How we interact with the world is part of what makes us unique. But what if you saw and heard the exact same things as someone else?
Today on Think, writer Sam Kean talked about neuroscience and the story of conjoined twins who share their senses.
Krista and Tatiana Hogan were born in 2006 joined at the head. And that, Kean says, means they also share a part of their brain.
“And specifically, the part of their brain that is connected is a structure called the thalamus,” Kean says.
The thalamus acts as a relay center inside the brain. Most of the sensory input coming from our eyes and ears goes into the thalamus. That information is then fired out to muscles, nerves and other parts of the body.
Because the Hogan girls share a thalamus, they share that sensory information.
“So for instance, one girl could be taking a sip on her cup of juice, and the other girl can taste the juice in her mouth. If you tickle one of the girls, the other girl will laugh," Kean says.
Which actually sounds kinda cool. But then there are time like when the girls got into a shoving match.
“Finally, one of the sisters got sick of it, and she reached out and she slapped her sister in the face and then reached up and grabbed her own face in pain, because it hurt her to hit her sister like that.”
So when each experience binds you ever closer to someone else, are you really two people at all?
“It’s kind of an interesting question about whether they’re two individual people or whether they’re kind of one person in some sense," Kean says. "Because they are sharing sensory information, and in some sense, they’re even sharing their consciousness on some level. Because they are sharing thoughts about the world – they are aware of the same things going on around them.”
Despite all that the twins share, there are traits that distinguish the girls. One loves ketchup; the other hates it. And one really likes corn, which causes the other to break out in hives.
“Even though, on some physiological level, they’re experiencing the same thing, their response to it is quite different," Kean says. "It is, I think, evidence that they are individual people, despite sharing parts of their brain.”
Kean writes about the development of neuroscience in his book The Tale of the Dueling Neurosurgeons: The History of the Human Brain as Revealed by True Stories of Trauma, Madness, and Recovery.
Think re-airs tonight at 9, or find the podcast at kera.org/think.