SPEAKER: You're listening to Short Wave from NPR.
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EMILY KWONG: Hey, Short Wavers. It's Emily Kwong.
RACHEL CARLSON: And Rachel Carlson, Short Wave producer. And, Emily, I think it's pretty safe to say that both of us read the team inbox, shortwave@npr.org.
KWONG: Every morning, fervently.
CARLSON: Exactly. And two months ago, you said something to reporter Jon Hamilton that really piqued our audience's interest.
KWONG: I don't have an inner monologue.
JON HAMILTON: Not everybody has an inner monologue. This is something that doesn't work for everybody.
KWONG: Ha! I'm safe--
HAMILTON: Yeah, exactly.
KWONG: --from the BTIs.
HAMILTON: But if you--
[LAUGHTER]
KWONG: I'm so proud of myself.
CARLSON: And our inbox lit up about this. People wrote, is that even a thing? I don't understand. How is that possible? So we had to confirm science backs this up, right? Not everyone has an inner monologue.
KWONG: It is true. Scientists confirm, for some people, inner speech is far less wordy. So my inner experience isn't really word-based. It's more like a moving landscape of images. It's kind of like soaking in an emotional bath and, like, feelings.
CARLSON: I love it.
KWONG: Yeah. And feelings and images will rise, and they'll fall. But there's no words. It's-- it's real silent.
CARLSON: Mine is loud.
KWONG: Oh, no.
CARLSON: It does not feel like a bath.
[LAUGHTER]
CARLSON: It feels like it's dialogue heavy. So--
KWONG: Oh.
CARLSON: --whether it's a conversation that I'm having with myself or an imagined conversation with other people, yeah, it's a screenplay. [LAUGHS]
KWONG: Me, myself, and my voice.
CARLSON: Yeah, totally.
KWONG: La, la, la, la, la.
CARLSON: But, Emily, this got us thinking about how different the insides of people's heads are. And it turns out, there are scientists who study what's going on in people's minds.
RUSSELL HURLBURT: I think it's the most interesting question on the planet. The earliest known writings, like Gilgamesh or whatever you call the earliest writings are interested in inner experience.
KWONG: This is Russell Hurlburt, a psychologist at the University of Nevada. And Russ is a legend in the field for being one of the first to gather data on inner experiences through a beeper.
CARLSON: Participants carried this device around. And every time it beeped--
[BEEP]
CARLSON: --they filled out a questionnaire to quantify their inner experience. But there was a problem.
HURLBURT: People didn't know what they were talking about when they picked a number on a Likert scale, and I didn't know what they were talking about. The data was just rotten on the way in.
KWONG: So he ditched the questionnaires and instead told participants, every time the beeper goes off, write down what's going on internally in your own words.
HURLBURT: And then we get together and talk about it.
KWONG: Russ called this technique descriptive experience sampling. It was illuminating, sometimes even life-changing for the participants involved. But Russ is the first to say how highly imperfect his method is.
CARLSON: It's just people saying what's going on in their heads. But how do you confirm?
KWONG: Yeah. Like, how do you check for accuracy? Like, he believes that people do not fully know the characteristics of their inner experience, including me.
HURLBURT: You've got no good reason to be confident that you do or do not have an inner monologue, because there's just too many layers between what your inner experience actually is and what you might say about it.
KWONG: That was humbling to hear.
CARLSON: It's humbling, yes. But Emily, even if people can't fully know themselves, scientists are still trying to figure it out, including a collaborator of Russell's, Charles Fernyhough.
CHARLES FERNYHOUGH: We've shown that you can do it, not just us. Teams all around the world have shown that you can study this stuff. You can have a science of it.
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KWONG: So today on the show, how far can the science go in the quest to know thyself? I'm Emily Kwong.
CARLSON: And I'm Rachel Carlson. You're listening to Short Wave, the science podcast from NPR.
KWONG: OK, Short Wavers, Rachel and I are here with Charles Fernyhough. He's a professor of psychology at Durham University and studies inner speech, which is one of many kinds of internal experiences.
CARLSON: Charles, what do we know about where inner speech and what parts of the brain are involved?
FERNYHOUGH: Well, if you watch any small child, you're really likely to see them talking to themselves.
CARLSON: Yes.
