Inner speech is not a universal experience.

The variability of inner speech suggests that thinking does not rely on a single format.

Lack of inner speech is sometimes referred to as anendophasia.

Studying internal experiences remains methodologically challenging due to reliance on self-report.

For many people, thinking comes with a voice. An internal stream of words narrates our day: planning dinner, rehearsing conversations, reflecting on decisions. This phenomenon (commonly referred to as inner speech) feels so natural that it is often assumed to be universal. It is typically described as a kind of internalized language, experienced through auditory imagery, often resembling one’s own voice, as if we are silently speaking to ourselves.

A Growing Catalogue of "Unusual" Experiences

Over the past decade, there has been a noticeable rise in discussions around what are often framed as unusual perceptual conditions. Much of this attention can be traced back to earlier interest in synesthesia, where sensory modalities blend in unexpected ways. From there, the conversation expanded to include aphantasia (the absence of visual imagery) and its counterparts, where individuals report extremely vivid mental images. These discussions opened the door to a broader exploration of internal experience: What does it actually feel like to think?

As interest grew, so did recognition of variability. Some people can vividly picture scenes, replay music in their minds, or simulate tactile sensations. Others report little to none of this. And increasingly, it seems that these differences are not isolated to a single sensory modality. More recently, the idea of lacking inner speech (sometimes referred to as anendophasia) has rapidly entered public and academic discourse, appearing in outlets such as The Guardian and Scientific American. Almost overnight, people began asking each other, "Do you hear a voice when you think?" "Is it really a “voice,” or something else entirely?". What emerged was not consensus, but diversity. Some people report a constant internal monologue. Others experience more fragmented or situational inner speech. And some suggest they may not experience it at all.

In research exploring these experiences is challenging. When participants are asked to “play” a song in their mind, or to imagine the texture of tree bark, responses vary widely. Some describe vivid, almost percept-like experiences. Others report faint impressions. And some report nothing at all. This raises an intriguing possibility - our internal experiences may not be uniformly distributed across senses. Instead, they may be selectively accessible, with some modalities more “tuned” than others. For one person, auditory imagery may be rich and detailed, while visual imagery is absent. For another, the opposite may be true.

From a cognitive science perspective, variability in perception is not new. However, phenomena like aphantasia or lack of inner speech highlight a fundamental methodological challenge of how we study these experiences that are inherently private. Much of the current research relies on self-report measures - asking individuals to describe what happens in their minds. But this introduces a critical ambiguity. Even carefully designed tools struggle to disentangle all the possibilities.

There is growing interest in complementing self-report with behavioural tasks and neuroimaging approaches. These methods attempt to provide more objective insights into internal processes. Yet, capturing subjective experience with objective measures remains one of the most persistent challenges in the field.

The debate around inner speech touches on something deeper than measurement. It raises a fundamental question of how much access do we truly have to our own cognitive processes? We tend to assume that our thoughts are transparent to us, that we can observe and describe them accurately. But this assumption may not hold. Introspection is not a direct window into the mind. It is itself a cognitive process—one that may be incomplete, biased, or shaped by language and expectation. This complicates everything: the way we describe our experiences, the way we compare them to others, and the way we build scientific models of cognition. If we try to imagine another person’s internal world based purely on verbal description, we encounter immediate constraints. Words can approximate experience, but rarely capture it fully.

This is where alternative approaches may offer new possibilities. Tools such as virtual reality, drawing, and visualization, interactive or 3D representations could allow individuals to externalize aspects of their internal experience in ways that are more direct, more embodied, and potentially more comparable. Rather than describing experience, we might begin to show it. The increasing attention to conditions like aphantasia and lack of inner speech suggests that we are only beginning to map the diversity of human cognition. These are not simply curiosities. They challenge core assumptions that perception is uniform, that thought follows a standard format, that introspection is reliable. Instead, they point toward a more complex reality. There may be many ways to think, imagine, and experience the world. And perhaps more importantly, there may be aspects of our own minds that remain inaccessible, even to us.

As research continues, new variations will likely emerge, raising further questions about what we consider typical, measurable, or even understandable. Rather than closing the gap in our knowledge, this line of inquiry may continue to expand it. And that, perhaps, is what makes it so compelling.

Nedergaard, J. S., & Lupyan, G. (2024). Not everybody has an inner voice: Behavioral consequences of anendophasia. Psychological Science, 35(7), 780-797. https://doi.org/10.1177/0956797624124300

Lind, A. (2025). Are there really people with no inner voice? Commentary on Nedergaard and Lupyan (2024). Psychological Science, 36(9), 765-767. https://doi.org/10.1177/09567976251335583

Thomas, C. S. Phenomenal Access Dissociation: Blindsight, Aphantasia, and the Structural Unity of Identity Without Phenomenal Channel. https://philpapers.org/rec/THOPAD-5

Butler, J. (2013). The Internal Monologue. In Rethinking Introspection: A Pluralist Approach to the First-Person Perspective (pp. 119-147). London: Palgrave Macmillan UK. https://link.springer.com/chapter/10.1057/9781137280381_8

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