What type of research assesses the contributions of heredity and environment by comparing twins?

Twin studies are specifically designed to assess the contributions of heredity and environment to various traits and behaviors by comparing similarities and differences between twins. This type of research leverages the fact that identical twins share nearly 100% of their genetic makeup, while fraternal twins share about 50%. By analyzing how traits differ between identical and fraternal twins, researchers can isolate genetic influences from environmental factors.

This approach is particularly valuable because it allows for a clearer understanding of the degree to which genetics versus environment contributes to behavior, intelligence, psychological conditions, and other traits. For instance, if identical twins (who share the same genes) exhibit a higher correlation in a specific trait than fraternal twins, it indicates a stronger genetic influence. Conversely, significant differences can point to environmental impacts.

In contrast, longitudinal studies track the same individuals over time, case studies focus intensively on a single individual or small group, and cohort studies examine specific groups of people over time but do not necessarily involve comparisons between twins. Each of these methods serves different purposes in research, but they do not specifically compare the effects of heredity and environment in the way twin studies do.