Which of the following best describes the role of genetics and the environment using twin studies?

Question

BlackTom AI · Accepted Answer

Let’s restate the question to set the stage: Which option best explains how genetics and environment are interpreted through twin studies?
Option A says: 'IQ is highly correlated with identical twins (r=0.6) rather than fraternal twins (r=0.8).' This flips the typical interpretation, because a higher correlation for identical twins would suggest a stronger genetic influence, not a stronger environmental one, and the numbers given here would also imply the opposite relationship to what twin studies usually show. Therefore this option misattributes the signals from twin similarity.
Option B claims: 'IQ is highly correlated with fraternal twins (r=0.6) rather than identical twins (r=0.8).' Here the statement oddly assigns a higher correlation to fraternal twins and a lower one to identical twins, which contradicts the core finding of twin research where identical twins are more similar due to shared genes. This makes B conceptually incorrect.
Option C states: 'Looking at fraternal twins who were raised separately can better explain the impact of the environment, compared to assessing identical twins.' While studying twins raised apart can illuminate environmental effects, fraternal twins share, on average, less genetic similarity than identical twins, so their separation does not maximize the ability to isolate environmental impact relative to identical twins raised apart. In context, C undervalues the stronger relevance of identical twins raised apart for parsing genetics.
Option D asserts: 'Looking at identical twins who were raised separately can better explain the impact of the environment, compared to assessing fraternal twins.' This aligns with the classic twin-study logic: identical twins share nearly all their genes; if they are raised apart and still show high similarity, it points to genetic influence, whereas differences highlight environmental effects. When identical twins raised apart are compared to fraternal twins raised apart or together, the design more cleanly teases apart genetic and environmental contributions, making D the best description of the role of genetics versus environment in this context.
In summary, A and B misstate which twin type shows greater similarity and misinterpret the direction of genetic influence. C mischaracterizes the environmental exposure advantage, underestimating the value of identical twins raised apart for disentangling genes from the environment. D correctly captures the essence of twin-study methodology: identical twins raised apart provide a clearer window into environmental impact relative to fraternal twins, due to their near-identical genetic makeup.

Which of the following best describes the role of genetics and the environment using twin studies?

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