Final answer:
The study of twins, particularly identical twins separated at birth, shows that genetics has a significant impact on personality traits, evidenced by similar personalities despite different upbringings.
Step-by-step explanation:
The detail about the study of twins, specifically the Minnesota Study of Twins Reared Apart, contributes to the text by showing that genetics play a significant role in determining a person's personality traits. Despite being raised in different environments, identical twins tend to have very similar personalities, suggesting a strong genetic influence. The study found various personality traits, such as leadership, obedience to authority, a sense of well-being, alienation, resistance to stress, and fearfulness, to have a heritability ratio of more than 0.50. This doesn't mean that the environment has no effect on personality, but it does highlight the importance of genetics. Twin studies like this are important in understanding the balance between nature and nurture in human development.