Brian Boutwell in The Spectator:
First, what if later today the phone were to ring and the voice at the other end informed you that you have an identical twin. You would have lived your entire life up to that point not realising that you had a clone. The bearer of this news says arrangements have been made to reunite you with your long-lost sibling. In something of a daze, you assent, realising as you hang up that you’ve just agreed to meet a perfect stranger.
There was a time when separating identical twins at birth, while infrequent, did happen thanks to the harsh nature of adoption systems. One of the people who helped reunite many of them was the great psychologist Thomas Bouchard. I first read about Professor Bouchard’s work, wonderfully described by the psychologist Nancy Segal, when I was a graduate student. I still think about it often. What would it be like to live a large chunk of my life not knowing that I had a twin, and then meet him as an adult? Would our conversations ever go beyond polite small talk about the weather, sport or current events?
I’m sure similar thoughts went through the minds of the people in Bouchard’s study, and yet person after person realised — happily, I suspect — that they had a lot in common with the image of themselves sitting across the table.
More here.