What distinguishes cross-sectional designs from longitudinal designs in developmental research?

• A. Cross-sectional studies track same individuals over time
• B. Longitudinal studies compare different individuals at one time point
• C. Cross-sectional compares different individuals at one time; longitudinal tracks same individuals over time
• D. They differ only in data analysis technique

Answer: (C)

The key idea is how researchers study change over time. Cross-sectional designs compare different individuals who are at different ages at a single point in time, giving a snapshot of age-related differences but not showing how any one person develops. Longitudinal designs follow the same individuals across multiple time points, so you can observe how each person changes over time and map developmental trajectories. This is why the correct description says cross-sectional compares different individuals at one time point, while longitudinal tracks the same individuals over time. Cross-sectional studies are quick and cost-effective but can be affected by cohort differences; longitudinal studies provide richer information about development but require more time and can face attrition.