Does everyone have an inner monologue?

The "little voice in your head" can be your worst critic and greatest supporter. It's been known to help with directions, give advice, rehearse tough conversations and even remind you to put pesto on the grocery list. 

But does everyone have an inner monologue? For a long time, it was assumed that an inner voice was simply part of being human. But it turns out, that's not the case — not everyone processes life in words and sentences. 

"By inner monologue, we mean that we can have private speech that's addressed to ourselves and that is carried out without any articulation or sound," said Hélène Lœvenbruck, a senior neurolinguistics researcher and head of the language team in the Psychology and NeuroCognition Laboratory at CNRS, the national French research institute. 

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With true inner speech, you almost "hear" your inner voice, she told Live Science. You're aware of its tone and intonation. For example, the voice can "sound" angry or worried. Research has shown that children as young as 5 to 7 can utilize an inner voice, and some studies suggest kids may use some form of inner phonetics as early as 18 to 21 months of age.

Lœvenbruck's research looks at inner monologues in three dimensions, according to a 2019 study she and colleagues published in the journal Frontiers in Psychology. The first is dialogality. Humans can have such complex inner speech, there's debate about whether it's accurate to call all inner speech a monologue. So the first dimension measures whether you're thinking in a monologue or a dialogue. A monologue happens when you think to yourself something like, "I need to buy bread." But other times, when you are reasoning, you might entertain and engage several points of view — like a conversation, a dialogue. 

The second dimension is condensation, a measure of how verbose your inner speech is. Sometimes you think in words or fragments. But other times, like when you're preparing for a conversation or presentation, you're likely thinking in whole sentences and paragraphs. 

The third dimension is intentionality. Are you engaging in inner speech on purpose? For reasons we don't know, sometimes inner speech can just come to you or drift to entirely random and seemingly disconnected topics. 

But a long-time confounder in studying inner speech was the fact that, in studies, people expressed their thoughts in words, Lœvenbruck said, even if they weren't exactly thinking in words. 

This long-held assumption that all people rely on an inner voice was first challenged in the late 1990s, in large part by research led by Russell Hurlburt, a psychologist at the University of Nevada, Las Vegas. Hurlburt studied participants' inner speech by asking them to wear a beeper. Whenever the device beeped, they had to write down what they were thinking or experiencing in their mind just before the sound. At the end of the day, they met with a researcher to go over their responses.

Perhaps the participant wrote down, "I need to buy some bread." The researcher would then ask if that's what they actually thought. "Or did you think 'bread'? Or were you hungry, or was there a sensation in your stomach?" Lœvenbruck explained. With each meeting with the researcher, participants got better at articulating their true thoughts, she said. Eventually, this methodology revealed that some people had inner speech every time the device beeped, almost like "there's a radio in their head," Lœvenbruck said. But others had less inner speech than usual, and some didn't have inner speech at all. They experienced images, sensations and emotions, but not a voice or words.

The lack of an inner monologue has been linked to a condition called aphantasia — sometimes called "blindness of the mind's eye." People who experience aphantasia don't experience visualizations in their mind; they can't mentally picture their bedroom or their mother's face. Many times, those who don't experience visualizations don't experience clear inner speech, either, Lœvenbruck noted. You can participate in Lœvenbruck's research on aphantasia and inner speech via a survey starting this month.

Aphantasia and the lack of an inner voice aren't necessarily bad. But a better understanding of inner speech and the wide array of thought processes people experience could be especially important "for learning methods and education in general," Lœvenbruck said. Up until now, the types of inner speech and experiences children can have, and the resources they may need to learn, have likely been vastly underestimated, she said. 

Editor's note: Updated on June 15, 2021, at 2:38 p.m. ET to fix Hélène Lœvenbruck's title.

Originally published on Live Science.