Why Do We Hear a Voice in Our Heads?

Yagmur Kara

8/21/20269 min read

Something strange is probably happening as you read this.

Your lips are not moving. Your vocal cords are not vibrating. No one in the room is reading these words aloud.

And yet, somehow, you can “hear” them.

Perhaps they sound like your own voice. Perhaps they do not sound like a voice at all, but you still sense the words being spoken. The same thing happens when you argue with yourself, rehearse an answer before a conversation, run through a list of things you need to do, or replay something someone said years ago.

All of it happens in silence.

So if there is no actual sound, what exactly is speaking inside your head?

And perhaps more strangely, who is listening?

Scientists generally call this experience inner speech: the experience of language in the mind without audible speech. The definition sounds simple enough, but it describes something surprisingly complex.

When we speak silently to ourselves, the brain does not appear to switch to an entirely separate system. Instead, it reuses some of the machinery involved in speaking aloud.

Brain imaging studies have found activity in several language-related regions when people silently think in words. One of them is the left inferior frontal gyrus, an area in the lower frontal part of the brain that contains regions closely involved in producing and organizing speech, including what is commonly known as Broca’s area. Parts of the temporal lobes, which contribute to processing speech and sound, may also become active, along with networks involved in planning and monitoring what we say.

There is no single “inner voice centre” in the brain. Inner speech seems to emerge from several systems working together.

In a sense, the brain begins preparing speech but stops before producing it aloud.

You can notice part of this experience for yourself. Say your name silently, then repeat it unusually slowly in your mind.

There is no physical sound. Still, you may sense the rhythm of the word, the length of its syllables or even certain qualities of your own voice.

Inner speech, then, is not merely an abstract idea. It is a genuine mental process connected, at least partly, to the systems we use to produce and perceive spoken language. But if inner and spoken language share some of the same machinery, how do we know that the voice belongs to us?

When you think, I need to wake up early tomorrow, why do you recognize the sentence as your own thought rather than a voice coming from somewhere in the room?

How the Brain Recognizes Its Own Actions

Part of the answer may lie in the brain’s ability to predict the consequences of its actions.

Whenever the brain sends a command to move the body, it may also produce a kind of internal copy of that command. Researchers use terms such as efference copy and corollary discharge to describe related parts of this process.

The terminology sounds complicated, but the basic idea is straightforward: when the brain causes an action, it can also predict what that action should feel or sound like.

This may help explain why it is so difficult to tickle yourself.

When someone else tickles you, the exact timing and pressure of the touch are not entirely predictable. When you try to do it yourself, your brain already knows where your hand is moving and what sensation it is likely to produce. Because the touch is expected, its effect is weakened.

Something similar happens when we speak.

Before the sound of your voice reaches your ears, your brain already has information about the sound it intends to produce. It therefore does not process your own voice as though it were a completely unexpected event coming from somewhere else.

Some researchers believe inner speech involves a related mechanism. The brain may generate a prediction alongside the silent words, helping it identify the experience as self produced.

Experiments have provided evidence for this possibility. In one study, participants silently produced a particular speech sound while hearing sounds through headphones. The brain’s response to an external sound became weaker when it occurred at the same moment and matched the sound the participant was producing internally. When either the timing or the content did not match, the same reduction was not observed.

This result suggests that inner speech may carry surprisingly precise information. Rather than registering only that a verbal thought is happening, the brain may predict what the imagined sound should be and when it should occur.

This mechanism has also become part of research into a much more complicated experience: why a thought or voice may sometimes fail to feel self generated.

One hypothesis concerning auditory verbal hallucinations experiences of hearing speech when no external speaker is present is that differences in the systems used to identify self produced mental events may sometimes play a role. An internally generated verbal experience might not be recognized in the usual way and could therefore feel as though it came from another source.

This is only one proposed explanation. Auditory hallucinations are complex and cannot all be reduced to “misidentified inner speech.” Memory, emotion, expectation, perception and several other processes may be involved. Researchers still do not have a single explanation that accounts for every case.

Not Everyone Has a Constant Inner Monologue

People do not all experience inner speech in the same way.

It is easy to assume that other minds work like our own. If you talk to yourself throughout the day, you may imagine that everyone else does too. Research into everyday inner experience suggests otherwise.

One method used to study these differences is called Descriptive Experience Sampling, or DES. Participants carry a device that alerts them at random moments during the day. When it signals, they pay attention to whatever was happening in their mind immediately before the alert. Later, trained researchers interview them carefully about that specific moment.

The method is intended to capture ordinary mental experience before people have time to turn it into a general story about how they believe they usually think.

In one well known study, researchers collected ten randomly selected moments from each of 30 participants. Inner speech appeared in approximately 26 per cent of all the moments sampled.

That average, however, conceals enormous individual differences.

Some participants reported inner speech in many of their sampled moments. Others did not report it in any of them. Some seemed to have highly verbal inner lives, while others relied more on imagery, feelings, sensory awareness or other forms of thought.

The study was small and involved university students, so 26 per cent should not be treated as a universal measurement of how often the human mind speaks. Studying private experience is also extremely difficult. Results can change depending on how a question is asked, how inner speech is defined and whether people are describing a specific moment or estimating their usual experience.

