What defines a "longitudinal study" in research?

A longitudinal study is defined by its ability to observe changes over time by following the same individuals or group across various points in time. This method allows researchers to detect patterns, trends, and long-term effects, providing crucial insights into how specific factors may influence outcomes over an extended period.

By observing the same subjects repeatedly, researchers can gather data that captures variability in behaviors, experiences, or conditions, which might not be visible in cross-sectional studies that only capture a snapshot at a single moment. Thus, the strength of longitudinal studies lies in their potential to illuminate developmental sequences or the effects of interventions, making them invaluable in psychology and other fields that explore changes over time.