It’s slightly strange that we talk to ourselves inside our own heads. It’s even stranger that we do it virtually the whole time we are awake. What’s strangest of all is that, despite coronavirus isolation making our internal chatter all the more apparent, we don’t often outwardly discuss the conversation in our heads.
Similarly, our scientific investigation of inner speech has made surprisingly little headway. Charles Fernyhough is a professor in the Department of Psychology at Durham University and author of The Voices Within, a book focusing on inner speech. He suggests that the first challenge is defining exactly what to call the noises we make inside our head: “A lot of people talk about the inner voice, which is a term I avoid, because it is very vague and fluffy and hard to pin down.”
Fernyhough says that people may associate the term “inner voice” with concepts like “gut feeling” or “moments of inspiration”, but what he and his team study is inner speech, a formal scientific term that involves the word-based conversations we have with ourselves inside our heads. Fernyhough has argued in his research that inner speech is a distinct type of auditory thinking, separate from, for example, imagining a siren going off. As we’ll see, inner speech’s developmental origins and unique characteristics separate it from these other between-our-ears phenomena.
Getting a grip on inner speech
Researchers in Fernyhough’s field have not chosen an easy area of study. Whilst behavioural neuroscientists can mimic fear responses in a mouse and neuroimaging researchers can look at highly-conserved reward pathways in non-human primates, studying inner speech in humans really requires human volunteers. These test subjects often aren’t particularly cooperative: “People find it very hard to reflect on their own inner speech. The reason it's had little attention, publicly, culturally, but also scientifically is that it's very hard to get a grip on one’s own inner speech,” says Fernyhough.
Fernyhough’s quest to understand inner speech began by observing outer speech at the beginning of the brain’s development. His research began in developmental psychology, studying how young children behaved when playing alone. Fernyhough noticed that his subjects would spend a lot of their time talking to themselves out loud. This seemed to fulfill a function beyond just annoying nearby working-from-home parents. “[The children] give a strong impression, and the research supports this, that they are doing it for a reason – they're doing it because it's helpful. They're getting some sort of cognitive benefit from it,” says Fernyhough.
As the children aged, this helpful out-loud speech gradually stopped. Had parents just asked them to keep quiet, or was there something more complicated involved? Fernyhough found an answer in the work of influential Soviet psychologist Lev Vygotsky. Vygotsky, Fernyhough tells me, believed that speech was something that began as a purely social instrument for communication between people that over the course of development became gradually internalized. This process of internalizing, Fernyhough says, gives us “tools for thinking” that benefit our development.
An evolutionary benefit to inner speech?
Not all aspects of our inner speech give obvious advantages to our behavior. Anyone who has anxiously spent hours internally processing worried thoughts about an exam, only to have no time to actually study for it, might wonder why such unhelpful examples of inner speech were not chopped out at an earlier point in evolution. Surely an early human would have been much “fitter” to their environment if they just threw a spear straight into a mammoth without ruminating on how they were going to extract the spear later, and whether this particular mammoth was going to be as delicious as the one they had caught last winter?
Jonny Smallwood, a professor in the Department of Psychology at the University of York, has made the study of one particularly aimless form of rumination, daydreaming, his own research niche. “Things like daydreaming, even though they might seem "purposeless” must be having some kind of quite important role in how we guide our lives,” says Smallwood.
But what is that role? Smallwood’s studies have looked at how people from different countries and cultures daydream. All his participants had one thing in common – they tended to think about the future. Smallwood reckons that this common finding hints at why internal states like daydreaming and inner speech have become so widespread. “One of the ways that the internal representation system can be selected for is because you can prepare for an interaction with another person and you can think about the kind of things that they might be happy or unhappy for you to say. Then, when you get into that circumstance, you're less likely to say the wrong thing, which might make the interaction smoother,” says Smallwood.
No such thing as a universal behavior
Internal processes like inner speech and daydreaming might give us an evolutionary advantage. But the most interesting thing about these processes isn’t their function, but their prevalence. Fernyhough has noted that inner speech, despite perhaps seeming to many people like the most innate behavior of all, is not ubiquitous. “You certainly find that private speech in children is pretty universal. You don't find many kids who are developing in a typical way that don't use private speech. But when it comes to adults, I came across people who clearly just weren't doing much inner speech,” says Fernyhough.
These internally silent volunteers instead commonly relied on imagery in their day-to-day thoughts, with pictures replacing words as their thinking tool of choice. “To my mind it says it's something that a lot of humans do because it's handy. But it's by no means an essential component of consciousness,” says Fernyhough. “We find different ways to get to the same outcome and I think that's one of the marvels of psychology.”
Variation in how we think isn’t limited to whether we use words or images. Sometimes, the very nature of our thinking can become disrupted. Fernyhough became acutely aware of this when he shared his developmental psychology findings with psychiatrist colleagues, who took his comments about inner speech to be referring to auditory hallucinations, or “hearing voices”.
