anendophasi

The phenomenon of anendophasi, the absence of an inner verbal monologue offers an interesting perspective in discussions about the nature of mind and consciousness. Some people report that they rarely or never experience thoughts in the form of an internal voice, yet they are still able to reason, plan, make decisions, and understand complex ideas. Their thinking often occurs through abstract concepts, visual imagery, or non-verbal intuition rather than words.
This variation is significant because it suggests that there is no single, uniform structure to conscious thought. If human cognition were produced by a single immaterial “soul” operating in the same way across individuals, one might expect mental experiences to be broadly similar. Instead, the diversity of internal experiences some people thinking primarily in words, others in images, and some with little or no inner narration appears to correlate with differences in cognitive style and likely with differences in brain organization.
For that reason, anendophasia can be seen as consistent with a materialist interpretation of the mind, where mental phenomena emerge from physical processes in the brain. The variability in how people experience their own thinking suggests that conscious thought is not a single fixed process but rather a set of cognitive strategies implemented by neural systems.

likely with differences in brain organization.

Nedergård & Lupyan, 2024, have found that individuals reporting low levels of inner speech (anendophasia) perform significantly worse on verbal working memory tasks and in rhyme judgments compared to those with high levels of inner speech.

I had mentioned this area before when I reported that I noticed that the inner voice changed to German about 2 years after I moved to Germany from the USA. I also began dreaming in German at that time. There was no longer a translation happening when Germans spoke to me. So it is also a flexible illusion of the mind.

I realized at that point in time that there is no language to thoughts, and no actual inner voice speaking any specific language. It is a structural or placeholder event we learn to use to function in society, and to organize and remember. But thoughts and feelings have no actual language, and thus no inner voice speaking any specific language. To me, it is learned, and not a natural human brain function that has to exist for our consciousness to function.

It is also interesting that...

Between ages 4-6, both brain hemispheres process language; by ages 7-9, this, specializes to the left hemisphere, making, language processing more fixed.

This window is also the critical cutoff period for grammar.
 
How this applies to the inner voice would be an interesting area to look into.

This variation is significant because it suggests that there is no single, uniform structure to conscious thought. If human cognition were produced by a single immaterial “soul” operating in the same way across individuals, one might expect mental experiences to be broadly similar...

Why? There are material heath conditions with no clear, detectable effect on the body; one might expect those people to have normal functions. Assuming an immaterial element or root to consciousness, how could you rule out variations like this?