As you read this text, you can probably hear your inner voice narrating the words.

Inner speech — the silent production of words in one's mind — is a core aspect of our mental lives.

It is linked to a wide range of psychological functions, including reading, writing, planning, memory, self-motivation and problem-solving.

Even though researchers estimate that we spend at least half of our lives talking to ourselves, this can vary between people.

The issue took off on social media this week after the author of viral article wrote about his shock after discovering that some people don't have inner speech.

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Some people have an internal monologue that is constantly commenting on everything they do, whereas others produce only small snippets of inner speech here and there as they go about their day.

The manifestation of people's inner speech can also vary.

The most common type is motivational or evaluative inner speech, where inner speech is used to assess our own behaviour.

An example of this is when an athlete mentally prepares themselves for a big game (when they "psych" themselves up), or when they evaluate their performance after the match.

Another type is dialogic inner speech, which is the tendency to engage in a back-and-forth conversation with yourself.

This type of inner speech can be in full sentences or in an abbreviated form (because you already know the meaning of what you're saying), and can even involve saying something that you think someone else would say.

Inner speech, the silent production of words in the mind, is a core aspect of most people's mental lives. ( ABC Open contributor tassiescape )

Say what?

Does everybody have inner speech?

A study in 2011 gave beepers to 30 participants, and when the beeper went off, participants had to write down what was going on inside their head.

After several weeks of this, the researchers discovered that some participants experienced inner speech almost all of the time, some experienced it occasionally and others never experienced it at all.

Several other studies have asked participants to complete a questionnaire on their experience of inner speech. Even though the vast majority of respondents claim to have some form of inner speech, a minority do not.

These results prompt two questions.

First, what's going on inside the heads of people who don't have inner speech?

There are individual differences, of course, but some people think with images, concepts, and emotions.

And when asked "what are you thinking?", these people translate their non-verbal thoughts into words, which they then use to communicate with.

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Second, if inner speech is important for a wide range of psychological functions, how is it that people are able to survive without it?

This is an open question, but it is clear that people who don't have inner speech are capable of thriving in their personal and professional lives.

What's going on in the minds of those without inner speech?

So why don't some people have inner speech? Studies show that producing inner speech requires a network of brain activity spanning from the frontal lobe to auditory cortex, which is located near your ears.

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These networks are the same as those used when we speak aloud (which also requires motor cortex, because we need to move our tongue, lips, etc.).

One theory proposes that people who do not produce inner speech are unable to activate those networks without also activating their motor cortex.

Another theory is poor introspection, which refers to a person's ability to examine their own mental processes.

According to this theory, everyone produces inner speech, but some people are conscious of it whereas others are not.

Or maybe we're thinking about this the wrong way. Maybe it is possible that the absence of inner speech is the brain's default setting (do human infants, or animals, have inner speech?), and there might be something unusual about people who do have it.

Regardless, there might be a silver lining to not being able to produce inner speech.

For instance, inner speech might help us to solve problems, but it can also put us down, which can lead to the development of anxiety, depression, eating disorders, and many other forms of mental illness.

Some people say they do not have any inner speech while others experience an almost constant internal dialogue. ( Mohamad Hassan (Pixabay) )

Understanding the function and dysfunction of inner speech, as well as why some people have it and others don't, is an important area of psychological research.

Ultimately, this has the potential to unlock new industries, as well as revolutionise education and mental health.

Bradley N Jack is a researcher in the School of Psychology at the Australian National University.

