The Two Halves Of The Brain See The World In Very Different Ways : Shots - Health News Surgery that severs the link between brain hemispheres reveals that those halves have way different views of the world. We ask a pioneering scientist what that tells us about human consciousness.

The Roots Of Consciousness: We're Of 2 Minds

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NPR's Invisibilia, the show about human behavior, has returned with a new season of stories about the invisible forces that shape our lives. This week, they're looking at how ideas and concepts from our culture get into our heads and influence what we do.


Sometimes, that happens in ways that are unexpected and bizarre. Here's Hanna Rosin with a story of what one woman experienced after brain surgery.


UNIDENTIFIED MAN: I don't know if you talk with your hands or anything, but...




BYRNE: (Laughter).


ROSIN: Recently, my co-host Alix Spiegel and I called a woman named Karen Byrne. In her late 20s, Karen had gotten this very serious operation on her brain. The operation was to treat Karen's epilepsy, which was so bad that Karen was having near-constant seizures. So her doctors put her to sleep and cut into her brain. And Karen says when she woke up, her speech was a little funny. But, basically, she felt great.

BYRNE: I had woken up. And I was sitting on the hospital bed, talking to my surgeon. And...

ROSIN: And then, all of a sudden, her left hand picked itself up and started moving towards her shirt, started delicately undoing its pearly top button.

BYRNE: My hand was taking my clothes off.

ROSIN: Taking your clothes off?

BYRNE: Yeah. My hand was taking my shirt off (laughter).


ROSIN: And you didn't have any thought like, I'd like to take my blouse off now.

BYRNE: No, no, no, no. It just started to do it.

ROSIN: Karen, of course, was completely shocked. And so was her surgeon.

BYRNE: (Laughter) And the surgeon was like, Karen, do you realize what's happening? I said, yeah. Something's wrong.


ROSIN: And then, all of a sudden, the hand seemed to get angry.

BYRNE: It was tearing the buttons off the shirt.

ROSIN: Karen kept telling it to stop.

BYRNE: Knock it off. Knock it off. Knock it off.

ROSIN: Her surgeon was screaming at her to control it.

BYRNE: Try to make it stop. I said, I can't. It won't stop it. And then I started to just cry. I just didn't know what to do.

ROSIN: Eventually, they wrestled her hand down. But what was so troubling was that this didn't seem like some strange, physical spasm. The hand acted like it had intent.

Did the hand seem to have...

BYRNE: A different mind?

ROSIN: Yeah.

BYRNE: Yes. Yes. Yes. Yes. It did seem to have a different mind.

ROSIN: When Karen went home from the hospital, the hand - this new hand with a mind of its own - went with her. A lot of the time, the hand was OK. But it would also get really upset with her. Like, sometimes, when Karen did something it didn't like...

BYRNE: Smacked me right across my face.

ROSIN: Your own hand.

BYRNE: Yeah, right across my face, right across my face.

ROSIN: Sometimes, it would hit her so hard it left her black and blue.

BYRNE: Yeah.

ROSIN: Her problem, the doctors explained, was alien hand syndrome. See, to cure her epilepsy, they'd had to sever the two halves of her brain.

BYRNE: Brain was split in half.

ROSIN: They cut right down the center between the two lobes. This wide, flat bundle of neural fiber with one of those brainy-sounding names...

BYRNE: Corpus callosum. Yeah.

SPIEGEL: It's like the thing that gets the two halves to speak to each other?

BYRNE: Yeah. Yeah. Yeah.

ROSIN: So without her corpus callosum, her right hemisphere and her left weren't communicating perfectly well. Her right hand seemed to be getting directions primarily from her left hemisphere. And her left hand - this new alien hand - seemed to be getting directions primarily from her right hemisphere. And so what Karen got to see more clearly than most of us was that there really were very different parts of her.

BYRNE: For some reason, my own hand felt some animosity towards me.

ROSIN: Or not her hand, really. Some part of her mind.

BYRNE: Half my brain just didn't particularly care for me too much. I wasn't pleasing it.

ROSIN: And at first, Karen couldn't make sense of what this other part wanted, why it was getting so angry. But as time went on, she saw a distinct pattern and came up with a theory of what that part of herself wanted. Now, this is not science. It's just how Karen sees it. She says she thinks her hand wants her to be more moral.

BYRNE: It's trying to make me a better person.

ROSIN: Basically, her alien hand was trying to enforce all these messages that she'd picked up from her culture about what she should be.

BYRNE: Not to smoke and not to curse. And be nicer to others.

ROSIN: And when Karen deviated from those cultural norms, it would punish her. Take for example what her alien hand does when she tries to smoke.

BYRNE: When I go to light a cigarette, the hand will either put the cigarette out or flick the ashes around.

ROSIN: Karen hadn't quite realized just how deeply these cultural messages had penetrated. And though she's learned to live with it - she's in her 50s now - she's not always happy with it.

BYRNE: Oh, it's such a pain in the rear end. It really is. I understand that you want me to quit. But cut the crap.


BYRNE: (Laughter).

ROSIN: Hanna Rosin, NPR News.

CORNISH: Invisibilia has a new episode this week. It's out now, and it dives deeper into how cultural concepts affect our behavior and our biases.

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