What is a limitation of using cross-sectional norms?

• A. They show how an individual changes over time.
• B. They provide a snapshot in time and do not show within-person changes.
• C. They require extensive longitudinal data collection.
• D. They are not based on any population data.

Answer: (B)

Cross-sectional norms provide a snapshot in time, comparing many individuals at one moment rather than tracking a single person over time. This means they can show how different age groups compare at that moment, but they can’t reveal how an individual changes across the lifespan. The observed differences across ages may also reflect cohort effects—differences arising from the unique experiences of each birth cohort rather than true developmental change. So, the limitation is that you can’t see within-person changes over time from cross-sectional data.