46. Which of the following is typically regarded as the best evidence for a hereditary component in measured IQ?
Answer: E
Identical twins' IQs are more alike than are fraternal twins' IQs.
This finding suggests a strong hereditary influence on intelligence, as identical twins share 100% of their genetic material, while fraternal twins share only about 50%. The greater similarity in IQ scores among identical twins compared to fraternal twins provides compelling evidence for a genetic component in measured IQ.
A) Adopted children's IQs are higher than their natural parents' IQs.
While this observation may suggest some influence of the environment on IQ, it does not directly support the hereditary component, as it does not compare the genetic contributions of biological parents to the adoptive environment of the children. Therefore, it lacks the specificity needed to indicate a genetic influence on IQ.
B) Adopted children's IQs are more similar to those of their adoptive parents than of their biological parents.
This statement highlights the impact of the environment on IQ but does not provide evidence for a hereditary component. The similarity to adoptive parents could reflect environmental factors rather than genetic ones, making this choice less relevant in establishing the genetic basis for IQ.
C) Same-sex fraternal twins' IQs are more alike than are opposite-sex fraternal twins' IQs.
This finding may suggest some degree of environmental or social similarities among same-sex twins, but it does not provide evidence for a hereditary component in IQ. The comparison is not as strong as that between identical and fraternal twins, and it does not directly indicate genetic influence.
D) Children in enriched preschool programs show an increase in IQ.
While this demonstrates the importance of environmental enrichment on cognitive development, it does not address the hereditary aspect of IQ. This option focuses on environmental influences rather than genetic ones, making it less relevant to the question of heredity in IQ measurement.
Conclusion
Identical twins' IQs being more alike than those of fraternal twins provides the most compelling evidence for a hereditary component in measured IQ because it highlights the significant genetic overlap between identical twins. All other options either focus on environmental factors or do not provide a direct comparison of genetic influences, thereby failing to support the hereditary basis for intelligence as effectively as option E does.