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Two Little Girls–One Mind? June 2, 2011

Posted by Nina Rosenstand in Current Events, Nina Rosenstand's Posts, Philosophy of Human Nature, Science.
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Two little girls in British Columbia will grow up as conjoined twins;  they are craniopagus, connected at the head, sharing a part of their brain structure. Separating them is apparently not an option. That phenomenon, disturbing as it may be, is not in itself the reason why these little 4-year old girls are getting attention from cognitive neuroscientists. It is because they apparently share not only brain matter, but also sensory experiences:

Twins joined at the head — the medical term is craniopagus — are one in 2.5 million, of which only a fraction survive. The way the girls’ brains formed beneath the surface of their fused skulls, however, makes them beyond rare: their neural anatomy is unique, at least in the annals of recorded scientific literature. Their brain images reveal what looks like an attenuated line stretching between the two organs, a piece of anatomy their neurosurgeon, Douglas Cochrane of British Columbia Children’s Hospital, has called a thalamic bridge, because he believes it links the thalamus of one girl to the thalamus of her sister. The thalamus is a kind of switchboard, a two-lobed organ that filters most sensory input and has long been thought to be essential in the neural loops that create consciousness. Because the thalamus functions as a relay station, the girls’ doctors believe it is entirely possible that the sensory input that one girl receives could somehow cross that bridge into the brain of the other. One girl drinks, another girl feels it.

The girls surely have a complicated conception of what they mean by “me.” If one girl sees an object with her eyes and the other sees it via that thalamic link, are they having a shared experience? If the two girls are unique individuals, then each girl’s experience of that stimulus would inevitably be different; they would be having a parallel experience, but not one they experienced in some kind of commingling of consciousness. But do they think of themselves as one when they speak in unison, as they often do, if only in short phrases? When their voices joined together, I sometimes felt a shift — to me, they became one complicated being who happened to have two sets of vocal cords, no less plausible a concept than each of us having two eyes. Then, just as quickly, the girls’ distinct minds would make their respective presences felt: Tatiana smiled at me while her sister fixated on the television, or Krista alone responded with a “Yeah?” to the call of her name.

Although each girl often used “I” when she spoke, I never heard either say “we,” for all their collaboration. It was as if even they seemed confused by how to think of themselves, with the right language perhaps eluding them at this stage of development, under these unusual circumstances — or maybe not existing at all. “It’s like they are one and two people at the same time,” said Feinberg, the professor of psychiatry and neurology at Albert Einstein College of Medicine. What pronoun captures that?

The average person tends to fall back on the Enlightenment notion of the self — one mind, with privacy of thought and sensory experience — as a key characteristic of identity. That very impermeability is part of what makes the concept of the mind so challenging to researchers studying how it works, the neuroscientist and philosopher Antonio Damasio says in his book, “Self Comes to Mind.” “The fact that no one sees the minds of others, conscious or not, is especially mysterious,” he writes. We may be capable of guessing what others think, “but we cannot observe their minds, and only we ourselves can observe ours, from the inside, and through a rather narrow window.”

And yet here are two girls who can possibly — humbly, daily — feel what the other feels. Even that extraordinary dynamic would still put the girls on the continuum of connectivity that exists between ordinary humans. Some researchers believe that when we observe another person feeling, say, the prick of a pin, our neurons fire in a way that directly mimics the neurons firing in the person whom the pin actually pricks. So-called mirror neurons are thought to foster empathy, creating connections of which we are hardly aware but that bind us in some kind of mutual understanding at a neurological level.

The article, written by Susan Dominus (New York Times Magazine) who visited with the girls, includes several incidents that would indicate some form of shared sensory experience. I recommend that you read the rest of the article. The girls have not been studied extensively because of their young age, but if they remain healthy we may be treated to insight about one of the many ways of being human that just hasn’t been scientifically explored yet—the sharing of a mind…The philosophical implications of this phenomenon are overwhelming, to say the least.

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