A unique recent case of conjoined twins having a neural bridge connecting their brains raises some philosophical questions concerning mind sharing and the mind-body problem. From the article by Dominus in NYT (she personally spent 5 days with the family):
"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... When they were 2 years old, he performed a study in which Krista’s eyes were covered and electrodes were glued to her scalp. While a strobe light flashed in Tatiana’s eyes, Krista was emitting a strong electric response from the occipital lobe, which is where images are assembled. The test also worked when the girls switched roles... The results of the test did not surprise the family, who had long suspected that even when one girl’s vision was angled away from the television, she was laughing at the images flashing in front of her sister’s eyes.".
So there is good evidence that the brain bridge at least allows them to share "qualia". If a natural brain bridge can form it is likely that artificial ones can eventually be constructed also. If a researcher can observe external images of brain activity simultaneously with "qualia" in the mind wouldn't it make interaction between physical and mental subject to empirical study? Is it challenging to explain from dualistic mind-body perspective, does it strongly suggest a physicalist view?
The reporter herself is aware of philosophical issues with "sharing consciousness", she quotes Damasio's 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”.
But there is some evidence, admittedly tenuous, that this mental isolation may also be bridgable:
"Could the girls’ connection go beyond sensory impressions to higher thoughts, thoughts as simple as “I want water” or as complex as “I’m tired of ‘Good Night Moon’”? The family says that the girls often get up silently and suddenly and walk over to, say, a sippy cup, which Tatiana then immediately hands to Krista, who drinks from it... ‘I have two pieces of paper,” Krista announced. The girls sat at a small table in the living room, drawing, their faces, as always, angled away from each other. Each had one piece of paper. So I was surprised by Krista’s certainty: She had two pieces of paper?.. Was Krista using “I” to refer to both her and her sister?.. 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..."
Let's say for the sake of the argument that brain bridge does allow mutual access to "higher thoughts" and "I". My impression of some philosophies (e.g. phenomenology, existentialism, Bergsonism) is that they would treat "consciousness sharing", especially via a material link, as contradiction in definition. Is there one, and can such finding be explained away as an illusion, or would it challenge these views?