Two identical twins raised in different countries show drastic disparities in cognitive abilities. However, their personality traits are very similar. Moreover, comparing the monozygotic twins’ characteristics sheds light on the nature and nurture debate.
The sisters were born in 1974 in Seoul, South Korea, and separated at the age of 2. One of the twins got lost in a market and ended up being adopted by a couple in the US.
The lost twin grew up stateside and was unaware she had any siblings until she submitted her DNA to a program in South Korea for reuniting family members in 2018. Two years later, she found out that she had an identical twin and an older brother and sister as well.
After reuniting, the twins did a series of tests to assess their intelligence, personality profiles, medical history, and mental health. The IQ of the twin raised in the US was 16 points lower than the Korean-raised sibling, which contradicts previous studies.
The study author says,
Moreover, researchers could not give a definitive reason behind the discrepancy, whether it was their upbringing or something else. However, the sibling in the US had suffered three concussions previously, which could have an influence.
Despite different life experiences, the similarities between the twins persisted, which highlights that genetics plays an important role in temperament.
They had similar health profiles and self-esteem. Moreover, both also underwent ovarian cyst removal through surgery.