FERNYHOUGH: So when kids are talking to themselves out loud, we call that private speech. And the idea is that it's the precursor. It's the thing that before inner speech. So the inner speech that you and I probably experience, or may not, [LAUGHS] where that from developmentally is from private speech. And in turn, that private speech came from the social dialogues that that that kid enjoyed when they were growing up-- so, you know, talking to caregivers, other adults, other children. And gradually, internalizing those conversations, they become conversations with the self.
CARLSON: Wow.
KWONG: You're saying basically, like, because we're born into this social world with all these people around, like, my niece's little monologue when she's, like, talking to herself will eventually become internalized, and that is her inner speech.
FERNYHOUGH: Yeah, exactly. That is the-- it's the theory of a great Russian psychologist called Lev Vygotsky, who was writing this stuff about 100 years ago. His work has become increasingly influential in recent years, and it's a really simple, neat little theory that nobody has got to the bottom of yet because it is so rich, and it has such implications for the way our minds work.
CARLSON: Where is that in the brain? Or where can we see it in the brain?
FERNYHOUGH: Well, as you'd expect, you see the language systems that we know about mostly lateralized onto the left hemisphere a bit towards the front called Broca's area, which is often involved in producing, you know, complex action patterns, a bit further back, called Wernicke's area, which is responsible for processing speech, including speech from other people. Those two areas create a kind of resonating loop, which always shows up when we ask people to speak to themselves or out loud in the scanner.
KWONG: What kind of scanner, like, a CT scanner, an MRI scanner?
FERNYHOUGH: These days, it's going to be an MRI scanner, yeah, when we're doing fMRI--
KWONG: OK.
FERNYHOUGH: --research on the topic. So we see these systems lighting up. But, I mean, that bit at the front, Broca's area, lights up when we do a whole load of different things, so we can't really pin too much onto that. So we know it's important, but it's not the whole story.
CARLSON: How so?
FERNYHOUGH: So one of the things that we've argued, if inner speech comes from a dialogue with other people, it should have the structure of a dialogue. In order to do that, your language system has got to be working, all that stuff on the left hemisphere that you'd expect to be working. But some other stuff must be going on as well.
CARLSON: Oh, interesting. OK. So you're saying that would involve more parts of the brain than just the language areas?
FERNYHOUGH: Yeah. And what we find when we look at people doing dialogic inner speech as opposed to something that's more like a single line of conversation, is that, yes, you get that language system in the left hemisphere firing, but you also get another region way on the other side of the brain, which we know from previous research is involved in representing other people's minds. So you're representing yourself as a partner in that conversation.
CARLSON: Wow.
KWONG: Wow. We heard from Russell Hurlburt how there's, like, limits to surveying. Like, you can't really know what's going on in someone's inner experience fully, nor can they. How has the addition of scanning deepened our understanding of inner speech or complicated it to the point where maybe we-- there's even more that we don't know?
FERNYHOUGH: The cool thing about working with Russ was that we had a study where we got people used to using descriptive experience sampling.
CARLSON: The beeper.
KWONG: Yeah.
FERNYHOUGH: Yeah, the beeper, yeah. They got used to using the beeper. Once they got pretty good at it, we then put them into the scanner. And we saw what they were doing.
KWONG: Wow.
FERNYHOUGH: So we had two kinds of inner speech. We'd sort of caught two kinds of fish.
KWONG: Oh, gosh.
FERNYHOUGH: One is the elicited inner speech where you're told to do it, and the other is the spontaneous inner speech where you're not told to do it. It just happens. And we could look to see whether these two kinds of things were the same. And we've got a whole lot further to do on this topic. But what we found is they didn't look the same in terms of that balance of activation between Broca's area and Wernicke's area. So when we had elicited inner speech, there was lots of that Broca's area, the bit at the front on the left that's producing, producing, you know, doing these high, complex movement patterns, including speech. But when people were doing inner speech spontaneously, there was much less of that.
KWONG: Right. Just like chilling in the machine, and they just had an errant thought. That was inner speech.
FERNYHOUGH: Exactly.
KWONG: Yeah.
FERNYHOUGH: And it was more of that-- that region bit further back.
KWONG: Wow.
FERNYHOUGH: --the Wernicke's area.
CARLSON: Wow.
FERNYHOUGH: That is more the kind of listening, hearing bit of the brain.
KWONG: OK, yeah.
