New Psychological Research Reveals That Not Everyone Has An 'Inner Voice'

Researchers Johanne Nedergaard and Gary Lupyan explain what it's like to not experience 'inner speech.'

By Mark Travers, Ph.D. | July 12, 2024

A new study published in Psychological Science has revealed a novel psychological phenomenon known as "anendophasia." The study challenges the common assumption that inner speech—the experience of thinking in a natural language—is a universal human experience. Instead, it presents evidence that the frequency and presence of inner speech vary significantly among adults.

I recently spoke to lead author Johanne Nedergaard of the University of Copenhagen to talk about inner speech and its effects on cognitive processes. Here's a summary of our conversation.

What motivated you to explore the topic of inner speech and its effects on cognitive processes?

From a scientific point of view, I have always been fascinated by the relationship between language and cognition—how the language we speak influences what we think, whether language is necessary for certain kinds of thought, whether language can generally be seen as a mirror of the mind, etc.

Questions such as these are extremely difficult to test empirically, so I decided to take a slightly more concrete approach to studying inner speech. Focusing on how people talk to themselves and what effects that has on things like behavior, motivation and problem-solving allows both the use of empirical methods and provides a way of trying to answer the more abstract questions of what role language plays in our cognition.

How would you define 'inner speech' in an individual, and what does the lack of inner speech indicate?

I like the way Alderson-Day and Fernyhough (2015, p. 931) define inner speech: "Inner speech can be defined as the subjective experience of language in the absence of overt and audible articulation."

Note that this way of defining it means that you do not necessarily need to "hear" an inner voice, although this is usually what people report—language is many things besides the sounds and movements associated with overt speech. For example, sign language users also report engaging in "inner signing," which is an entirely different modality but still language.

Research on inner speech generally has only recently started to take individual differences in experience seriously, so we still do not know what a lack of inner speech might indicate and might be related to (e.g., differences in development, relations with other types of neurodiversity, etc.)

In our recent study, however, my colleague Gary Lupyan and I found that people who reported experiencing little to no inner speech in their daily lives were worse at tasks that required recalling similar words in a specific order and making rhyme judgments.

This suggests that this group of people at least have trouble imagining speech sounds, which fits well with their reports of lacking inner speech. It still remains to be seen whether they still "think in language" without "hearing" it or simply think in an entirely different manner. There are many other self-reported differences that we plan to explore in future studies—for example, people who lack inner speech report simulating past and future conversations much less, which one could hypothesize might have consequences for social interactions.

In what ways does inner speech differ from speaking out loud or silent thinking, and how can people become more conscious of their inner dialogue?

For people who have a very clear experience of hearing an inner voice and make use of it very often in their daily lives, I suspect there is not much difference between speaking to yourself out loud and speaking to yourself internally.

People who lack inner speech often tell me that they externalize to do the same kinds of tasks that other people use their inner voice for—this could, for example, be practicing asking a question in a social setting or remembering a shopping list.

This externalization can be achieved by talking out loud or writing things down. In the study I mentioned above, people with less inner speech were also able to completely make up for the difference in performance in the memory and rhyme tasks if they named the items out loud.

I think the best way of becoming more conscious of your inner speech is to try sampling yourself for a few days. The way to do this is to set a timer to alert you at 5-6 random times during the day (for example, with an app) and note down what was going on in your inner experience at the moment the timer went off.

This way, you can better discover how much of the time you are talking to yourself versus, for example, engaging in visual imagery. And for the moments you were talking to yourself, it is easier to see whether your inner speech is constructive and helpful or not.

How does inner speech impact our memory, problem-solving skills and overall cognitive functioning? Are there practical strategies to enhance our inner speech for better outcomes?

There is quite a lot of evidence that inner speech generally helps memory, problem-solving skills, attentional focus, endurance and cognitive flexibility (i.e., switching between tasks when it is appropriate).

However, it can also have a negative impact. For example, trying to remember something that was very visually detailed verbally actually makes the memory less accurate. This is known as "verbal overshadowing." If you lose control of your inner speech, it can, of course, also have a negative impact—as we see with negative rumination in anxiety and depression.

Interventions targeting and trying to change inner speech are mostly known from sports psychology. Research in this field indicates that there are no universally "better" things to tell yourself to enhance performance.

Instead, the best way seems to be to become more aware of what you naturally say to yourself in different situations and try to come up with different statements that would be more helpful—tailored to you as an individual.