Nature Vs. Nurture
Nature and nurture have been studied for a long time as scientists and psychologists are always curious as to what has more of an impact on an individual. To better understand child development, children with identical genetic makeups (twins) were separated at birth.
Source: Los Angeles Times
Dr. Viola Bernard (from the study) believed that separating twins was the only way to really understand them. Why? Because they grow up in the same environment and are typically treated similarly by their parents, so it can be difficult to determine which of their personality traits stem from nature or from nurture.