What type of study involves observing the same individuals at different points in their lives?

The correct answer is a longitudinal study. This type of research involves observing the same individuals over an extended period, which allows researchers to track changes and developments in behaviors, traits, or conditions as these individuals age. Such studies can provide valuable insights into developmental processes and how various factors influence individuals at different life stages.

In a longitudinal study, data is collected multiple times from the same subjects, which helps in understanding trends and changes over time that cannot be captured by single observations. This method is particularly useful in developmental psychology where researchers are interested in understanding how people grow, learn, and change throughout their lives.

The other study types mentioned are not focused on the same individuals over time. A cross-sectional study examines different individuals at a single point in time, which can highlight differences between age groups but cannot provide information about how individuals change over time. A meta-analysis combines results from multiple studies to identify overall trends but does not involve direct observation of individuals. A sequential design involves a combination of longitudinal and cross-sectional approaches, allowing researchers to observe different cohorts over time, but it still does not focus exclusively on the same individuals like a longitudinal study does.