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

The correct choice is twin study because this research methodology specifically focuses on understanding the relative contributions of genetic and environmental factors by comparing the similarities and differences between twins. In this approach, researchers analyze pairs of twins, often identical (monozygotic) twins who share nearly 100% of their genetic makeup, and fraternal (dizygotic) twins who share approximately 50% of their genes. By examining traits such as behavior, personality, intelligence, and various psychological characteristics, researchers can determine how much of those traits can be attributed to genetics versus environmental influences.

Twin studies are foundational in behavioral genetics as they allow for the dissection of hereditary influences from experiences and environmental conditions, providing a clearer understanding of how these elements interact to shape individual behaviors and traits. The evidence gathered through such studies can illuminate patterns that might not be evident through other research designs, making it a valuable method for exploring the biological basis of behavior.