How do twin studies contribute to understanding genetic influences on behaviour?

How do twin studies contribute to understanding genetic influences on behaviour?

• A. Compare monozygotic and dizygotic twins to estimate heritability; higher concordance in MZ suggests genetic influence
• B. Compare siblings to evaluate environment only
• C. Use twins to measure IQ differences in only identical pairs
• D. Twin studies show no genetic influence on behavior

Answer: (A)

Twin studies target how much genes shape behavior by comparing how often both twins show a trait. Monozygotic twins share nearly all their genes, while dizygotic twins share about half. If a trait is strongly influenced by genetics, monozygotic twins will be more concordant (both showing the trait) than dizygotic twins. When the concordance is similar for both types of twins, it points to environmental factors playing a larger role. For example, a much higher rate of both twins exhibiting a trait in identical twins than in fraternal twins suggests a genetic contribution. The other ideas either ignore genetic differences, rely on a limited or inappropriate comparison, or claim no genetic influence at all, which contradicts what twin-concordance patterns reveal.

Twin studies target how much genes shape behavior by comparing how often both twins show a trait. Monozygotic twins share nearly all their genes, while dizygotic twins share about half. If a trait is strongly influenced by genetics, monozygotic twins will be more concordant (both showing the trait) than dizygotic twins. When the concordance is similar for both types of twins, it points to environmental factors playing a larger role. For example, a much higher rate of both twins exhibiting a trait in identical twins than in fraternal twins suggests a genetic contribution. The other ideas either ignore genetic differences, rely on a limited or inappropriate comparison, or claim no genetic influence at all, which contradicts what twin-concordance patterns reveal.