Durham University's Palace Green Library hosted an exhibition titled Hearing Voices: suffering, inspiration and the everyday in 2016-17. Image credits from Durham exhibition: Andrew Cattermole Photography
These hallucinations are most commonly linked in popular culture to the mental health disorder schizophrenia. In reality, schizophrenia is a complex disorder, and auditory hallucinations are just part of an often varied range of symptoms. The idea that hearing voices is unique to schizophrenia is also misleading, suggests Fernyhough. “The experience of hearing voices is involved in all sorts of different psychiatric diagnoses, everything from post-traumatic stress disorder (PTSD) to eating disorders. It is also experienced by quite a small but significant number of people who are not mentally ill who hear voices quite regularly, but don't seek help for them because they're not troubled by them.”
Hearing the voice
Is there a fundamental difference between inner speech and auditory hallucinations? This question has been the target of a project Fernyhough is helping run at Durham, funded by the Wellcome Trust, called Hearing the Voice. The study is still ongoing, but some early conclusions are that the difference between these internal states is very simple. “The idea is that when somebody hears a voice, what they're actually doing is some inner speech, but for some reason, they don't recognize that they themselves made that bit of language in their heads,” says Fernyhough. “It’s experienced as coming from somewhere else or from someone else.”
What complicates this idea are the many types of both inner speech and auditory hallucinations. Fernyhough thinks that his theory will apply to some types of both experiences, but not all. Some hallucinations have acoustic properties, as if the speaker is in the room with you. Sometimes the voice has an accent or a timbre or a pitch. “It's very hard to pin down what it is that makes some people have an experience that feels alien, that is distressing, especially when some people have what seems to be the same experience, but don't find it distressing,” says Fernyhough. “I think the only thing you can really point to is that for some reason, that experience of hearing your voice doesn't feel like you. It comes from some other author or agency. And that's what can be, as you can imagine, very distressing.”
Inner speech inside a scanner
Bringing relief to that distress will require research into both "normal" and pathological forms of inner speech. To do that, psychologists rely on imaging techniques like fMRI and PET scanning. Nevertheless, the biggest advances in the field have been less to do with the hardware used and more about the way in which researchers get their participants to “do” inner speech.
At the beginning of these neuroimaging studies, researchers noted that when they asked their participants to engage in inner speech, areas of the brain’s basic language system began to light up. For most people, Fernyhough tells me, that means activation of the left hemisphere, particularly in an area at the front of the brain called Broca’s area.
As we talk, our respective Broca’s areas will be lighting up. Given the developmental connections between outward and inner speech, it might make sense that the same brain areas would be activated. But Fernyhough tells me these initial studies had some serious flaws.
“The problem is that when we do scanning experiments like this, what we tend to do is put people into a scanner, and we say to them, right, whilst you are lying there I want you to do some inner speech, and we tell them what inner speech to do,” says Fernyhough. Volunteers would be asked to say a particular phrase, such as “I like football,” in repetition whilst they lay inside the scanner.
Fernyhough points out that, except for the most single-minded fan, few people’s inner speech consists of repetitive statements about their love for sports. It’s more often complex and chopped up into smaller chunks of thought. To try and monitor this kind of natural inner speech, Fernyhough’s team took a different approach that made use of descriptive experience sampling, a technique where subjects are prompted to note down what their inner experience was just prior to the sounding of a beeper. The process is labor-intensive, as people often need to be coached to effectively capture the details of their inner experience.
Listen to a podcast by Hearing the Voice, in which we hear testimonies collected by Elisabeth Svanholmer (voice-hearer and mental health trainer) of how people have shared their experience of hearing voices.
Over time, Fernyhough believes the end result is much more valuable. “We were able to capture the moments in which they just happened to be doing inner speech spontaneously because it's what was in their head at that time. Not because we told them to,” says Fernyhough.
So was there any difference in brains doing this more “natural” inner speech as opposed to the repetitive, proscribed type? Fernyhough says there was a stark contrast. “Using descriptive experience sampling, we got a totally different pattern of brain activations. We found activations much further back in the brain, in areas that you would associate with speech perception and understanding, not speech production.” Whilst the findings need to be replicated, Fernyhough believes that if people’s brains act differently depending on whether they perform tasks spontaneously or in response to instruction, there could be ramifications for all kinds of imaging-based neuroscience.
These fundamental findings about the nature of our inner experience will only be expanded upon if neuroscience makes changes to how experiments are conducted, says Fernyhough. These changes in practice will also need to be at a fundamental level. “We've got fantastic machines and software for telling us what's going on in a particular cluster of neurons at a particular moment. We're not very good at the other thing, which is asking people about their experience, of getting at the subjective quality of experience. We really have to raise our game on that,” says Fernyhough.
Going forward, Fernyhough will try and bring this alternative focus to the analysis of voices as part of Hearing the Voice. Fernyhough thinks that exploring the vast range of different types of voices people hear in health and disease will raise questions not only about the brain, but about the nature of language and the mind itself. Exploring these differences could be brain research’s greatest challenge yet. But it’s a challenge that Fernyhough, at least, relishes: “So many people in psychology and cognitive science are kind of looking for the thing that makes us all the same. And I think that's a mistaken enterprise a lot of the time. I think we are so different in so many ways, in fascinating ways. And I think our minds are just one way in which we are very, very different. “
Worried about hearing voices? Visit the resources at Understanding Voices to get more information.