Subvocalization

What it is

Internal speech typically made while reading or imagination is called Subvocalization (~ silent speech). It is a natural process while reading or imagination and provides the sound of the word as it is read [1, 2, 21]. It helps the mind access the meaning of the content while reading. It facilitates comprehension and memory-making while potentially reducing cognitive burden [3]. Edfelt believed that it is a developmental activity that reinforces learning and should not be disrupted during development. 

Subvocalization is the only mental activity that generates considerable but attenuated movement in the larynx [2]. It occurs through undetectable (to the reader) and minuscule movements of the larynx and other muscles involved in Speech articulation [3]. It involves bilateral activation in predominantly the left frontal lobe [5].

Role of Subvocalization in:  

A. Memory Processes:

1. Short-term memory formation through Alan Baddeley and Graham Hitch's Phonological loop proposal. 

This loop is "responsible for the temporary storage of speech-like information" [4,6]. It comprises of a non-dependent interaction [7] between: 

(i) A short-term accessible and malleable store in which memory is represented phonologically 

AND

(ii) A rehearsal process that preserves and refreshes the material by re-enacting it and re-presenting it to short-term storage. Subvocalization is a major component of this rehearsal [4]. It is controlled by top-down processing;[5] is conceptually driven, and relies on information already in memory [20] 

2. Working memory

Working memory span size ∝ rate of subvocalization. The time needed to subvocalize the number of items comprising a span is generally constant [8].

3. Encoding [10, 11, 12, 13]

Subvocalization appears to facilitate the translation of visual linguistic information into acoustic information [12, 14] and vice versa. Subvocalization interference impedes reading comprehension but not listening comprehension.

Activity	Subvocalization	Encoding (conversion)
See-say condition (one sees a word and is asked to say it)	Occurs	Visual linguistic information into acoustic information
Hear-write condition (when one hears a word and is asked to write it)	Occurs	Acoustic information into visual information
See-write condition (When one is asked to see a word and then write it)	Does not occur	Encoding is not required in the same sensory domain. Directly enters short-term memory
Hear-say condition (hear a word and then say it)	Does not occur	Encoding is not required in the same sensory domain. Directly enters short-term memory

B. Reading comprehension

Subvocalization's involvement in reading comprehension depends on task complexity. Although, typically it is an inherent part of reading and understanding a word; in some cases, it may not be involved at all. 

C. Auditory imagery

Intons-Peterson (1992) defines auditory imagery as "the introspective persistence of an auditory experience, including one constructed from components drawn from long-term memory, in the absence of direct sensory instigation of that experience." It is often but not necessarily influenced by subvocalization, [15] and has ties to the rehearsal process of working memory [4].

D. Role in Speech

Depending on the intensity of laryngeal muscle movement during speech, individuals can either be low or high vocalizers [16].

Clinical application

1. Individuals who stutter have a slower rate of subvocal articulation [9] and demonstrate a short-term reproduction of serial material slower than their counterparts [10].

2. Individuals suffering from schizophrenia and experiencing auditory hallucinations could show the result of over-activation of the muscles in the larynx. Electromyography demonstrated greater laryngeal muscle activation (though not easily detected and needs to be measured on a wider range) before auditory hallucinations occurred and hence are considered subvocalization [17]. 

3. Reducing subvocalization (~subvocalization interference): Remediation may be appropriate when conscious subvocalization significantly limits the rate of  reading simple materials [22]. 

• Suppression training: Here an individual is shown their own Electromyography recordings while attempting to decrease the movement of the articulatory muscles [13]. These recordings help individuals to monitor and ideally reduce subvocalization [13].
• Counting[18,19]
• Chewing [12] 
• Locking one's jaw while placing the tongue on the roof of one's mouth [12]

A major portion of the above content was mostly derived from the Wikipedia article:
Subvocalization. (2024, May 4). In Wikipedia. https://en.wikipedia.org/wiki/Subvocalization.
Other references are as follows

References: 

1. Carver, R. P. (1990) Reading Rate: A Comprehensive Review of Research and Theory (1990).
2. Cleland, D. L., Davies, W. C and T. C. 1963. Research in Reading. The Reading Teacher, 16(4), 224-228.
3. Rayner, Keith and Pollatsek, Alexander (1994) The Psychology of Reading.
4. Smith, J. D., Wilson, M., & Reisberg, D. (1995). The role of subvocalization in auditory imagery. Neuropsychologia, 33(11), 1433-1454.
5. Girbau, D. (2007). A Neurocognitive Approach to the Study of Private Speech. The Spanish Journal of Psychology, 10(1), 41-51.
6. Baddeley, A., Eysenck, M. W. & Anderson, M. C. (2009). Memory. New York, NY: Psychology Press.
7. Hubbard, T.L. (2010). Auditory imagery: empirical findings. Psychological Bulletin, 136(2), 302-329.
8. Standing, L., Bond, B., Smith, P., Isley, C. (1980). Is the immediate memory span determined by subvocalization rate? British Journal of Psychology, 71(4), 535-539.
9. Bosshardt, H. (1990). Subvocalization and reading rate differences between stuttering and nonstuttering children and adults. Journal of Speech and Hearing Research, 3”, 776-785.
10. Bosshardt, H. (1993). Differences between stutterers and nonstutterers short-term recall and recognition performance.”Journal of Speech & Hearing Research, 36(2)”, 286-293.
11. Locke, J., & Fehr, F. (1972). Subvocalization of Heard or Seen Words Prior to Spoken or Written Recall. The American Journal of Psychology, 8(1), 63-68. Levy, B. A. (1971). Role of Articulation in Auditory and Visual Short-Term Memory. Journal of Verbal Learning and Verbal Behavior, 10, 123-132
12. Eiter, B., & Inhoff, A. (2010). Visual Word Recognition During Reading by Subvocal Articulation. Journal of Experimental Psychology, 35(2), 457-470.
13. Cole, R. A., & Young, M. (1975). Effect of subvocalization on memory for speech sounds. Journal of Experimental Psychology: Human Learning and Memory, 1(6), 772-779.
14. Levy, B. A. (1971). Role of Articulation in Auditory and Visual Short-Term Memory. Journal of Verbal Learning and Verbal Behavior, 10, 123-132.
15. Hubbard, T.L. (2010). Auditory imagery: empirical findings. Psychological Bulletin, 136(2), 302-329.
16. Aarons, L. (1971). Subvocalization: Aural and emg feedback in reading. ‘’Perceptual and Motor Skills’’, ‘’33’’(1), 271-306.
17. Green, M. F., & Kinsbourne, M. (1990). Subvocal activity and auditory hallucinations: Clues for behavioral treatments?. Schizophrenia Bulletin, 16(4), 617-625.
18. Daneman, M., & Newson, M. (1992). Assessing the Importance of Subvocalization in Normal Silent Reading. Reading and Writing: An Interdisciplinary Journal, 4, 55-77
19. Slowiaczek, M., & Clifton, C. (1980). Subvocalization and reading for meaning. Journal of Verbal Learning and Verbal Behavior, 19.5, 573-582.
20. Klob, B. & Whishaw, I.Q. (2009). ‘’Fundamentals of Human Neuropsychology’’ (6th ed.). New York, NY: Worth Publishers.
21. Bruder, C., & Wöllner, C. (2021). Subvocalization in singers: Laryngoscopy and surface EMG effects when imagining and listening to song and text. Psychology of Music, 49(3), 567-580. https://doi.org/10.1177/0305735619883681.
22. Cloer, Carl T. Jr. “Subvocalization-Asset, Liability, or Both?” Yearbook of National Reading Conference 26, 209-213. 1977 URL.