A longitudinal design or study is a kind of research design in which the same variables (people) are observed in repetition over the short and long-time period. Such a method of research is generally applied in clinical psychology and social-personality. The main reason for employing longitudinal research in both these field is to observe rapid fluctuations in behaviors, emotions and thoughts from time to time. This method of research is also employed in developmental psychology as well as sociology. Longitudinal research observes the same people, and so the diversity perceived in those variables are less inclined to be the result of cultural variations across ages.
