The last great mystery of the mind: are you one of those people who hear a voice in their head?

Sara was 29 years old when she discovered that some people heard voices in their minds. “In a conversation with friends, someone mentioned something they had read on Twitter about [a person] whose brain was constantly talking to them. It surprised me: it seemed like an absolutely disturbing thing that I would never tolerate.”

For many, inner speech is a presence as constant and familiar as the beating of the heart, or the growls of hunger in the stomach at certain times of the day. But there are those who claim that they’ve never experienced it.

“Instead of words, it’s more like a succession of images and sensations that are organized in my head,” Sara explains, discussing how she perceives her flow of thought. “If I plan my day, for example, I see details like a subway line, its specific color, the place I’m going, or even the face of the person I’m going to meet. Maybe, if I’m in a stressful situation, I have to force an internal narration… usually out loud. But it happens very rarely.”

The revelation about the absence of an inner voice in some people went viral in 2020. A user named @KylePlantEmoji wrote on X (formerly Twitter): “Fun fact: some people have an internal narrative and some don’t. As in, some people’s thoughts are like sentences they ‘hear,’ and some people just have abstract non-verbal thoughts and have to consciously verbalize them. And most people aren’t aware of the other type of person.”

The post generated thousands of responses. Many people began to question the nature of their own inner thinking. A young woman interviewed by The New York Post following this debate confessed that she was unaware of the existence of internal dialogue – that is, until she saw the tweet. “If I talk to myself, I do it all out loud,” she explained. “If I strive to put my thoughts into words, then they manifest as such. But otherwise, it’s abstract, like a cloud of feelings and thoughts without defined, conscious words.”

Is it possible not to have an inner voice? “Yes, it’s possible,” confirms Russell T. Hurlburt, a pioneering psychologist in the study of the inner voice and subjective experience. He’s been researching this issue for 50 years. He tells EL PAÍS that, when he began, “the world was a very behavioral place,” in which there were also no mobile phones. Therefore, he had to invent a device that could be carried throughout the day by those who agreed to participate in an experiment aimed at exploring what was happening inside their minds. “Everyone wants to know what’s going on inside other people’s heads. It’s like when you turn on the television and ask a player what he was thinking just before scoring the goal that led his team to victory. I realized that question wasn’t being asked correctly, or answered adequately.”

The scientific method he invented is called Descriptive Experience Sampling. Participants wear a type of pager that beeps randomly throughout the day. Upon hearing it, they write down what’s happening in their mind at that specific moment. Later, in consultation, they share their records with the psychologist and analyze which internal phenomena predominate in their mind. “At first, it’s very difficult for them to detail their internal experience at an exact moment. They describe reflections from minutes ago, or the reasons behind those thoughts. It’s an exercise that, like any other discipline, requires practice.”

Over the years, this scientist – who still works as a researcher at the University of Nevada – has discovered several things. Firstly, that people maintained an internal dialogue for 26% of the time they were sampled. “Some don’t have it at any time…and others [maintain an internal dialogue] almost all the time,” he points out. Secondly, people don’t really know what’s going on in their minds. “There are individuals who claim to have extensive internal dialogue, when, in reality, they have little or none – and vice versa,” he explains. “Understanding what really happens in our mind – without having explored it before – is as complex as trying to describe a dream.”

Studies on how people think and how we experience our own thinking have revealed that mental processes can be very diverse. Some people have a strong, constant internal monologue, while others think more visually or abstractly. In 2017, a study from NeuroImage shed light on how, even when we’re thinking in words, our minds may also be generating visual images. Another study measured the number of people who heard an internal voice while reading: it was 80%, with 35% of participants always hearing an internal voice and 45% hearing one often. Furthermore, only some participants reported being able to control all aspects of this internal voice, such as pitch or speed.

