To meet them today you would imagine that they had known each other all their lives.
By Jane Beresford
Radio 4's Taking a Stand
They share an easy intimacy that belies the fact that identical twins Elyse Schein and Paula Bernstein spent their first 35 years in total ignorance of the other's existence.
Twins, Elyse and Paula met as strangers (Picture: Elena Seibert, 2007)
They were given up for adoption to separate families as part of an experiment in the US to discover how identical twins would react to being raised in different family backgrounds.
Neither set of adoptive parents knew the babies were part of a study or that they had been born twins.
The research project took place under the guidance of a leading US child psychologist with the co-operation of prestigious New York adoption agency Louise Wise Services.
It wasn't until Elyse Schein contacted the agency in 2003 to find out more details about her birth that the truth began to emerge.
"I received a letter that said: 'You were born on 9th October 1968 at 12.51 pm, the younger of twin girls.' It was unbelievable. Suddenly another element of my identity was revealed to me. Suddenly I was a twin."
When the agency contacted Elyse's newly discovered older sister Paula, the two women were quite quickly in touch and arranged to meet in a cafe in New York.
"Walking every step to that cafe felt momentous," says Paula. "I felt like this is it. From now on my life will forever be different."
When Paula saw Elyse for the first time, she was pleased to see that as similar as they looked, each was unique.
Elyse had just returned from working in Paris. "She looked very European," says Paula. "She had dark glasses on and was smoking a cigarette. She looked ultra cool. She was an alternative version of me.
"It was a relief I think for both of us that we were not carbon copies. As similar as we looked when we compared pictures of ourselves as kids, as adults we have our own distinct style."
"We both felt like asking: 'So what have you done with this body, with this DNA?'" says Elyse, "Or, 'So what have you been up to since we shared a womb?'"
Elyse and Paula have only photos to share of their separated childhoods
"We had the same favourite book and the same favourite film, Wings of Desire," says Elyse. "It was amazing," says Paula. "We felt we were conducting our own informal study on nature versus nurture in a way".
Having lost 35 years of shared experiences, the twins wanted to confront Dr Peter Neubauer about what had happened to them - although they discovered they had been dropped quite early on from the twins study.
At first he refused to speak to them but eventually agreed to a meeting. "It was quite surreal," says Paula, who recalls her twin sister's feelings that "we were his kind of 'lab rats' coming back to see the great doctor".
"We had all these questions for him. But he was very quick to turn the tables and it was clear that he was seeing this as an opportunity to continue his study," she says. "He wanted to see how we turned out and question us about our development."
Neither Paula nor Elyse feel they have received answers to all the questions they have. And the records of the study are sealed until 2066.
"It was obviously about nature versus nurture," says Paula. "But there were other issues that we thought they might have been interested in, one of them being about the hereditariness of mental illness."
From separate childhoods the twins have "adopted" each other (Picture: Elena Seibert, 2007)
And from their researches, the twins have learnt that their birth mother did spend part of her life in psychiatric care.
Nor do the women feel that they got what they wanted from Dr Neubauer. "I really was hoping that he would take responsibility for what he had done so many years ago," says Elyse.
"He refuses to be open to the possibility that they were wrong," says Paula. "No matter what, we can't make up for the 35 years that we lost. We are different people because of being separated.
"We don't regret the lives we've led, but meeting each other and the difficulties that we faced in our relationship, the absurdity of having to get to know a twin who was essentially a stranger is very painful".
Finding each other has been challenging as well as joyful. "For my husband and my brother too," says Paula, "you know in some ways I think it was a threat to them.
"My brother and I were always on an equal footing. We were both adopted and didn't know any biological siblings. And now suddenly I'm a twin. And who could be closer to someone than a twin?"
"What's funny is we've kind of come full circle," says Elyse. "We were initially twins, which was a biological bond, and then now I say that we've adopted each other. Now we're family by choice."
Elyse and Paula speak to Fergal Keane in Radio 4's Taking a Stand on 1 January 2008 at 0900GMT or afterwards at Radio 4's Listen again page.