Describe longitudinal design, and explain its strengths and weaknesses

Question

What will be an ideal response?

Answer 1

In a longitudinal design, participants are studied repeatedly, and changes are noted as they get older. The time spanned may be relatively short (a few months to several years) or very long (a decade or even a lifetime). The longitudinal approach has two major strengths. First, because it tracks the performance of each person over time, researchers can identify common patterns as well as individual differences in development. Second, longitudinal studies permit investigators to examine relationships between early and later events and behaviors. Despite their strengths, longitudinal investigations pose a number of problems. For example, participants may move away or drop out of the research for other reasons. This biases the sample so that it no longer represents the population to whom researchers would like to generalize their findings. Also, from repeated study, people may become more aware of their own thoughts, feelings, and actions and revise them in ways that have little to do with age-related change. In addition, they may become "test-wise." Their performance may improve as a result of practice effects—better test-taking skills and increased familiarity with the test—not because of factors commonly associated with development. The most widely discussed threat to longitudinal findings is cohort effects: Individuals born in the same time period are influenced by a particular set of historical and cultural conditions. Results based on one cohort may not apply to people developing at other times. But, cohort effects do not just operate broadly on an entire generation. They also occur when specific experiences influence some groups of individuals but not others in the same generation.