Researchers have taken advantage of a rare opportunity to study identical (aka monozygotic) twins who were separated early in life, before being raised in different countries by different families – and there are some surprising results to report.
Whereas IQ has been shown to be up to 80 percent heritable – with twins usually scoring roughly the same on cognitive tests – in this case there was a substantial 16-point difference between the siblings.
There were, of course, lots of similarities between the pair, but the differences were also notable, suggesting that there needs to be a rethink of how much of our intelligence is down to our genes and how much of it is down to the environment that we’re brought up in.
The pair of twins were born in South Korea in 1974, and were separated at the age of two after one of them got lost in a market… The lost sibling was eventually adopted by a couple in the US.
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While the scores are clear, however, the reason for them isn’t. The US twin suffered three concussions as an adult, the researchers note, which made her feel like a “different person”. However, it’s impossible to say for sure whether this has affected the scores seen in the cognitive tests.
