science

the researchers note that the sister raised in the US had suffered three previous concussions

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the twin raised in Korea described growing up in a loving and harmonious family home, the adopted sister reported a harsher upbringing, colored by regular conflict and the divorce of her adoptive parents

It does seem as if there would be explanations for the unusual difference.

https://www.iflscience.com/identical-twins-raised-in-the-us-and-korea-display-surprising-iq-variations-71357