This has always fascinated me
I have a friend that is hearing impaired, and frequently signs unconsciously, as if "muttering aloud" to herself. I always was curious if the though process is actually complete without a sort of verbalization.
This was interesting; it's specifically about creative thought process:
"Part II: Special Aspects of Creative Thought
2.1. Speech, language, and thought
Speech progresses rapidly, orderly, and sometimes quite creatively with no preparation in thought. Apparently, speech is the verbalized thought process itself (with speech slowing down the thought process or with speech not totally following the thought's associative complexity). The length of words and the complexities of grammar are added and handled in the brain's language centers. This implies that silent, "practical" thought (the type of thought discussed in this article) occurs mostly without verbalization, as an associative sequence of images (visual, tonal or otherwise) except where visual or tonal word images are being pursued. On the other hand, words are originally tonal images and only as writing was invented also became visual images.
Polyglot individuals can think in several languages at will. This indicates that the base of the thought is not in the words but in non-verbal associations behind them. Also, the speech centers (Wernicke's and Broca's Areas) are very small and the frontal lobes very large, indicating that thought occurs non-verbally with translation into verbal mode as needed (into any one of the different languages a person happens to know).
Time spent writing, with the on-going conscious effort of converting conscious thought into the flow of language, leads to continuation in verbalized thought (more so in philosophical work than in "practical" thought). One can almost hear the inner voice.
If somebody presents an argument in debate, the answer might be forthcoming instantly, while the associative thought process provides subsequently an acceptable explanation of its logic or validity and verbalizes it. This indicates subconscious interim thought sequences.
A surprising amount of idea creativity occurs during speech and writing. There may be different reasons for this effect, better targeting of thought being one. The verbalization itself may be another reason leading to associations by way of the used verbal concepts not available in silent (not verbalized, only image-based) thought. This corresponds to the crossing of associative paths mentioned earlier as a mechanism for surprise "ideas". The need to explain something better or more slowly and thoroughly may be another reason.
One can reasonably assume that deaf and blind people, using some visual or tactile sign language for communication, can reason equally well as fully capable people. Communication of thought can use a variety of sensory stimuli and codes, as any of them can be memorized. Whether the stored sensory image used in communication or an underlying, more reality-related image is used for thought may well be inconsequential if both are joined associatively.
The speech center (Broca's Area) is located in the left temporal lobe. There is no indication that thought is substantially impaired when this area is damaged. Also, the right side of the brain continues to function normally even when the connection to the left side, where Broca's Area is located, is interrupted (as in commissurotomy).
2.2. Encounters changing thought
Following the concept presented in this article, the brain, when awake (and possibly also when asleep), continuously goes through endless associative thought sequences, mostly subconsciously, becoming conscious only as certain intensity levels are reached. The associative sequences change abruptly when unrelated sensory inputs reach a high intensity level or trigger thoughts of high intensity relative to their positive or negative consequences (as in conditioned responses). (Example: A worker on an assembly line may be in a dozing state of mind. However, when his machine malfunctions, the resulting problem will bring him to a high attention level or focusing of his thought on the problem).
Similar effects on thought sequences result from encounters in the course of daily life or the appearance of images due to sensory input."
The full article or essay is at
this site