Final answer:
Ian likely found higher concordance rates for criminal tendencies among identical twins compared to fraternal twins, suggesting a genetic component to these behaviors. The Minnesota Study of Twins Reared Apart supports this idea, showing that identical twins have similar personalities regardless of their upbringing.
Step-by-step explanation:
If Ian is studying pairs of identical and fraternal twins and claims that his results suggest that criminal tendencies are due primarily to genetic factors, based on the principles of behavioral genetics, Ian most likely found A) Higher concordance rates among identical twins compared to fraternal twins. Concordance rates refer to the probability that a trait or behavior observed in one twin will be found in the other. Identical twins share 100% of their genetic material, whereas fraternal twins share only about 50%, like any other siblings. Therefore, higher concordance rates in identical twins imply a stronger genetic component to behavior.
Studies provide insights into the way our temperaments and abilities are shaped by genetic makeup versus social environment. The Minnesota Study of Twins Reared Apart demonstrated that identical twins, whether raised together or apart, tend to have very similar personalities. This suggests that some personality traits, including propensity for criminal behavior, may have a high heritability ratio, meaning they are likely influenced by genetics to a significant degree.