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Longitudinal and Cross-Sectional Research

🧠 Psychology By CampusDown Wiki Editorial Team Last updated
Quick answer: longitudinal research follows the same people over time to track change, while cross-sectional research compares different age groups at a single point to identify age differences.
Contents
  1. 1. Cross-sectional research
  2. 2. Longitudinal research
  3. 3. Sequential designs
  4. 4. In social surveys
  5. 5. References

Cross-sectional research

For example, children aged 5, 10 and 15 are measured at the same time in 2026 and their scores compared.

  • Strengths: quick, cheap, large samples and no attrition.
  • Weaknesses: shows group differences, not individual change, and confounds age with cohort effects arising from different birth years and experiences.

Longitudinal research

The same children are measured at 5, 10 and 15. Terman's study of gifted children, the Dunedin study in New Zealand and the Panel Study on Korean Children are examples.

  • Strengths: reveals within-person change, stability and the later effects of early experience.
  • Weaknesses: costly and slow, biased by attrition, affected by practice effects and outdated measures, and limited to one cohort.

Sequential designs

K. Warner Schaie proposed following several birth cohorts longitudinally. His Seattle Longitudinal Study found that intelligence declines little before late middle age, and that much of the decline seen in cross-sectional studies reflected cohort differences.

In social surveys

Social research often divides longitudinal surveys into panel studies (same respondents), trend studies (new samples from the same population) and cohort studies (the same cohort over time).

References

  1. Schaie, K. W. (1965). A general model for the study of developmental problems. Psychological Bulletin, 64(2), 92-107.
  2. Schaie, K. W. (2013). Developmental Influences on Adult Intelligence: The Seattle Longitudinal Study (2nd ed.). Oxford University Press.
  3. Santrock, J. W. (2021). Life-Span Development (18th ed.). McGraw-Hill.
  4. Babbie, E. (2021). The Practice of Social Research (15th ed.). Cengage.

Reports and materials that use this theory (Korean)

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This article was last updated on October 15, 2026. It is based on widely recognized original works and textbooks; when citing it in a paper, please check the original sources listed in the references.