Speech production

Speech production is the process by which thoughts are translated into speech. This includes the selection of words, the organization of relevant grammatical forms, and then the articulation of the resulting sounds by the motor system using the vocal apparatus. Speech production can be spontaneous such as when a person creates the words of a conversation, reactive such as when they name a picture or read aloud a written word, or imitative, such as in speech repetition. Speech production is not the same as language production since language can also be produced manually by signs.

In ordinary fluent conversation people pronounce roughly four syllables, ten or twelve phonemes and two to three words out of their vocabulary (that can contain 10 to 100 thousand words) each second.^[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 are abstract.^[3][4]

Normally speech is created with pulmonary pressure provided by the lungs that generates sound by phonation through 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 tract. An example of such alaryngeal speech is Donald Duck talk.^[5]

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

The development of speech production throughout an individual's life starts from an infant's first babble and is transformed into fully developed speech by the age of five.^[7] The first stage of speech doesn't occur until around age one (holophrastic phase). Between the ages of one and a half and two and a half the infant can produce short sentences (telegraphic phase). After two and a half years the infant develops systems of lemmas used in speech production. Around four or five the child's lemmas are largely increased; this enhances the child's production of correct speech and they can now produce speech like an adult. An adult now develops speech in four stages: Activation of lexical concepts, select lemmas needed, morphologically and phonologically encode speech, and the word is phonetically encoded.^[7]