FERNYHOUGH: You know, the exact areas of the brain doesn't matter too much. But for us, it was a really important sign that more needed to be done here and that we shouldn't assume that when you put somebody in the scanner and tell them to do something, the thing that results is anything like--
CARLSON: [LAUGHS]
FERNYHOUGH: --the thing you're actually interested in. So neuroscientists beware. You know, are people really doing the kind of thing in the scanner that you want them to be doing?
KWONG: Yeah.
CARLSON: Yeah.
KWONG: I mean, that kind of inner speech, like, spontaneous inner speech, sounds like birding. You-- scientists have to patiently wait and see if a bird shows up?
CARLSON: But the bird is own brain. [LAUGHS]
FERNYHOUGH: I love it. Yeah, exactly.
CARLSON: I mean, OK. So you also lead this project on voice hearing. So can you just tell us what voice hearing is and how it differs from spontaneous inner speech?
FERNYHOUGH: So we use the term "voice hearing" to describe the experience of hearing a voice when there's nobody around to have produced that voice. And we usually associate it with severe mental illness, so diagnoses like schizophrenia. What we've learned is that this experience happens to all sorts of people in all sorts of walks of life. Many, if not most, psychiatric disorders have voice hearing associated with them. But then there are, you know, a significant number of people who hear voices who are not distressed by them, who don't seek psychiatric help, who don't need psychiatric help because they're not distressed but find them useful, creative, guiding, spiritual, all these kinds of things. So the question of how that relates to inner speech, the theory is that when somebody hears a voice, what's actually happening is that they're producing some inner speech. So they're talking to themselves. But for some reason, that is not experienced as their own voice. It's experienced as coming from some sort of other entity or some sort of other place. And there's a good neuroscientific theory of why that works, and it goes back to those two parts of the brain, in fact, that bit, Broca, at the front, that bit, Wernicke, a bit further back. The idea is that usually, when you're speaking, that bit at the front sends a little internal message to that bit in the middle and says, you're about to speak. Don't pay too much attention to it. Don't kind of process this like you would process somebody else speaking, because it's just you. And the idea is that, in the case of voice hearing, that message doesn't get through in the same way. It's delayed, or it's degraded, or it doesn't happen at all.
CARLSON: Wow.
KWONG: So your brain can't tell you who's talking.
FERNYHOUGH: Yeah. Pretty much, yeah.
CARLSON: What's the difference between that and not having inner speech?
FERNYHOUGH: The work that Russ has done and the work that I've done with him has made it really obvious to me that some people don't use inner speech very much. Maybe some never use it at all. They do other things.
CARLSON: Yeah.
KWONG: Yeah.
FERNYHOUGH: They either use images. They use music. They use emotions. They use all the other stuff that's going on in head. It's also made it obvious to me that we're really bad at judging what's going on in our heads.
KWONG: But if speech is just a tool, do you think that an adult can develop their inner speech?
CARLSON: Ooh.
KWONG: Like, is it-- is it better to have one?
FERNYHOUGH: I'd like to celebrate the diversity of human minds. I think we are so different.
CARLSON: I think that's beautiful.
FERNYHOUGH: I think it's wonderful. There is this diversity, and we can celebrate that diversity. I wouldn't ever want to set out and say to people that they should improve their inner speech. But what I would say is that sometimes inner speech can have a negative side. And if your inner speech is bothering you, if it's excessively critical, you know, it can be wrapped up in all kinds of stuff that isn't particularly good for your mental health. And I'd say, if that's bothering you, there are maybe things that you can do to rethink it. And if people have any concerns or want to know more about hearing voices, we have a website called understandingvoices.com, where you'll find a whole bunch of different kinds of information about voice hearing, including how people make sense of voice hearing, what people do to seek help for voice hearing, and so on.
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KWONG: Charles Fernyhough, thank you so much for coming on Short Wave to talk about this. I think Rachel and I are a little speechless.
CARLSON: I'm speechless, yeah.
FERNYHOUGH: Thank you both.
KWONG: This episode was produced by none other than Rachel Carlson. She really does it all.
CARLSON: Thank you. It was edited by our showrunner, Rebecca Ramirez, and fact-checked by Tyler Jones.
KWONG: Kwesi Lee was the audio engineer, and Beth Donovan is our vice-president of podcasting. I'm Emily Kwong.
CARLSON: And I'm Rachel Carlson.
KWONG: Thanks for listening to Short Wave, from NPR.
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