November 7th, 2010 | Published in Science
These conjoined twins are joined on the head — and share brains:
They are the rarest of the rarest of the rare. Tatiana and Krista are not just conjoined, but they are craniopagus, sharing a skull and also a bridge between each girl’s thalamus, a part of the brain that processes and relays sensory information to other parts of the brain. Or perhaps in this case, to both brains. There is evidence that they can see through each other’s eyes and perhaps share each other’s unspoken thoughts. And if that proves true, it will be the rarest thing of all. They will be unique in the world. [...]
Among the more bizarre responses it engendered was a debate on the British student chat site The Student Room; the topic: “Conjoined twins sharing a brain—one person or two?”
The debate was of the angels-dancing-on-a-pin variety, as though science nerds had stumbled into a philosophy class. “I think it depends on whether they can develop their own personality,” opined one. “But then does that mean they are just one person with a very weird split personality disorder?” Added another: “If one is capable of thought that the other can’t interpret or won’t know about, then I’d say it’s two people. Otherwise I’d say it’s just one person with two functioning bodies.” [...]
Adding to the conundrum, of course, are their linked brains, and the mysterious hints of what passes between them. The family regularly sees evidence of it. The way their heads are joined, they have markedly different fields of view. One child will look at a toy or a cup. The other can reach across and grab it, even though her own eyes couldn’t possibly see its location. “They share thoughts, too,” says Louise. “Nobody will be saying anything,” adds Simms, “and Tati will just pipe up and say, ‘Stop that!’ And she’ll smack her sister.” While their verbal development is delayed, it continues to get better. Their sentences are two or three words at most so far, and their enunciation is at first difficult to understand. Both the family, and researchers, anxiously await the children’s explanation for what they are experiencing.
Really interesting. I’d also like to get a bucket of popcorn and watch theologians debate over this — it would be a circus.