Final answer:
Longitudinal studies are research efforts where the same group of individuals is followed and observed over an extended period to understand how they change over time.
Step-by-step explanation:
Longitudinal studies enable the study of phenomena over time and may include an examination of historical records. These studies involve tracking a group of participants over an extended timeline to observe how their behaviors or characteristics change. This type of research is quite beneficial for exploring developments in human behavior and various aspects of life such as dietary habits, health changes, or educational progress.
Unlike cross-sectional studies that compare different segments of the population at a single point in time, longitudinal research provides insights into how the same individuals or groups evolve. An example of this would be observing a group's dietary habits at different stages of their lives. Such studies are incredibly important for contributing to our understanding of developmental stages and life-span changes.