Speech production

Human vocal apparatus used to produce speech

Speech production is the process by which spoken words are selected to be produced, have their phonetics formulated and then finally are articulated by the motor system in the vocal apparatus. Speech production can be spontaneous such as when a person creates the words of a conversation, reaction such as when they name a picture or read aloud a written word, or a vocal imitation such as in speech repetition.

Speech production is not the same as language production since language can also be produced manually by signs.

Faculty

In ordinary fluent conversation people pronounce each second roughly four syllables, ten or twelve phonemes and two to three words out of a vocabulary that can contain 10 to 100 thousand words.^[1] Errors in speech production are relatively rare occurring at a rate of about once in every 900 words in spontaneous speech.^[2] Words that are commonly spoken or learned early in life or easily imagined are quicker to say than ones that are rarely said, learnt later in life or abstract.^[3][4]

Normally speech is created with pulmonary pressure provided by the lungs that generates sound by phonation in the glottis in the larynx that then is modified by the vocal tract into different vowels and consonants. However speech production can occur without the use of the lungs and glottis in alaryngeal speech by using the upper parts of the vocal trait. An example of such alaryngeal speech is Donald Duck talk.^[5]

The vocal production of speech is usually associated with the production of synchronized hand gestures that act to enhance the comprehensibility of what is being said.^[6]

Three stages

The production of spoken language involves three major levels of processing.^[1][7][8]

The first is the processes of conceptualization in which the intention to create speech links a desired concept to a particular spoken word to be expressed. Here the preverbal intended messages are formulated that specify the concepts to be verbally expressed. This is a competitive process in which an appropriate word is selected among a cohort of candidates.^[1][7][8]

The second stage is formulation in which the linguistic form required for that word's expression is created. This process involves such processes as the generation of a syntactic frame, and phonological encoding which specifies the phonetic form of the intended utterance. At this stage a lemma is picked that is the abstract form of a word that lacks any information about the sounds in it (and thus before the word can be pronounced). It contains information concerning only meaning and the relation of this word to others in the sentence.^[1][7][8]

The third stage is articulation which involves the retrieval of the particular motor phonetics of a word and the motor coordination of appropriate phonation and articulation by the lungs, glottis, larynx, tongue, lips, jaw, and other parts of the vocal apparatus.^[7]

Neuroscience

Speech production motor control in right handers depends mostly upon areas in the left cerebral hemisphere. These areas include the bilateral supplementary motor area, the left posterior inferior frontal gyrus, the left insula, the left Primary motor cortex and temporal cortex.^[9] There are also subcortical areas involved such as the basal ganglia and cerebellum.^[10][11] The cerebellum aids the sequencing of speech syllables into fast, smooth and rhythmically organized words and longer utterances.^[11]

Disorders

Speech production can be affected by several disorders:

• stuttering
• Lisp
• Speech sound disorder
• Infantile speech

• speech error
• Spoonerism
• Malapropism
• Mispronunciation

• aphasia
• Aphasiology
• Speech disorder
• Dysnomia disorder
• Aprosodia
• Dysprosody

See also

• psycholinguistics
• FOXP2
• Speech science
• Silent speech interface

References

1. ^ ^{a b c d} Levelt, WJ (1999). "Models of word production.". Trends in Cognitive Sciences 3 (6): 223–232. doi:10.1016/S1364-6613(99)01319-4. PMID 10354575. http://www.columbia.edu/~rmk7/HC/HC_Readings/Levelt.pdf. 
2. ^ Garnham, A, Shillcock RC, Brown GDA, Mill AID, Culter A (1981). "Slips of the tongue in the London–Lund corpus of spontaneous conversation". Linguistics 19 (7–8): 805–817. doi:10.1515/ling.1981.19.7-8.805. http://dare.ubn.kun.nl/bitstream/2066/15615/1/6017.pdf. 
3. ^ Oldfield RC, Wingfield A (1965). "Response latencies in naming objects". Quarterly Journal of Experimental Psychology 17 (4): 273–281. doi:10.1080/17470216508416445. PMID 5852918. 
4. ^ Bird, H; Franklin, S; Howard, D (2001). "Age of acquisition and imageability ratings for a large set of words, including verbs and function words". Behavior Research Methods, Instruments, & Computers 33 (1): 73–9. doi:10.3758/BF03195349. PMID 11296722. http://brm.psychonomic-journals.org/content/33/1/73.full.pdf. 
5. ^ Weinberg, B; Westerhouse, J (1971). "A study of buccal speech". Journal of Speech and Hearing Research 14 (3): 652–8. PMID 5163900. 
6. ^ McNeill D (2005). Gesture and Thought. University of Chicago Press. ISBN 978-0226514635. 
7. ^ ^{a b c d} Levelt WJM (1989). Speaking: From Intention to Articulation. MIT Press. ISBN 978-0262620895. 
8. ^ ^{a b c} Jescheniak JD, Levelt WJM (1994). "Word frequency effects in speech production: retrieval of syntactic information and of phonological form". Journal of Experimental Psychology: Learning, Memory, and Cognition 20 (4): 824–843. doi:10.1037/0278-7393.20.4.824. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.133.3919&rep=rep1&type=pdf. 
9. ^ Indefrey, P; Levelt, WJ (2004). "The spatial and temporal signatures of word production components". Cognition 92 (1–2): 101–44. doi:10.1016/j.cognition.2002.06.001. PMID 15037128. 
10. ^ Booth, JR; Wood, L; Lu, D; Houk, JC; Bitan, T (2007). "The role of the basal ganglia and cerebellum in language processing". Brain Research 1133 (1): 136–44. doi:10.1016/j.brainres.2006.11.074. PMC 2424405. PMID 17189619. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2424405. 
11. ^ ^{a b} Ackermann, H (2008). "Cerebellar contributions to speech production and speech perception: psycholinguistic and neurobiological perspectives". Trends in Neurosciences 31 (6): 265–72. doi:10.1016/j.tins.2008.02.011. PMID 18471906.