Final answer:
Owen and Ian are likely to have IQ test scores that are more similar than a random pair due to their shared environment and upbringing, even though Ian is adopted and not biologically related to Owen. Therefore, the correct option is C.
Step-by-step explanation:
Owen's biological parents adopted Ian, and Owen and Ian have lived together for their first 18 years. Based on research, it is likely that their IQ test scores will be more similar than a random pair. This is because, while intelligence has a significant genetic component, the environment in which children are raised can also influence their intellectual development. Living together in the same environment and experiencing similar educational opportunities and parental styles, Owen and Ian would likely show more similarity in their IQ scores compared to unrelated individuals in different environments.
However, since Ian is adopted and therefore not biologically related to Owen, their scores may not be as similar as those of biological siblings raised together. The Minnesota Study of Twins Reared Apart showed that even identical twins raised in different environments had higher correlations in their IQ scores than siblings or fraternal twins raised together, underlining the genetic component. Nonetheless, environmental factors still play a substantial role in shaping intelligence.
According to the research, shared environments like the one Owen and Ian have experienced can lead to some degree of similarity in IQ, supporting the idea that their scores would be more similar than those of a random pair (option c). This aligns with findings suggesting both genetic and environmental influences on IQ.