What the research does show is that a constant internal narrator should not be treated as a universal human experience.

That does not mean people without frequent inner speech are not thinking. Thinking and thinking in words are not the same thing.

Picture a lemon.

Perhaps you saw a yellow fruit in your mind. Perhaps you imagined its sharp taste or the texture of its skin. Perhaps the word lemon appeared. Or perhaps none of those things happened, yet you still knew exactly what you were thinking about.

The mind is not made of language alone. Thought can involve visual images, emotions, bodily sensations and spatial impressions.

Researchers using DES have also documented what participants describe as unsymbolized thinking: having a specific thought without experiencing it in clear words, images or other recognizable symbols. Whether this should be treated as a distinct form of thought remains debated, partly because private mental experiences are so difficult to describe and measure.

Even so, people clearly differ in how their thoughts appear to them.

Two people may solve the same problem while experiencing entirely different things internally. One might silently tell themselves:

First I’ll do this, and then I’ll move on to that.

Another might picture each step. A third may experience no distinct voice or image, yet still know what needs to be done.

From the outside, all three appear to be thinking. Internally, the experience may be very different.

What Is Inner Speech For?

Inner speech probably does not have one single purpose.

Researchers have connected it to working memory, planning, problem solving, emotional regulation and the control of behaviour. Some of these connections are better established than others, and inner speech is not necessary for every kind of thought. Still, it appears to be a useful mental tool in many situations.

Working memory is the system that allows us to hold and use a limited amount of information for a short period. It helps you keep a phone number in mind long enough to type it, remember the beginning of a sentence while reaching the end, or follow several instructions in the correct order.

Inner speech can support this system through silent repetition.

If someone tells you a number and you keep repeating it in your mind, you are using verbal rehearsal to prevent the information from disappearing. If another task interrupts that repetition, remembering the number usually becomes more difficult.

Inner speech may also help us direct our attention and behaviour.

During a difficult task, you might tell yourself:

Slow down.

Finish this part first.

Check it one more time.

These short instructions can help keep a goal active. Before a stressful conversation, you may rehearse what you want to say. After making a mistake, you may use internal language to consider what should be done differently next time.

Seen this way, inner speech is not simply a narrator commenting endlessly on life. Sometimes it appears to function as one of the ways we guide our own attention and actions.

The same ability can, however, become unhelpful.

A conversation can be rehearsed so many times that preparation turns into anxiety. An old argument can be replayed without producing any new understanding. A useful warning can gradually become constant self criticism.

Inner speech may help us organize our thoughts, but it does not guarantee that those thoughts are accurate. A sentence does not become true simply because it appears in our own voice.

The Child Behind the Inner Voice

There may also be a developmental story behind the voice in our heads.

Listen to young children while they play or attempt something difficult and you may hear them narrating their actions aloud:

“Now this goes here.”

“No, that didn’t work.”

“I need the red one first.”

This behaviour is known as private speech. Unlike ordinary social speech, it is not primarily directed at another person. The child appears to be using language to guide their own actions.

Psychologist Lev Vygotsky proposed that this form of speech begins in social interaction. At first, adults use words to direct a child: Be careful. Put that here. Try again. Gradually, children begin using similar language to direct themselves.

As they grow older, this private speech may become quieter, more abbreviated and eventually internal. What was once spoken aloud becomes part of silent thought.

Modern research has not confirmed every detail of this developmental account, and inner speech is probably more varied than any single theory can explain. Even so, studies have found meaningful connections between children’s private speech, the difficulty of a task and their ability to regulate their own behaviour.

Children often speak to themselves more when a task becomes challenging. Adults sometimes do something similar. A person who usually thinks silently may begin muttering instructions while assembling furniture, searching for a lost object or trying to solve a complicated problem.

Private speech may not simply disappear as we grow older. In certain situations, it can return to an audible form when we need additional help directing ourselves.

If Vygotsky’s account is broadly correct, the silent narrator in your mind may have roots in the child you once were the child who worked through problems by speaking aloud.

It may also carry traces of other people.

The phrases used by parents, teachers and friends can become part of the language we later use with ourselves. This may be one reason the inner voice can sound encouraging at one moment and sharply critical at another. Not everything it says necessarily began with us, even if we now experience it in our own mind.

So Are We Really “Hearing” It?

Strictly speaking, we do not hear inner speech in the same way we hear a voice in the room.

Instead, the brain activates some of the systems used to plan speech, represent language and predict sound without completing the physical act of speaking. That activity can produce a subjective experience resembling a voice, even though the experience remains silent.

For some people, that voice may seem vivid and detailed. For others, inner speech is less like hearing and more like knowing that words are present. It may consist of complete sentences, compressed fragments, competing perspectives or words that seem to carry the tone of someone they know.

For others, it may occur only occasionally.

There is still much we do not understand. Scientists cannot directly enter another person’s conscious experience. They can measure brain activity, interrupt verbal rehearsal, collect reports and compare patterns, but inner speech remains private by its nature.

Perhaps the most interesting question, then, is not simply where the voice inside our heads comes from.

It is how different the inside of one mind may be from the inside of another.

From the outside, we all seem to be doing the same thing: thinking.

But what thinking feels like from within is something each of us knows through only one mind our own.

Sources and Further Reading