010)

Longitudinal designs seem to solve the problems of cross-sectional research because they follow the same individual over a period of time. Each study of the same individuals allows us to look at sequences of change and at individual consistency or inconsistency over time. Because they compare performances by the same people at different ages, they get around the obvious cohort problem. Longitudinal designs, however, have several major difficulties. One problem is that longitudinal designs typically involve giving each subject the same test over and over again. Over time, people learn how to take the tests and the practice effects may distort the measurement of any underlying developmental changes. Another significant problem is that not everyone sticks with the program; some subjects drop out, others die or move away. Each successive testing includes proportionately more and more healthy adults, which make it look as if there is less change, or less decline, than actually exists. One way to avoid the shortcomings of both cross-sectional and longitudinal designs is to use a sequential design. A researcher using a sequential design would begin with at least two age groups. Investigators then test each group over a number of years. Each testing point beyond the initial one provides researchers with two types of comparisons—age-group comparisons like in a cross-sectional study, and comparisons of each group to itself at an earlier testing point like in a longitudinal design. Sequential designs also allow for comparisons of cohorts. Finding the same developmental pattern in two cohorts provides psychologists with stronger evidence than either cross-sectional or longitudinal data alone. (Berk, 2010)

Systematic Observation, Self-Reports, the Clinical Method, and Ethnography There exist many similarities among these different research methods, some of which are limitations. For example, reliability and external validity may be limited as the findings may be biased by the researcher’s values and theoretical preferences. Observer bias is also a danger. When observers are aware of the purpose of a study, they may see and record what is expected rather than what participants actually do. Even bias on part of the participants could exist resulting in them behaving in a way they would not normally, or giving answers to interview questions that are not factual.

It is the differences in the research methods that give them their strength. Systematic observation utilizes naturalistic observation to observe the behavior of children in their natural environment. Self-reports allow for the subject to give a complete account of details from their own point of view. While the clinical method brings together a wide range of information on one child, ethnography involves participant observation of a culture or distinct social group. (Hoey, 2012) Clearly, each method has its pros and cons and all can be beneficial.

Conclusion Thankfully, modern researchers have many methods and options available for them to make good use of. By carefully choosing which method to use in different scenarios, they are best able to present studies showing results that can be used as a basis for making improvements. Knowing the strengths and weaknesses, as well as the similarities and differences, researchers can choose wisely which method will provide the most benefit to the children of our society.

References
Berk, L. E. (2010). Development through the lifespan. Boston: Allyn & Bacon.
Dr. Hoey, B. A. (2012). What is Ethnography? Retrieved from http://www.brianhoey.com/General%20Site/general_defn-ethnography.htm