Research is a cornerstone of Psychology. All of its theories on human behavior can only be proven through exhaustive research and study. A researcher tries to prove a theory or answer a question by gathering data relevant to the issue and analyzing them. As such, being able to design a reliable and valid data-gathering system is of utmost importance. One of the most common areas of research in Psychology is developmental or changes over a period of time. There are two basic designs or methodologies for gathering data for this type of research – the longitudinal design and the cross-sectional design. This paper will take a more comprehensive look at the cross-sectional data design, when and why it should be used, what are its limitations, and how this method is applied in actual research.
Cross-sectional and longitudinal designs study the changes that occur in an individual over time. In longitudinal, a particular behavior is observed in one person or group, and the changes or developments of the specific behaviors are repeatedly observed and recorded over time. Cross-sectional design aims to do the same thing, but rather than take a single group of the same ages and repeatedly test them as they grow older, this design takes a group of individual of different ages of developmental stages, and compare how the specific behavior is different from one age group to another. For example, the premise is that a researcher wants to study how the reading skills progress in an individual. In a longitudinal design, the researcher will assemble a group of children of the same age, give a baseline assessment of their reading skills, and then observe how these reading skills develop as time passes. Obviously, employing the longitudinal design requires a huge investment in time because there is no way to make the children grow older faster. The researcher must patiently wait for this natural process take place.
Advantages of the Cross-sectional Method
Using the cross-sectional method for collecting data is very informative because it can document differences as a function of the developmental phase. (Morf et al 2004: 409) In cross-sectional design, there is no need to wait for the developments to take place because you take a group of people at various developmental stages and compare and contrast the specific behaviors that is being studied. All at once, you can analyze how the reading skills are different at different age levels. Gavin Bremner said that most developmental researches prefer the cross-sectional design to gather their data “because it is the least time-consuming and provides a quick estimate of changes with age.” (2003: 9) Cross-sectional design is the fastest way to get the data if the researcher does not have the luxury of time. Consequently, because the data can be gathered in les time, it also means that it is less costly to pursue. If you are studying reading skills, all you have to do is assemble a group of children at various developmental ages and then observe, record, and analyze their behavior. All the data that you need can be gathered in a few quick sessions and all the participants are available; assembled together in one place and time. Another very important advantage of using the cross-sectional design for data gathering is that there is less attrition in terms of your participants. Attrition in this case refers to a situation where the children no longer want to participate in the study. Because the individuals are observed all in one go, in one or two sessions, the risk of them losing interest in participating is very low. For a researcher, this is very important because changing the subjects of your study in the middle of the experiment puts the validity of the research at risk. A research presupposes homogeneity in the subjects being studied. With a longitudinal design, there is a greater possibility for the participants to drop out of the study because of the time element.
Disadvantages of the Cross-sectional Method
Of course it is worth noting that a cross-sectional design also has its limitations. One common criticism is that the cross-sectional design is prone to selection bias. This means that the researcher may have some hidden reasons for choosing the participants of the study. In other words, the selection may not be as random as the research requires. There are underlying reasons why a researcher chooses one child over another, and the researcher must be aware of these reasons, and give it proper consideration. The possibility of a selection bias cannot be discounted into the equation. This is very important to keep in mind because the selection might be made in order to get the desired results or prove the premise of the researcher. This threatens the internal validity of the experiment. Moreover, there are individual differences among the participants, such differences may be socio-economic, emotional, cognitive, among others, which can affect the behavior. The researcher must always take these differences into account when analyzing the data. Another common criticism of the cross-sectional design is that while it does give a good description of a particular behavior across different cohorts of age groups, using the cross-sectional design cannot capture the actual developmental processes or stages of the target behavior as it occurs in an individual. As Bornstein puts it, “the cross-sectional method only provides information about age differences, not age-related change.” (1999: 52) As such, “there is no way to derive an estimate of the continuity or discontinuity of various processes over age” (Bremner 2003: 9) To simplify, a cross-sectional method does not document the changes in the behavior as it takes place over time, it merely describes the differences between and among cohorts or age groups. The cross-sectional method cannot say whether the change or changes in the behavior took place in a fluid, continuous manner or in discrete, staggered steps.
Uses of the Cross-sectional Method
Both the cross-sectional and longitudinal designs are of particular importance in developmental psychology because age is considered as the major determinant of the changes that children undergo as they get older. The concept of developmental milestones is the result of exhaustive researches made using data gathered from cross-sectional and longitudinal designs. These developmental milestones are certain behavioral, cognitive, physical, and emotional characteristics that take place universally among all individuals, from birth until 7 years old. While the development may be slower in some individuals and faster in others, they occur more or less around the same time. A significant delay in the manifestation of these developmental milestones may point to an underlying cause which may or may not be medical in nature.
Cross-sectional is ideally used to describe observed behavior changes across cohorts. As Ilardi (2003:216) writes, “cross-sectional designs, which gather data at only one point in time, set the stage for longitudinal research.” This means that cross-sectional is best used as an introductory research, setting the premise or context for the generation of information from which deeper, more complex questions will arise. From these questions, a more comprehensive and complex study can then be undertaken. For example, a researcher has observed that individuals of various ages handle peer pressure differently. The researcher then proceeds to prove the hypothesis by conducting a study using the cross-sectional design. From the data, the researcher was able to conclude that younger people are more prone or vulnerable to peer pressure and thus, have a greater need to feel accepted within their own social group. From the findings of the cross-sectional designed study, the same researcher or other researches, getting their cue from the findings, can then proceed to study other related aspects of the initial experiment. From the cross-sectional findings, researches can then use the longitudinal method to determine how the ability to handle peer pressure develops as one matures in age.
Indeed, a strong cross-sectional study is the foundation of sound researches in developmental psychology. By confirming that differences indeed exist or developments indeed are taking place, then researches can then proceed to finding out why the differences in behavior exist at different age levels and how these differences develop or take place. In a sense, the cross-sectional method of data gathering is the reason why developmental psychology exists in the first place. Developmental psychology is anchored in the concept that development takes place universally among all individuals. These developments are manifested in behavioral, cognitive, emotional, and physical changes. And given one specific behavior or domain, the cross-sectional method allows researches to capture the differences that exist in individuals of different ages and confirm that such differences indeed are present. From here, researches can make a generalization, and proceed to finding out more about how the development occurs in each person and what are the factors that encourages or suppresses said development. Studies can also be made to analyze the occurrences of deviant behaviors and how they can be prevented or repaired.
References:
Bornstein, M. H & Lamb, M. E. (1999). Developmental Psychology: An Advanced
Textbook. Lawrence Erlbaum Associates
Bremner, G, et al. (2003). An Introduction to Developmental Psychology. Blackwell
Publishing.
Ilardi, S. S. & Roberts M. C. (2003). Handbook of Research Methods in Clinical
Psychology. Blackwell Publishing
Morf, C. C. & Sansone, C. (2004). The Sage Handbook of Methods in Social Psychology.
Sage Publications