Berta, 28, claims to have conversations with herself every day. “A large part of my internal monologue consists of rehearsing or anticipating hypothetical conversations. Like, when I’m angry with someone and I think about how upset I would be with them,” she explains. Your inner voice helps you make decisions or plan the day. At other moments, it manifests itself in the form of words that are repeated obsessively. “For example, there was a period when I couldn’t stop thinking about [one particular word], which was quite disturbing. I think I heard it while watching Survivor and it got stuck in my head.”

Inner speech isn’t governed by many of the rules of verbal language. It’s generated much faster, as it doesn’t depend on the rhythm necessary to use the tongue, lips and larynx. According to one study, internal monologues occur at an average speed of 4,000 words per minute: 10 times faster than spoken language. In addition, internal monologues are usually more concise, as we don’t need to formulate complete sentences when communicating with ourselves (since we already understand our own intentions).

Our inner voice normally replicates the timbre and tone that one identifies with, although it can also appear with voices different from ours. An article published in The Guardian gave the example of a woman who claimed to have no idea why a belligerent couple had taken over her inner voice: “I have no idea where this came from. They engage in passionate discussions.”

Ethan Kroos, a neuroscientist, maintains that, in reality, we all have an inner voice. “To check this, just ask someone to repeat a phone number in their mind. In my experience, everyone can do it,” he notes, over a video call with EL PAÍS. This ability represents one of the most fundamental neural functions in humans. “It’s part of the verbal working memory system, essential for our cognitive functioning. By silently repeating names or phrases, we’re activating that inner voice – something we all feel at different levels.”

Kroos considers it essential to distinguish between the internal voice that’s used to hold active information in the mind for a short period of time (like someone repeating a password or phone number, so as not to forget it) and the dialogue that people sometimes have with themselves. “There are those who use it to rehearse or plan what they’ll say, for example, in an interview or in a presentation. I’ve met people who tell me that they don’t have an internal voice – and my conclusion is that what they’re referring to is just that they don’t use the internal voice in this specific way.”

Due to special circumstances – such as that of the woman whose head had been conquered by a noisy couple – the internal voice can come to be perceived as torment. “The problem arises when this voice becomes obsessed with negative thoughts and ruminations. Like when you try to concentrate on reading a book after having an argument with your partner,” Kroos explains. “Although it’s possible to learn to control it, we’re rarely taught from a young age how to do it… many never address it.” And, while we live in an era full of distractions and stimuli, it’s not clear that our internal dialogue is more chaotic than in the past. “In prehistory, we fought for food every day and in the Middle Ages, they could leave you for dead in the street: these stressful situations also cause the inner voice to activate.”

In his book, he emphasizes the need to manage our inner voice, so as to maintain emotional well-being. He argues that this voice – if left unchecked – can aggravate stress and anxiety. To achieve this, he proposes techniques such as distancing, which involves observing oneself from an external perspective. You can, for instance, establish rituals to gain control, surround yourself with environments and people that broaden your perspective, moderate exposure to negative stimuli, or surround yourself with the natural environment. Additionally, he suggests tools – such as writing and meditation – as effective means of channeling and mastering inner thoughts.

The monologue with oneself has been interpreted in different ways, depending on cultural and social context. In the Platonic dialogues, Socrates refers to a daimon – an internal voice that acts as a moral guide. During the Middle Ages, this dialogue could be considered divine inspiration… or demonic temptation. Both Christian mystics and Chinese Buddhists have expressed frustration at the insistent interruption of their inner voices during their moments of prayer or meditation.

Hulburt – the researcher who developed a technique for scrutinizing the human mind – points out that these ancient traditions invested more effort than us in understanding and managing internal dialogue. When applying his method to experienced meditators, he observed notable differences: “Their thinking is primarily sensory.” Furthermore, Hulburt recognizes the influence of traditional meditative gong on his scientific method. “Some Buddhists have told me that my technique could be a more efficient way to teach people to control their mental flow and focus on the present. My device acts like a gong, with the advantage of being portable.”

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